The effects of fast neutron irradiation on the electrical and optical properties of Li (3 at%) doped ZnSnO (ZTO) thin films fabricated using a sol-gel process are investigated. From the results of Li-ZTO TFT characteristics according to change of neutron irradiation time, the saturation mobility is found to increase and threshold voltage values shift to a negative direction from 1,000 s neutron irradiation time. X-ray photoelectron spectroscopy analysis of the O 1s core level shows that the relative area of oxygen vacancies is almost unchanged with different irradiation times. From the results of band alignment, it is confirmed that, due to the increase of electron carrier concentration, the Fermi level (EF) of the sample irradiated for 1,000 s is located at the position closest to the conduction band minimum. The increase in electron concentration is considered by looking at the shallow band edge state under the conduction band edge formed by fast neutron irradiation of more than 1,000 s.

This study demonstrates the effect of addition of Fe particles of different sizes on the critical properties of the superconductor MgB2. Bulk MgB2 is synthesized by ball milling Mg and B powders with Fe particles at 900oC. When Fe particles with size less than 10 μm are added in MgB2, they easily react with B and form the FeB phase, resulting in a reduction in the amount of the MgB2 phase and deterioration of the crystallinity. Accordingly, both the critical temperature and the critical current density are significantly reduced. On the other hand, when larger Fe particles are added, the Fe2B phase forms instead of FeB due to the lower reactivity of Fe toward B. Accordingly, negligible loss of B occurs, and the critical properties are found to be similar to those of the intact MgB2.

The effects of electron beam(EB) irradiation on the electrical and optical properties of InGaZnO(IGZO) thin films fabricated using a sol-gel process were investigated. As the EB dose increased, the electrical characteristic of the IGZO TFTs changed from semiconductor to conductor, and the threshold voltage values shifted to the negative direction. X-ray photoelectron spectroscopy analysis of the O 1s core level showed that the relative area of oxygen vacancies increased from 14.68 to 19.08 % as the EB dose increased from 0 to 1.5 × 1016 electrons/cm2. In addition, spectroscopic ellipsometer analysis showed that the optical band gap varied from 3.39 to 3.46 eV with increasing EB dose. From the result of band alignment, it was confirmed that the Fermi level(EF) of the sample irradiated with 1.5 × 1016 electrons/cm2 was located at the closest position to the conduction band minimum(CBM) due to the increase of electron carrier concentration

The effect of electron beam (EB) irradiation on the electrical properties of Zn-Sn-O (ZTO) thin films fabricated using a sol-gel process was investigated. As the EB dose increased, the saturation mobility of ZTO thin film transistors (TFTs) was found to slightly decrease, and the subthreshold swing and on/off ratio degenerated. X-ray photoelectron spectroscopy analysis of the O 1s core level showed that the relative area of oxygen vacancies (VO) increased from 10.35 to 12.56 % as the EB dose increased from 0 to 7.5 × 1016 electrons/cm2. Also, spectroscopic ellipsometry analysis showed that the optical band gap varied from 3.53 to 3.96 eV with increasing EB dose. From the results of the electrical property and XPS analyses of the ZTO TFTs, it was found that the electrical characteristic of the ZTO thin films changed from semiconductor to conductor with increasing EB dose. It is thought that the electrical property change is due to the formation of defect sites like oxygen vacancies.

MgB2 bulk superconductors are synthesized by the solid state reaction of (MgB4+xMg) precursors withexcessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The MgB4 precursors are synthesized using (Mg+B) powders. Thesecondary phases (MgB4 and MgO) present in the synthesized MgB4 are removed by HNO3 leaching. It is found thatthe formation reaction of MgB2 is accelerated when Mg excessive compositions are used. The magnetization curves ofMg1+xB2 samples show that the transition from the normal state to the superconducting state of the Mg excessive sam-ples with x=0.5 and x=0.7 are sharper than that of MgB2. The highest Jc-B curve at 5 K and 20 K is achieved forx=0.5. Further addition of Mg decreases the Jc owing to the formation of more pores in the MgB2 matrix and smallervolume fraction of MgB2.

The crystallization effects of boron (B) powder on the phase, full width at half maximum (FWHM) values, and critical properties were investigated for in-situ reacted MgB2 bulk superconductors. The semi-crystalline B powder was heat-treated at different temperatures of 1000, 1300 and 1500˚C for 5 hours in an Ar atmosphere. Then, using as-received and heat-treated B powders, the MgB2 samples were prepared at 600˚C for 40 hours in an Ar atmosphere. As the heat-treatment temperature of the B powder increased, both the particle size of the B powder and crystalline phase increased. In the case of MgB2 samples using B powders heat-treated at above 1300˚C, unreacted magnesium (Mg) and B remained due to the improved crystallinity of the B powder. As the heat-treatment temperature of B powder increased, the critical current density of MgB2 decreased continuously due to the reduction of grain boundary density and superconducting volume caused by unreacted Mg and B.

