Magda Metskhvarishvili

By World Health Organization’s International Agency for Research on Cancer (IARC) radon was classified as the A-class carcinogen. Radon is responsible for approximately half of average annual personal effective dose from all natural sources of ionizing radiation. The risk of lung cancer caused by radon exposure to the human body increases with increasing of radon concentration. In particular, at a concentration of 100-200 Bq/m³ in residential apartments and working buildings, the risk of lung cancer increases by 20%, at concentrations of 400-799 Bq/m³ by 40%, and at concentrations above 800 Bq/m³ by ~100%. Also, this risk depends on the duration of exposure of radon and its decay products.

     The problem discussed in this is urgent for Georgia, mostly because of the geologic formations of country are characterized by high content of uranium, and many buildings are constructed with local materials. Exposure with radon inside the buildings in Georgia is potentially a serious problem.

     Radon concentrations in the air inside buildings can vary greatly among different regions and different homes. In addition, they are characterized by a wide range of time variations. Due to the fact that radon eminence occurs from the soil under the house, the highest concentrations of radon in buildings are observed in basements and apartments located on the lower floor. Preliminary results of radon concentrations in residential and public areas in some districts of Tbilisi show that further investigations are needed that will involve a larger-scale measurements and more extensive studies of this problem.

Keywords: radon, carcinogen, exposure, radiation.

In High-temperature ceramics nonlinear and irreversible phenomena under weak magnetic fields, considerably smaller than the first critical field of the grain, have been observed. The principle cause of an existence of nonlinear phenomena is Josephson junctions between the granules. It could also exist between crystallites in polycrystals, especially in systems with small coherent length ξ. All high-temperature superconductors belong to such kind of system.

The purpose of the present work is a study of a behavior of nonlinear susceptibility of high-temperature TlBa2Ca2Cu3O8+δ polycrystalline superconductor in small ac (h<1Oe) and dc (H<16 Oe) collinear fields. One of the most interesting results of the theory of a critical state in law field case h<<H is prediction of existence of big numbers of high harmonics of induction. Thus, in weak fields, when h=const, coefficients  and  are the same order of magnitude and are defined only by a number of harmonics.

We have studied the module of the amplitudes of the high harmonics as function of ac (h), dc (H) fields and temperature (T). Obtained data confirm the applicability of law field electrodynamics to the investigated samples. Our measurements have shown that by varying the constant field from 0 to 16 Oe, amplitude of the odd harmonic is linearly increasing. Such a behavior of the harmonics corresponds to the following model dependence: jc(H)=jo/(1+h/Ho). As a result we could conclude that in TlBa2Ca2Cu3O8+δ polycrystalline superconductor under a law field Kim-Anderson model is realized.

Acknowledgments:This work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number: CARYS-19-1832, Project title: Innovative Cryostat for Studying High-temperature Superconductors.

Thallium- and mercury-based superconductors, generates considerable interest because these systems set records in transition temperature in superconductivity state. The formula unit and crystal structure of the TlBa2Can−1CunO2n+2+δ similar to that of the HgBa2Can−1CunO2n+2+δ systems, where (n) is the number of adjacent Cu-O layers. Mercury- and thallium are very toxic, volatile at high temperature, and what is more important for this family, to achieve high purity superconductivity phase, critically depends on the used precursor and synthesis conditions. The paper presents the comparative analysis of the Sol-gel (SG) and solid-state reaction (SSR) route for the synthesis of precursors for thallium-based superconductors. Samples were prepared a two-step method and by sealed quartz tube technique in ambient pressure. We could conclude that the, using the wet chemistry offers some advantages in comparison with the classical solid-state ceramics processing, especially, better chemical homogeneity and higher reactivity of the precursor powder. Acknowledgements: This work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number: FR/261/6-260/14, Project title: Sol-gel Methods and Polymerization for synthesized Tl-based Polycrystalline Superconductors.

