Papers by Keyword: Low Oxygen Partial Pressure

Abstract: We investigated the effect of the donor-doped content on the positive temperature coefficient of resistivity (PTCR) of (Ba_1-xSm_x)TiO₃ (BST) Based Ceramics that were sintered at 1300 °C for 30 min in a reducing atmosphere and re-oxidized at 850 °C for 1 h. The results indicated that the resistance jump first increased and then decreased with an increase of the donor-doped concentration. Moreover, the specimens achieved a low room temperature resistivity of 383.1 Ω·cm at a donor-doped content and exhibited a pronounced PTCR characteristics with a resistance jump of 3.1 orders of magnitude. Furthermore, the RT reisistivity of the samples reduced and increased with the increasing of the donor-dopant content in the range of 0.1−0.5 mol% Sm³⁺. In addition, the effect of the Sm³⁺-doped concentration on the grain size of the ceramics was investigated in our paper.

Abstract: Two chromia forming materials have been exposed to different test gases at low pO2. All used test gases contained hydrogen species in the form of molecular hydrogen and water vapour. To insure the validity of the measured H-profiles H2 was replaced by with D2 and H2O by D2O. The Deuterium profiles in the oxides formed were established using SIMS and GDOES techniques. The profiles were quantified and correlated with the growth rate and the microstructures of the chromia scales formed on in low pO2 test gases. The presence of H2/H2O in the low pO2 test gas alters the properties of thermally growing chromia scales.

Abstract: High critical current density Jc under high magnetic field is required in numerous applications for high temperature superconductor YBa2Cu3O7-δ (Y123). Significant efforts have been made to control sample preparation in view of optimized textures and microstructures. In YBa2Cu3O7-δ superconductor, Jc is limited by grain misalignment and by other defaults like secondary phase (Y211), microcracks... So YBaCuO films were prepared by electrophoretic deposition directly on polycrystalline Ag substrate. Melt textured growth (MTG) in low oxygen partial pressure and cold rolling were performed to YBaCuO samples respectively to improve texture growth of the films and to study deformation effect on the texture. The film obtained by melted growth after rolling has better texture orientation than the film without rolling, and presents higher critical current density.