EFFECT OF HIGH-TEMPERATURE, HIGH-OXYGEN-FUGACITY ANNEALING ON THE STABILITY OF THE (BI,PB)(2)SR2CA2CU3O10+ -DELTA-TYPE COMPOUND/

The stability of the (Bi,Pb)(2)Sr2Ca2Cu3O10+/-delta-type compound has been evaluated under conditions of elevated temperature (500 degrees-8 60 degrees C) and elevated oxygen fugacity (i.e., in O-2/Ar gas mixtur es containing less than or equal to 20% 0(2) at total pressures of les s than or equal to 207 MPa). At sufficiently high oxygen fugacities an d temperatures, the (Bi,Pb)(2)Sr2Ca2Cu3O10+/-delta-type compound trans formed into a mixture of a strontium-rich (Bi,Pb)(1)-(Sr,Ca,Cu)(2)O-y- type compound, a calcium-rich (Bi,Pb)(1)-(Sr,Ca,Cu)(2)O-y-type compoun d, CuO, and a small amount of (Sr,Ca)O. The decomposition of the (Bi,P b)(2)Sr2Ca2-Cu3O10+/-delta-type compound was accompanied by a 2%-3% we ight gain, which was consistent with anoxidation reaction. The conditi ons of oxygen fugacity and temperature leading to decomposition, and t he resulting decomposition products, are compared for the (Bi,Pb)(2)Sr 2Ca2Cu3O10+/-delta-type and Bi2Sr2Ca1Cu2O8+/-psi-type compounds.