We report high harmonic generation to study the inter-grain superconducting properties of hightemperature TBCCO and Chevrel-phase MSI polycrystalline superconductors. As is well known, high harmonics arose due to the nonlinear magnetization caused by the penetration of the magnetic flux through the grain boundaries. The nonlinear response study is fundamentally different from the measurement of linear susceptibility. If, in the linear case, the response to an external influence is investigated at the same frequency at which the entire measuring circuit is excited. In the higher harmonic method, the measurements are carried out at frequencies other than the main one. That can say that the measurement takes place as if on a zero background. In our experiment, we discuss when collinear constant and variable fields H(t)=H+hcosωt are applied to the sample. In this case, could be expanded induction B(t) into the Fourier series. Errors in high harmonics measurement could be as high as ∼2 % when the measuring signal is lower than 0.2 μV. However, the error does not exceed 0.5 % for higher amplitudes. Measurements have been mainly performed at 20 kHz frequency and in the range of fields 0≤h≤1 and 0≤H ≤25 Oe. As a result, experimental investigations have shown that nonlinear magnetic responses from Josephson

medium are quite different in polycrystalline samples of high-Tc and Chevrel-phase materials. The High-Tc materials are better described by Kim-Anderson model, where the critical current depends on the external magnetic field and even harmonics are observed in dc fields. On the other

hand, Chevrel-phase materials follow the classical Bean critical state model, when the current does not depend on the field and even harmonics are not observed. Acknowledgments This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG), under GENIE project, grant number: CARYS-19-1832, Project title: Innovative Cryostat for Studying

High-temperature Superconductors.

The TlBa2Ca2Cu3Oy high-temperature superconductor shows superconducting transition temperature Tc above 115 K when these are prepared at ambient conditions and when under high pressures, the critical temperature can reach 133.5 K. These characteristics make the Tl-1223 phase a potentially valuable material for producing superconducting wires, tapes, and thin-films. Formation of the Tl-based superconducting materials critically depends on the used precursor and synthesis conditions. Using the wet chemistry offers some advantages in comparison with the classical solid-state ceramics processing, especially, better chemical homogeneity and higher reactivity of the precursor powder.

The present study devoted to synthesizing the precursors by two different methods. It is must note that for both sol-gel and solid-state reaction ways, oxides and carbonate-containing materials were used as starting materials. For the sol-gel route, poly(vinyl alcohol)/poly(vinyl acetate) was used as the complexing agent. In presenting work also investigated precursors properties dependence on heat treatments. A characterization of precursors obtained by the SG and SSR approaches on the superconducting parameters of TlBa2Ca2Cu3DyxO8+δ is investigated, analyzing comparatively the results of their X-ray diffraction, FTIR analysis, ac magnetic susceptibility, and transport critical current densities. The phase method was used to study the real parts -4πχ’ of the linear susceptibility. For the measurements of intergranular critical current densities, we used the method of high harmonics.

As a result, we could conclude that the sol-gel process has the potential advantage over the solid-state reaction method, for achieving homogeneous mixing of the component cations on the atomic scale but also higher reactivity of the precursor powder, and in the result leads to the promotion of the high-Tc phase and enhancement of the transport critical current densities Jc.

Acknowledgments

This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG), under GENIE project, grant number: CARYS-19-1832, Project title: Innovative Cryostat for Studying High-temperature Superconductors.

"High temperature polycrystalline superconductors are associated with the existence of superconductivity in each grain, whose parameters are similar to a bulk single crystal. Between the grains there are weak Josephson junctions, which determine the superconducting properties of the whole system. For the Josephson junctions in low fields, less than first critical field of the grains Hc1, a lot of irreversible and nonlinear phenomena are observed. These phenomena are characterized by the presence of high harmonics. In high temperature polycrystalline superconductors when ultraweak ac excitation field is immersed, only odd harmonic are generated. However, when dc magnetic field is applied along with the ac magnetic field, even harmonics are generated. The generation of higher harmonic components and nonlinearity of magnetization has been explained with critical state models.

The purpose of the present work is to study the high harmonics response of Mo6S6I2 polycrystalline superconductor in ultra-weak magnetic fields in order to understand granularity nature of the Chevral phase polycrystalline superconductors. This choice was made because the ternary molybdenum chalcogenide, so called Chevral phase superconductors behave like the high temperature oxide superconductors. The Ginsburg-Landau parameter κ≈100 is large and the coherence length very short ξ ≈ 2–3 nm. Inasmuch in Chevral phase superconductors ξ is of order of several angstroms, therefore there are grounds for expecting that for such values of ξ any, even a small, defect can act like a Josephson junction. Our experimental results have shown that, very weak ac magnetic fields of order of millioersteds do indeed penetrate into the Mo6S6I2 polycrystalline superconductor and nonlinear magnetic response are analyzed in the frame work of Bean’s critical state model.

This work was supported by Shota Rustaveli National Science Foundation of Georgia (SRNSFG), under GENIE project, grant number: CARYS-19-1832, Project title: Innovative Cryostat for Studying High-temperature Superconductors."

