Phase Stability of bulk (R0.8Ca0.2)Ba2Cu3Oz (R = Lu and Y) Compounds

초록

Polycrystalline samples of (R0.8Ca0.2)Ba2Cu3O7-z (R = Lu and Y) were synthesized by a solid-state reaction route, and the phase stabilities were examined by heating at temperatures between 800 ℃ and 900 ℃ in various atmospheres. A comparative analyses of the x-ray diffraction data of the (Lu0.8Ca0.2)Ba2Cu3O7-z and (Y0.8Ca0.2)Ba2Cu3O7-z compounds showed that the 123 phase of both compounds is stable under heating in air and O2 of 1 atm. However, contrary to the (Y0.8Ca0.2)Ba2Cu3O7-z compound, the (Lu0.8Ca0.2)Ba2Cu3Oz compound was found to become unstable when heated in the low oxygen partial pressure below about 8 % O2 in N2, Considering the instability of parent LuBa2Cu3Oz compound, this result suggests that the phase stability of Lu-based 123 compounds is sensitive to both the composition and the oxygen partial pressure.

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