Evidence of Sr-Deficiency in Bi₂Sr_2-αCa₁Cu₂O₈ and Preparation of Stoichiometric Semiconducting Bi₂Sr₂Ca₁Cu₂O₈

Abstract

When samples with the starting composition of Bi:Sr:Ca:Cu=2:2:1:2 were heat-treated under the oxygen partial pressure range from 1 to 0.0001 atm at 820°C, at least three different multiphase regions with the following component phases appeared: Bi 2 Sr 2 Cu 1 O y +Sr-rich Bi-Sr-Ca-Cu-O+Sr-deficient Bi 2 Sr 2-α Ca 1 Cu 2 O x , stoichiometric Bi 2 Sr 2 Ca 1 Cu 2 O 8 , and Bi 2 Sr 2 Ca 1 O 6 +Cu 2 O. The amount of Sr-deficiency in the Bi 2 Sr 2-α Ca 1 Cu 2 O 8 homogenized sample with the stoichiometric composition of Bi 2 Sr 2 Ca 1 Cu 2 O 8 exhibited semiconductivity.