Mercury- and thallium-based superconductors having the highest critical temperature, whenHg1223 are prepared at ambient conditionsTc≈135 K [1] andTc≈164 K at under high pressures (30 GPa) [2].Transition temperature nonsubstitutedphase of Tl-1223 is Tc≈115K [3] and Tc≈130 Kat pressures(3.5 GPa)[4]. The formula unit and crystal structure of the TlBa2Can−1CunO2n+2+δsystem similar to that of the HgBa2Can−1CunO2n+2+δsystem, where (n) is the number of adjacent Cu-O layers. Mercury- and thallium are very toxic, volatile at high temperature and what is more important for this family, to achieve high purity superconductivity phase, critically depends on the used precursor and synthesis conditions. Preparation of high purity and reaction ability precursor, in the various articles, was solved by diverse methods. We have presented the preparation of Tl-1223 high-temperature superconductors by sealed quartz tube technique. For the synthesis samples, we used the two-step method. In the first stage were prepared, multiphase precursors in the second stage where Tl2O3 was added. Precursors were prepared by two methods, sol-gel, and solid-state reaction methods and examined the influence of heat treatment

on precursors. These results showed that to obtain high-purity precursors for SG methods sufficiently heat treatments at 915oC temperatures and for SSR methods 945oC. The diamagnetic onset temperature of the superconducting transition for the samples prepared by precursors SG at 915oC and SSR at 945 oC is about T=120 K and full screening of applied ac magnetic fields observed at T≈ 102 K and T≈92

K, respectively. The unlike SG method in SSR samples clearly shows a two-step decrease with T, which reflects the flux shielding from and between the grains. As a result, we could conclude that theSG method demonstrated as a successful alternative to SSR methods allowing a faster production of the precursor powders, without any carbonate contamination. Acknowledgements: this work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number: FR/261/6-260/14, Project title: Sol-gel Methods and Polymerization for synthesized Tl-based Polycrystalline Superconductors.

 normal conditions Tc≈135K and Tc≈165K under the external pressure. This peculiar property makes the Hg-1223 phase as an invaluable material for its practical utilization. We report the effects of the edition of I2O5 on the electric and magnetic properties in Hg-1223 high temperature superconductors. Samples with composition HgBa2Ca2Cu3IxO8+δ (x=0.0-1.6 wt.%) were prepared by the two-step method. In the first step, we synthesized Ba:Ca:Cu=2:2:3 precursors by sol-

gel method. In second step on precursor we added HgO and I2O5 and finale synthesis of samples was carried out in a sealed quartz tube. The effect of I2O5 doping on Hg-1223 system has been studied by the: X-ray diffraction with CuKa radiation, FTIR Spectrometer using the KBr disc technique, ac susceptibility χ’ and the third harmonics response. We found that Iodine enhances volume fraction of the Hg-1223 superconducting phase and the value of the transport critical current densities Jc. This work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number:

217524, Project title: Influence of the polymerization and various dopants on the Hg-1223

superconductive properties.

Formation of the Hg-based superconducting materials critically depends on the used precursor and synthesis conditions. Using the wet chemistry offers some advantages in comparison with the classical solid-state ceramics processing, especially, better chemical homogeneity and higher reactivity of the precursor powder. On this basis the influence of Ba2Ca2Cu3Oy precursor on the synthesis and properties of HgBa2Ca2Cu3Oy has been examined. HgBa2Ca2Cu3Oy superconducting samples were prepared by a two-step method. In the first step, was prepared Ba:Ca:Cu=2:2:3 multiphase ceramic precursors, for comparisons two methods we synthesized precursors by sol-gel method using polymerization (SGMP) and as well as ordinary solid-

state reaction method (SSRM). In second step on both samples HgO was added and finale synthesis of HgBa2Ca2Cu3Oy was carried out in a sealed quartz tube.

We note that for both methods, starting materials was used powders materials (Sigma-Aldrich) of BaO (99.98%), CaCO3 (99.0%) and CuO (99.999%). The synthesis of a precursor by the sol-gel method was used acetic and nitric acid for dissolved oxide and poly(vinyl alcohol)/poly(vinyl acetate) (PVA)/(PVAc) (≥ 99%) as a complexing agent.

The prepared patterns were characterized by X-ray diffraction (XRD, Dron-3M) with CuKa radiation. Ac susceptibility and high harmonic response of samples are measured in weak ac and dc magnetic fields. Fig. 1 we show the temperature dependences of the real part of ac susceptibility of the samples prepared by SGMP and SSRM. As a result we could conclude that, in comparison with SSRM in SGMP sample we found highest value of the transport critical current densities Jc.

