Superconducting transitions of LuBa2Cu3O7-z heated under various atmospheres

초록

The influence of quenching temperature, heating atmosphere and annealing time on superconducting characteristics has been studied for LuBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-z</inf> compound which has been recently synthesized in a nearly phase-pure form. Resistivity measurements for the as-prepared sample heated at 300 °C in oxygen and subsequently quenched into liquid nitrogen revealed that there is no significant change in T<inf>c</inf>. On the other hand, T<inf>c</inf> of the sample slightly increased when the sample was heated at 300 °C either in air or in N<inf>2</inf> atmosphere. It was also found that T<inf>c</inf> of the sample decreased when the annealing temperature in N<inf>2</inf> atmosphere increased above 400 °C. The experimental results indicated that the as-prepared sample is under overdoped state. The enhanced superconducting transition observed in the samples after heating at 300 °C in air or N<inf>2</inf> atmosphere was discussed in conjunction with a slight removal of oxygen and ordering of oxygen atoms in the as-prepared sample.

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