High-pressure Synthesis And Property Characterization Of Perovskite Structure Materials

Perovskite widely exists in the nature, its name originates from one compound with molecular formula CaTiO₃. Its general chemical formula is ABO₃. In the early days of the perovskite study, bismuth titanate?BiTiO3? was found to be ferroelectric. Hence, materials possessing perovskite structure had greatly caused the people's interests. Then Giant magnetoresistance in manganites perovskite and high temperature superconductor in the Cu doped Sr2 YRu O6 were found. Thereupon more and more perovskite related research springed up.Through high temperature and high pressure synthesis method, several perovskite structure materials were successfully obtained for the first time, including single perovskite SrFe_0.5Cr_0.5O₃, B-site ordered double perovskite Pb₂FeOsO₆ and A-site ordered perovskite CaCu₃Cu₂Ir₂O₁₂. And their crystal structure, electronic transport, magnetism and thermal physical properties were studied.For single perovskite SrFe_0.5Cr_0.5O₃, through two different synthesis methods, high-quality polycrystalline samples were obtained. And their crystal structures belonged to the cubic crystal system, space group was Pm-3m. B-site cations were disordered, Fe and Cr ions randomly occupied the B sites. But in physical property characterization, SrFe_0.5Cr_0.5O₃ samples obtained by different methods were different. One was metal with spin glass behavior, the other was magnetic insulator with a high TC.In double perovskite Pb₂FeOsO₆, the structure refinement using X-ray diffraction data revealed its space group was I4/m?tetragonal?, B-site cations were ordered. The BVS indicated the valence approximately obeyed Pb2+2Fe3+Os5+O6, which was proved by the XAS. And its resistivity showed semiconductor behavior. Photovoltage spectrum measurement results showed that the energy gap was 1.77 e V. Magnetism showed ferimagnetic behavior.Structure refinement using X-ray diffraction data revealed CaCu₃Cu₂Ir₂O₁₂ was A-site ordered perovskite with disordered B-sites, its space group was Im-3,. The XAS showed valence distribution was Ca Cu2+3Cu3+2Ir5+2O12. It was a Pauli paramagnetic metal.