This work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number:

217524, Project title: Influence of the polymerization and various dopants on the Hg-1223

superconductive properties

As is known, more than half of the dose of population exposure to natural radiation is connected with radioactive gas radon. This gas constantly and everywhere allocates from Earth interior. A radon source are rocks (first of all uranium-containing), arising from which radon propagates in soil, whence gets to atmosphere, underground and surface waters, indoor air of premises.

Researches were carried out in 7 locations in the outlying districts of city Tbilisi (in Tbilisi artesian basin) and 3 locations around city Mtskheta (in Kartli artesian basin) in the region of arrangement of sources of drinking (tap) water of Tbilisi.

Apparently from results, on the average values of soil radon in the territory of Tbilisi artesian basin is considerably greater than in the territory of Kartli artesian basin.

On the basis of the obtained results there have been created the radiation maps of the soil air of the investigated Tbilisi and Kartli Artesian basins. There has been carried out comparison of our results with literature data.

Studding multipoles of g-radiation and determination of share of admixture in the case of mixed g-transition is necessary to study the physical properties of the excited levels of nuclei and to verify different theoretical nuclear models. It is also important to investigate the forms of conversion lines and determine their half-widths. Accumulated quantitative materials give possibility to receive new information about nuclei and atomic levels. In the paper, the results of investigations of internal conversion electron (ICE) spectrum of 169Tm 93.61 keV g-transition are presented. Measurements were carried out by means of magnetic beta-spectrometer with 0.04 % high resolution. Forms of L I, L II, and L III conversion lines are studied and relative amounts of their expansions are measured. Mean quantity of d 2 from the established internal conversion coefficients (ICC) are calculated d 2 = 0.034 ± 0.003. Average significance of the share of electric quadrupole admixture a = 3.3 ± 0.3 % are found, which corresponds to M1+3.3%E2 mixed -transition.

We present the effects of the edition of Ag2O on the electric and magnetic properties in Hg-based high temperature superconductors. Samples with composition HgBa2Ca2Cu3AgxOy (x=0.0-1.2 wt.%.) were prepared by the two-step method. In the first step, was prepared Ba:Ca:Cu=2:2:3 multiphase ceramic

precursors, for starting materials was used powders materials (Sigma-Aldrich) of BaCO3 (99.98%), CaCO3 (99.0%) and CuO (99.999%). The synthesis of a precursor by the sol-gel method was used acetic and nitric acid for dissolved oxide and ε-Caprolactam (99%) as a complexing agent. In second step on precursors HgO and Ag2O was added and finale synthesis of HgBa2Ca2Cu3AgxOy was carried out in a sealed quartz

tube. The prepared patterns were characterized by X-ray diffraction (XRD, Dron-3M) with CuKa radiation. Ac susceptibility and High harmonic response of polycrystalline superconductors un-doped and Silver-doped samples are measured in the presence of small ac excitation field and dc magnetic field applied on it. Critical state models are used to explain the nonlinear magnetic response in polycrystalline

superconductors. Finally, we observed that, the low level Silver doping enhances on the transport critical current densities Jc. Acknowledgments

This work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number: 217524, Project title: Influence of the polymerization and various dopants on the Hg-1223 superconductive properties.

We report the effects of the edition of P2O5 on the electric and magnetic properties in Tl-based high temperature superconductors. Samples with composition TlBa2Ca2Cu3PxO8+δ (x=0.0-1.8 wt.%) were prepared by the two-step method. In the first step, we synthesized precursors by sol-gel method using poly(vinyl alcohol)/poly(vinyl acetate) (PVA/ PVAc) as a complexing agent. In second step on precursor we added Tl2O3 and P2O5 and finale synthesis of samples was carried out in a sealed quartz tube. The prepared patterns were characterized by X-ray diffraction with CuKa radiation. Analysis of X-ray data, showed that the in phosphorus-doped samples observed the single phase 95 % volume, whereas for

non-doped observed 75% of the Tl-1223 phase. Ac susceptibility and high harmonic response of undoped and phosphorus-doped samples are measured in weak ac and dc magnetic fields (10−2 ≤ h ≤1 Oe, 0 ≤ H ≤ 12 Oe.). As a result, we observed that, the phosphorus pentoxide doping enhances the chemical and physical properties of Tl-based materials. Acknowledgements This work was supported by Shota Rustaveli National Science Foundation (SRNSF), grant number: FR/261/6-260/14.

