EFFECT OF GA-ADDITION ON THE GLASS-FORMING ABILITY AND SUPERCONDUCTING PROPERTIES OF BI-SR-CA-CU-O SYSTEM

The effect of the addition of Ga2O3, a conditional glass former, on th e glass-forming ability and superconducting properties of samples with Bi2-xGaxSr2Ca2Cu3Oy (x=0-1.5) compositions has been investigated. The quantity T-x-T-g increases from 54 to 68 K, indicating an improvement in the glass forming ability of the samples, where T-g and T-x are gl ass transition and crystallization temperatures, respectively. The sup erconducting properties deteriorate due to the migration of Ga ions in to the 2212 phase: the superconducting critical temperature of the 221 2 phase decreases from 85 K for Ga-free sample to 72 K for the sample with x=0.5, and the sample with x=1.5 shows semiconducting properties. The c-axis length of the 2212 phase decreases, from 3.081 nm for Ga-f ree sample to 3.074 nm for the sample with x=0.5, but a- and b-axis le ngths remain constant, A new Ga-compound formed in Ga-added samples wa s identified to be GaSr0.55Ca1.05Cu0.5Ox. Superconducting phases of th e Ga-based system are not formed even in Ga-rich samples.