Large single grain Gd1.5Ba2Cu3O7-y (Gd1.5) bulk superconductors were fabricated by a top-seeded melt growth (TSMG) process using an NdBa2Cu3O7-y seed. The seeded Gd1.5 powder compacts with a diameter of 50 mm were subjected to the heating cycles of a TSMG process. After the TSMG process, the diameter of the single grain Gd1.5 compact was reduced to 43 mm owing to the volume contraction during the heat treatment. The superconducting transition temperature (Tc) of the top surface of the single grain Gd1.5 sample was as high as 93.5 K. The critical current densities (Jcs) at 77 K and 1T and 1.5 T were in ranges of 25,200-43,900 A/cm2 and 10,000-23,000 A/cm2, respectively. The maximum attractive force at 77 K of the sample field-cooled using an Nd-B-Fe permanent magnet (surface magnetic field of 0. 527 T) was 108.3 N; the maximum repulsive force of the zero field-cooled sample was 262 N. The magnetic flux density of the sample field-cooled at 77 K was 0.311T, which is approximately 85% of the applied magnetic field of 0.375 T. Microstructure investigation showed that many Gd2BaCuO5 (Gd211) particles of a few μm in size, which are flux pinning sites of Gd123, were trapped within the GdBa2Cu3O7-y (Gd123) grain; unreacted Ba3Cu5O8 liquid and Gd211 particles were present near the edge regions of the single grain Gd1.5 bulk compact.

The effects of nano addition to superconducting properties of processed superconductors was examined. 0.1 wt.% and 1 wt.% nano powders were mixed with boron and magnesium powders by ball milling. The powder mixtures were made into pellets by uniaxial pressing. The pellets were heat-treated at in argon atmosphere for formation. It was found by powder X-ray diffraction that the raw powders were completely converted into after the heat treatment. The superconducting transition temperature () and critical current density (), estimated from susceptibility-temperature and curves, were decreased by nano addition. The and decrease by nano addition are attributed to the incorporation of iron and carbon with lattices (Fe substitution for Mg and C substitution for B) due to the high reactivity of the nano powder.

Ni-W(1-5 at.%) alloy rods were made by powder metallurgy process including powder mixing, compacting and subsequent sintering. Ni and W powder of appropriate compositions were mixed by a ball milling and isostatically pressed in a rubber mold into a rod. The compacted rods were sintered at at a reduced atmosphere for densification. The lattice parameters of Ni-W alloys were estimated by a high resolution neutron powder diffractometer. All sintered rods were found to have a face centered cubic structure without any impurity phase, but the diffraction peak locations were linearly shifted with increasing W content. The lattice parameter of a pure Ni rod was which is consistent with the value reported in JCPDS data. The lattice parameter of N-W alloy rods increased by for 1 atomic % of W, which indicates the formation of a Ni-W solid solution due to the substitution of nickel atoms by tungsten atoms of larger size.

Carbon was known to be one of effective additives which can improve the flux pinning of at high magnetic fields. In this study, glycerin was selected as a chemical carbon source for the improvement of critical current density of . In order to replace some of boron atoms by carbon atoms, the boron powder was heat-treated with liquid glycerin. The glycerin-treated boron powder was mixed with an appropriate amount of magnesium powder to composition and the powder pallets were heat treated at for 30 min in a flowing argon gas. It was found that the superconducting transition temperature of prepared using glycerin-treated boron powder was 36.6 K, which is slightly smaller than (37.1 K) of undoped . The critical current density of was higher than that of undoped and the improvement effect was more remarkable at higher magnetic fields. The , decrease and increase associated with the glycerin treatment for boron powder was explained in terms of the carbon substitution to boron site.

The mother Ni-W (1-5 wt.%) alloy billets for coated conductor substrate were fabricated by powder metallurgy process. The tensile test results for the sintered Ni-W rods showed the increase of mechanical strength and decrease of ductility with increasing W content due to the solid solution hardening. All the fracture surfaces of the tested specimens showed the typical ductile fracture mode of dimple rupture due to the local necking. The Ni-W alloy billets were made into tape by cold rolling. After the appropriate heat treatment for recrystallization, the brass texture formed by the cold rolling was converted to the complete cube texture. The in-plane and out of plane texture of the tapes estimated by x-ray pole figure were smaller than 9 degree and 7 degree, respectively. The effect of the W addition on the texture development seems not to be significant.