The influence of Ba2Ca2Cu3Ox precursor on the synthesis and properties of Tl-based superconductors has been examined. TlBa2Ca2Cu3Oy superconducting samples were prepared by a two-step method. In the first step, was prepared Ba:Ca:Cu=2:2:3 multiphase ceramic precursors, for comparisons two methods we synthesized precursors by sol-gel method (SG) using poly (vinyl alcohol)/poly (vinyl acetate) (PVA/ PVAc) and as well as ordinary solidstate reaction method (SSR). In second step on both samples Tl2O3 was added and finale synthesis of TlBa2Ca2Cu3Oy was carried out in a sealed quartz tube. We note that for both methods, starting materials was used powders materials (Sigma- Aldrich) of BaO (99.98%), CaCO3 (99.0%) and CuO (99.999%). The synthesis of a precursor by the sol-gel method was used acetic and nitric acid for dissolved oxide and PVA/ PVAc as a complexing agent. The prepared patterns were characterized by X-ray diffraction (XRD, Dron-3M) with

CuKa radiation. Ac susceptibility and high harmonic response of samples are measured in weak ac and dc magnetic fields. As a result, we could conclude that, in comparison with SSR in SG sample we found highest value of the transport critical current densities Jc. Acknowledgements: This work is supported by the Georgian Shota Rustaveli National Science Foundation. Project Number: FR/261/6-260/14.

Formation of the Tl-based superconducting materials critically depends on the used precursor and synthesis conditions. Using the wet chemistry offers some advantages in comparison with the classical solid-state ceramics processing, especially, better chemical homogeneity and higher reactivity of the precursor powder. On this basis the nfluence of Ba2Ca2Cu3Oy precursor on the synthesis and properties of TlBa2Ca2Cu3Oy has been examined. TlBa2Ca2Cu3Oy superconducting samples were prepared by a two-step method. In the first step, was prepared Ba:Ca:Cu=2:2:3 multiphase ceramic precursors, for comparisons two methods we synthesized precursors by sol-gel method using polymerization (SGMP) and as well as ordinary solid-state reaction method (SSRM). In second step on both samples Tl2O3 was added and finale synthesis of TlBa2Ca2Cu3Oy was carried out in a sealed quartz tube. We note that for both methods, starting materials was used powders materials(Sigma- Aldrich) of BaO (99.98%), CaCO3 (99.0%) and CuO (99.999%). The synthesis of a precursor by the sol-gel method was used acetic and nitric acid for dissolved oxide and EDTA acid (≥ 99%) as a complexing agent. For polymerization we used Acrylamide monomers (≥ 99%); N,N’ – Methylenebis(acrylamide) (99%); 2,2-Diethoxyacetophenone (>95%). The prepared patterns were characterized by X-ray diffraction (XRD, Dron-3M) with CuKa radiation. Ac susceptibility and high harmonic response of samples are measured in weak ac and dc magnetic fields. Fig. 1 we show the temperature dependences of the real part of ac susceptibility of the samples prepared by SGMP and SSRM. As a result we could conclude that, in comparison with SSRM in SGMP sample we found highest value of the transport critical current densities Jc. Acknowledgements This work is supported by the Georgian Shota Rustaveli National Science Foundation. Project Number: FR/261/6-260/14.

Abstract Book p. 134.  The HgBa2Ca2Cu3O8+δ high temperature superconductor shows superconducting transition temperature Tc above 135 K and Tc≈165K under the external pressure. These characteristics make the Hg-1223 phase a very attractive material for producing superconducting wires, tapes, and thin-films. Therefore, creation simpler and reliable technologies for synthesized high stability Hg-1223 phase are very important subjects

in order to achieve the large-scale technological applications of mercury-based superconductors.

We report the wet chemistry methods for preparation Hg-based polycrystalline superconductors. For synthesized Hg-1223 samples, we used two-step method. In the first stage non-mercury containing precursor was prepared before proceeding to the second stage where HgO was added to the precursor before final sintering. The synthesis of Ba2Ca2Cu3Oy is carried out by dissolving separately CaCO3 in acetic acid, CuO in ammonium chloride and BaCO3 in distilled water. The solutions are mixed afterward in the stoichiometric ratio. To this solution were added poly(vinyl alcohol) (PVA). The solution dried at 180oC temperature for 12 h and after obtained gel was dreaded at 300oC. The xerogels are then homogenised in an agate mortar and calcined at 750oC, during 4 h in a muffled furnace. The obtained precursor is then mixed with HgO in nominal stoichiometric quantity. The resulting powder is pelletized and inserted in a quartz tube that is closed under vacuum. These pellets were sintered in furnace at 800oC for 6 hours. The structure of the obtained materials was determined by XRD. Transition temperature was measured by ac susceptibility and critical currents density Jc by high harmonic methods. Finally, including poly(vinyl alcohol) in preparation precursor Ba2Ca2Cu3Oy we observed single-phase and purity high temperature Hg-1223 phase. This work has been fulfilled by financial support of the Shota Rustaveli National Science Foundation, Grant No. FR/423/6-260/12.

