Abstract
As one of the chemical powder fabrication methods, the powder preparation method by using oxalate has the following advantages; (1) easy to control the chemical stoichiometry, (2) easy to fabricate homogeneous and fine particles, and (3) easy to be thermaly decomposed at low temperature. In the present study, the initial morphology and size distribution of the powder were controlled and the homogeniaty was improved. By carefully controlling the pH with NH4OH, the Bi(Pb)-Sr-Ca-Cu-O superconducting powders were prepared and investigated for their properties. The microstructures and the superconducting properties of the pelletized samples were investigated. Also, the microstructures and electrical properties of the samples prepared by tape casting method were investigated. The fabricated powders were spherical with less than 400 nm, but most of them were agglomerated to be 1~3 ${\mu}{\textrm}{m}$ in size. The critical temperature of the pelletized sample annealed at 84$0^{\circ}C$ for 72 hours in air was 110K. And the critical currents of annealed samples in air prepared by tape casting process for 24 hours and 72 hours were 0.6 A (Jc=600A/$\textrm{cm}^2$) and 1.9A (Jc=1, 900A/$\textrm{cm}^2$) respectively.
반응성이 좋은 미분말의 고온 초전도상을 얻고자 액상 합성법 중의 하나인 옥살산염법을 이용하였다. 본 방법을 사용하여 합성 분체의 초기 형상과 입도를 제어하였고, 개선된 균일성을 가진 Bi(Pb)-Sr-Ca-Cu-O 초전도 분말을 제조할 수 있었다. 합성된 산화물 초전도체 분말의 특성 및 pellct으로 성형후 열처리한 시편의 미세구조와 전기적특성을 조사하였다. 또한, Tape casting법에 의해 후막을 제작하여 미세구조와 전기적 특성을 관찰하였다. 합성된 분말의 입자 크기는 100~300nm 이하의 구형이었으나 대부분이 1~3 ${\mu}{\textrm}{m}$ 크기로 응집되어 있었다. 84$0^{\circ}C$로 72시간 동안 열처리한 괴상 시편의 임계저항온도는 110K였으며, 열처리한 후막의 임계전류는 각각 0.6A, 1.9A였다.