Bi-계 산화물 고온초전도체 (2212상)의 Ca 위치에 Na 대치 효과 = Effect of Na Substitution for the Ca site in the Bi(2212 phase) high-Tc Superconductors

다국어 초록 (Multilingual Abstract)

The samples of Bi₂Sr₂Ca₁-x Nax Cu₂O8+y with various carrier concentration were synthesized by substituting Na for Ca ion. The superconducting properties, hall coefficients and X-ray powder diffraction were measured the samples. Single phase samples were obtained for 0≤x <0.3 of Bi₂Sr₂Ca₁-x Nax Cu₂O8+y. In the single phase, the critical temperature Tc and carrier concentration increase with the increase of Na concentration pass through a maximum and then decrease. In the range of x ≥0.7 to the Na doped samples, howerever, we observed the metal-semiconductor transition. The c-axis seemed to decrease and a, and b-axes increase with increasing Na concentration in the single phase. Decreasing of c-axis while increasing x is due to the smaller size of Na+¹ions to the Ca+²ions. In the range of x > 0.3, however, the trend becomes ambiguous due to the inclusion of the 10 K phase and impurity phase.