Abstract Book p. 284. We report the effects of the edition of As2O3 on the electric and magnetic properties in Hg-based high temperature superconductors. Samples with composition HgBa2Ca2Cu3AsxO8+δ (x=0.0-1.2 wt.%) were prepared by the two-step solid-state reaction method. In the first step highly pure powders of BaO, CaCO3 and CuO were mixed in the stoichiometric ratio Ba:Ca:Cu=2:2:3 and then they were mixed and ground carefully in an agate mortar. The resulting powder mixture was calcined in an alumina crucible in air with four intermediate grindings at 900 oC for 60 h. In the second step the Ba–Ca–Cu–O precursor was mixed with HgO and As2O3 powders according to the composition HgBa2Ca2Cu3AsxO8+ δ

(where x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 wt.%) and After final grinding the powder was pressed into a disc-shaped pellet 6 mm in diameter, and 2 mm thick, by using a hydraulic press under a pressure of 5 ton/cm2. The pellets were put in a quartz tube and from quartz tube was evacuated up to 10-4 Torr and sealed. Thereafter, quartz tube was inserted into a programmed muffle furnace and heated to 860oC and held at this temperature for 12 h. Finally, the samples were oxygenated in furnace at 300oC in air 15 h. The prepared patterns were characterized by X-ray diffraction (XRD, Dron-3M) with CuKa radiation. Ac susceptibility and high harmonic response of un-doped and Arsenic-doped samples are measured in weak ac and dc magnetic fields (10−2 ≤ h ≤1 Oe, 0 ≤ H ≤ 12 Oe.). Critical state models are used to explain the nonlinear magnetic response. As a result we could conclude that, the low level Arsenic doping enhances the transport critical current densities Jc.

This work has been fulfilled by financial support of the Shota Rustaveli National Science Foundation, Grant no. FR/423/6-260/12.

With the aim to generate a nano-dimentional atom clusters by the irradiative method, the influence of irradiation by the particles of various energies and types on the nature of radiation induced defects originated in n-Si crystals has been investigated in the work. For the investigation we used the n-type Si crystals with the electron concentration 6.10^13 cm^(-3). We irradiated the crystals in size of 1´3´10 mm at 300K temperature by the electrons with the energy of 2 and 8 Mev. The difinite part of the samples we have irradiate by the protons with the energy of 25 Mev. The method of isochronal baking is used. We oerformed the baking within the interval of 80-600oC within the temperature interval by step of 10oC. 10 minutes are defined for time baking. After each cycle of baking the pecific resistivity of the samples has been measured by means of two probe methods, and the concentration of electrons were measured within the temperature interval 77-300 K. By means of these data we were calculating the Hoall mobility. The photo-Hall method has been applied in the work.

Abstract book, p.564  We are reporting the effects of the addition of Sb2O3 on the electric and magnetic properties of Bi-based high temperature superconductors. Samples with composition Bi1.7Pb0.3Ca2Sr2Cu3SbxOy (x=0.00, 0.02, 0.04, 0.06, 0.08; 0.10, 0.12) were prepared by the solid-state reaction method. These powders were first well mixed and grounded in an agate mortar. The powdered mixture was calcined in air at 800°C for 10 h. Calcined powders were grounded and recalcined at 810, 820, 830, 840°C and during 10 hours on each temperature powders were grinding again. Finally, powders were grounded and pressed to form of pellets with 10 mm diameter and 1.5 mm thickness under a pressure of 900 MPa. These pellets were sintered in furnace at 850 °C for 20 hours in an air atmosphere. The structure of the obtained materials was determined by XRD. Ac susceptibility and high harmonic response of polycrystalline superconductors un-doped and Antimony-doped patterns were measured in the presence of small ac excitation field and dc magnetic field applied on them. Critical state models were used to explain the nonlinear magnetic response in polycrystalline superconductors and found that the low field odd harmonic response qualitatively reasonably well within the Anderson-Kim regime. Finally, we observed that, the presence of antimony oxide made the system more reactive and enhanced the kinetic of reaction, as well as the promotion of the high-Tc phase.

