Large static dielectric constant in the high-temperature phase of polycrystalline YBa2Cu3Ox.

A large and strongly temperature-dependent static dielectric constant kappa is found in the high-temperature (T>900 /sup 0/C) phase of YBa/sub 2/Cu/sub 3/O/sub x/. Values of kappa from approx.30 at 4.3 K to approx.700 at 290 K have been measured in samples quenched from 950 /sup 0/. Some consequences of the ferroelectriclike polarizability in the phase which precedes the metallic/superconducting phase are noted.