การคำนวณและการวัดสมบัติเทอร์มออิเล็กทริกของสารระบบ BSCCO

Abstract

Electronic structure of BSCCO system was calculated by DV-Xa method based on FORTRAN and MATHEMATICA programs. The Bi₈Sr₈CuO₁₄, Bi₈Sr₂Cu₈CaO₁₈and Bi₈Sr₂Cu₉Ca₂O₂₂cluster models were designed for Bi-2201, Bi-2212 and Bi-2223, respectively.The calculation consisted of energy level, density of state and contour map. The amorphous of Bi-Sr-Ca-Cu-O was synthesized by melt quenched method. Crystallography wassynthesized by X-ray diffractometer(XRD). Electrical resistivity( ) and Seebeck coefficient (S) were measured by ZEM-1.Thermal diffusivity (D) was measured by laser flash method.The results showed that cluster models were symmetry at 7(D2h) level. Eigenvectors were ag, b1g, b2g, b3g, au, b1u, b2u and b3u. Theenergy gap of Bi-2201, Bi-2212 andBi-2223 cluster models were 0.962, 1.10 and2.06 eV, respectively. The synthesized BSCCO contained 3 phases, Bi₂Sr₂CuO₆(Bi-2201), Bi₂Sr₂CaCu₂O₈ (Bi-2212) andBi₂Sr₂Ca₂Cu₃O₁₀ (Bi-2223). This was confirmed by XRD results. The BSCCO system showed lowthermoelectric properties.