Abstract book, p. 893   We have studied harmonic generation in the ultra-weak magnetic fields of bulk sample of the Mo6S6I2 polycrystalline superconductor. Dependence of the odd and even harmonics of magnetization on the dc magnetic field, amplitude of the ac magnetic field and temperature was investigated. We observe very high order of odd harmonics generated in H=0 and in H≠0. Even harmonics are not observed under 20 Oe magnetic fields. Also, our experiments show that the amplitudes of the odd harmonics do not depend on the magnitude of the dc field. Numerical results of our experiments have shown that the Bean critical state theoretical model is preferable for investigation of the sample.

Abstract-Book, p. 50   Among all of the known high-Tc superconductors the Hg-based cuprate superconductors HgBa2Ca2Cu3Oy have the highest critical temperature Tc≈135K. This peculiar property makes the Hg-1223 phase as an invaluable material for its practical utilization. Preparation of Hg-based cuprate superconductors by the solid state reaction method are labor-consuming (expensive, multi-stage) also needed high temperature and long times for observation chemical homogeneity and chemical reactivity. We report the sol-gel methods for preparation Hg-based

polycrystalline superconductors. The basic idea of sol–gel is to start from a solution of cations and to jellify it by polymerization. The synthesis of Ba2Ca2Cu3Oy is carried out by dissolving separately CaCO3, CuO in nitric acid and BaCO3 in acetic acid. The solutions are mixed afterward in the stoichiometric ratio. The cations Cu2+ in the solution are complex with addition of acid-EDTA: (H4Y)=[CH2N(CH2-COOH)2]2 and the pH was adjusted ≈3 just to dissolve completely the elements into a clear solution. To this solution were added acryl amide monomers, i.e., H2C=CHCONH2 and N,N’-methylenebisacrylamide. A few milligrams of a chemical initiator a,a’-azoisobutyronitrile, i.e., C8H12N4, was added to initiate the polymerization. The gel is

then dried at 120 oC temperature for 12 h. The obtained precursor Ba2Ca2Cu3Oy is then mixed with HgO in nominal stoichiometric quantity. The resulting powder is pelletized and inserted in a quartz tube that is closed under vacuum. These pellets were sintered in furnace at 850 °C for 10 hours. The structure of the obtained materials was determined by XRD. Transition temperature was measured by ac susceptibility and high harmonic methods. Finally, we observed that, the sol–gel processing is efficient and very shortening the superconducting phase formation times. This work has been fulfilled by financial support of the Shota Rustaveli National Science Foundation, Grant No. FR/423/6-260/12, number of contract 31/36.

Abstract book, p.240 PbMo6S8 polycrystalline superconductors have been studied in weak linearly polarized and circularly polarized ac magnetic fields (0-1 Oe) with existence of constant dc field (0-8 Oe). In order to study the behavior of the critical current density of the Josephson junctions in a linearly and circularly polarized ac fields, the method of high harmonics is used. We consider an infinitely large slab in yz-plane having a thickness d along x-axis. We assume that the dc field is directed along z-axis, while the ac field h(t)=coswt lies in yz-plane and makes an angleg with respect to H. In case of rotating ac magnetic field, the dependencies of z and y components of the odd and even harmonics on the inclination angle y are different in the anisotropic and isotropic theoretical models [1]. Numerical results of our Experiments with a linearly polarized oscillating field orientated at various angles to a constant field and also with a rotating oscillating field superimposed on a constant field have shown that the isotropic model is preferable for investigated sample. [1] S. L Ginzburg et al, Supercond. Sci. Technol. 11, 255 (1998).

Abstract book, p.131     A series of compounds with nominal compositions Bi2Sr2Ca1Cu2BxOyandBi1.8Pb0.2Sr2Ca1Cu2BxOy (=0, 0.10, 0.25, 0.50 and 0.75) were synthesized by a standard ceramic technique. In order to examine the influence of the change in oxygen stoichiometry on the critical temperature, both slow cooling in furnace and quenching into liquid nitrogen were applied after annealing. Phase analysis by x-ray diffraction and measurements of electrical resistivity and magnetic susceptibility were carried out. The results show that boron-doped Bi-2212 and Bi(Pb)-2212 samples are characterized by presence of the Bi2Sr2Cu1Oy(2201) phase at x0.25. B2O3 addition enhances the critical temperature of furnace cooled Pb-free (at x=0.10-0.25) and Pb-substituted 2212 (at x=0.10-0.75) HTS. Such behavior seems to be associated with the filling of excess holes in originally overdoped compounds by the additional electrons contributed by B3+ ions. The electrical and magnetic measurements indicated that both the uperconducting volume fraction and critical temperature in the quenched

compounds decrease with increasing dopant concentration. Increase of values of normal state resistivity of the quenched samples in comparison with furnace-cooled, apparently, is caused by the deterioration of connections between superconducting granules, due to occurrence of microcracks in fragile ceramics at a quenching in liquid nitrogen.

