Development of low cost (Sr,Ca)(3)Al2O6 dielectrics for Bi2Sr2CaCu2O8+delta applications

Aspects of the development of low-cost (Sr,Ca)(3)Al2O6 dielectrics for Bi2S r2CaCu2O8+delta superconductor applications were investigated. A tie-line p hase equilibrium relationship between Bi2Sr2CaCu2O8+delta and Sr2CaAl2O6 co mpositions was observed at 860 degreesC. When the Bi-2212 and (Sr,Ca)(3)Al2 O6 solid-solution compositions were changed slightly, the tie-line relation ship was not preserved, and a new phase was observed to form with compositi on similar to BiSr1.5Ca0.5Al2Ox. Composites of (0 to 24) volume fraction % Sr2CaAl2O6 + Bi2Sr2CaCu2O8+delta equilibrated at 860 degreesC slightly redu ced the T-c (by 2 g to 4 K) and superconducting volume percentage of the 22 12 phase. The dielectric properties of (Sr = 1.0 to 2.5) members of solid-s olution (Sr,Ca)(3)Al2O6 were measured at 77 K and 297 K in the range of (10 to 11) GHz for cylindrical samples using resonant system methods. The diel ectric constant epsilon (r) varied from 9.7 to 13.2, and the loss tangent t an delta was from 3 x 10(-4) to 8 x 10(-4).