Design of dielectric substrates for high T-c superconductor films

Investigations on the design and engineering of candidate substrate materials suitable for high T-c superconductor thin film deposition and applications have yielded several exciting new hosts such as Ba(Mg1/3Ta2/3)O-3, Sr(Al1/2Ta1/2)O-3, and ST(Al1/2Nb1/2)O-3 Dielectric properties, thermal expansion coefficients, melting temperatures and growth feasibility were tested for a wide range of substrate materials and solid solutions. These complex perovskite crystals and their associated solid solutions provide new options for ultra low loss, low permittivity substrates with close structural and thermal matching to the YBa2Cu3O7-delta. Several new materials have been tested for high T-c superconductor film depositions. A laser heated pedestal growth system has been used as an essential tool in producing single crystals for testing. Development on the predictive capability of the dielectric constant of ionic solids, by improving Shannon's approach, will also be discussed in this paper.