Abstract Book, p. 234, In High-temperature ceramics nonlinear and irreversible phenomena under weak magnetic fields, considerably smaller than the first critical field of the grain, have been observed. The principle cause of an existence of nonlinear phenomena is Josephson junctions between the granules. It could also exist between crystallites in polycrystals, especially in systems with small coherent length ξ. All high-temperature superconductors belong to such kind of system. The purpose of the present work is a study of a behavior of linear and nonlinear susceptibility of high-temperature Tl2Ba2Ca2Cu3O10 polycrystalline superconductor in small ac (h<1Oe) and dc (H<8Oe) collinear fields. One of the most interesting results of the theory of a critical state in law field case h << H,h2 (h2 is a field penetrated until the middle of samples) is prediction of existence of big numbers of high harmonics of induction. Thus, in weak fields, when h=const, coefficients n a and n b are the same order of magnitude and are defined only by a number of harmonics. Obtained data confirm the applicability of law field electrodynamics to the investigated samples. A spectrum of the high harmonics has been measured in this paper. From the results is follows that the amplitudes of harmonics are slightly decreasing in proportion to the number of harmonics. From the dependence of the harmonics on the imposed magnetic fields, we could conclude that 1 a and 1 b are related to the real and imaginary parts of linear susceptibility. Moreover, the amplitudes of the third C3 and the fifth C5 harmonics have square dependence on the amplitude of ac. This result is in a good agreement with the theoretical one. In the low field regime [1], the odd harmonics are inversely proportional to a density of a critical current j (H) c 1 and even harmonics are proportional to d/dH (1/ jc (H)) that allows us to determine j (H) c function. Our measurements have shown that by varying the constant field from 0 to 8 Oe, amplitude of the third harmonic is linearly increasing. Such a behavior of the harmonics corresponds to the following model dependence: (jc(H)=jo(1+H/Ho)) As a result we could conclude that in TBCCO polycrystalline superconductor under a law field Kim-Anderson model [2] is realized. [1] S.L. Ginzburg, I.D. Luzianin, I.R. Metskhvarishvili, E.G. Tarovik, V.P. Khavronin, JETP Letters 69, 184 (1999). [2] P. W. Anderson and Y. B. Kim, Rev. Mod. Phys. 36, 39 (1964).

The ac susceptibility and high harmonics response of low and high temperature polycrystalline superconductors is measured in very weak ac and dc magnetic fields. The experimental results agree satisfactorily with the theory of the critical state in the framework of low-field electrodynamics. Experimental data show that the critical current density does not depend on the dc magnetic field for SnMo6S8 and squire dependence exists for YBa2Cu3Oy. 

By means of double focusing sector type magnetic beta-spectrometer with 0.2% resolution and useful solid angle of 0.3% from 4p (in the case of 1´30mm² sizes of radioactive source and inlet opening), arrangement ranges of the ¹⁵¹Eu 153.6keV energy conversion lines was investigated for determination of multipolarity of this transition. Two groups of K, L_I, L_II, L_III conversion lines are observed. From them one group connects to the 153.6keV g-transition and another to 153.3keV g-transition. 153.3keV energy conversion lines were not observed earlier. Experimental ratios of internal conversion coefficients (ICC) on L_I, L_II and L_III shells for both g-transitions were determined. Analogous theoretical significance was received from the table]. Results are given in the table. On the basis of this data are established that 153.6keV g-transition is the mixture of M1 and E2 multipoles. Amount of admixture a of E2 multipole is (13±2)%. 153.3keV g-transition is mixture of M2 and E3 miultipoles with admixture of E3 amounting (6±2)%. This transition happens between the levels of 349.8 and 196.5keV [2]. Quantum characteristics of 196.5keV level equals (3/2)⁺ by [2]. Established by us multipolar compound of 153.3keV (M2+E3) g-transition enables us to confirm that spin of 196.5keV level must be (5/2)⁺. 1. I.M. Band, M.B. Trjaskovskaya. “Tables of Internal Conversion Coefficients of Gamma-ray on K-, L-, M-shells 10£z£104”. L. LIAF, SSSR 1978.

2. R.B. Firestone, V.S. Shirley, C.M. Baglin, S.Y. Frank Chu and J. Zipkin. Table of Isotopes 8th ed (New York, Wiley, 1996).

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