TUNABILITY OF THE DIELECTRIC-CONSTANT OF BA0.1SR0.9TIO3 CERAMICS IN THE PARAELECTRIC STATE

Ba1-xSrxTiO3 (x = 0.9) ferroelectric ceramics were prepared successful ly using a new wet technique and their structure and dielectric proper ties compared with those synthesized by the solid-state reaction metho d, The voltage dependence of the dielectric constant in the paraelectr ic phase was examined. It was found that the dielectric constants of t hese materials, prepared by both methods, exhibit large changes with a pplied voltage in the paraelectric phase. Tunability (the percentage c hange of the dielectric constant from its zero-bias value in the prese nce of a dc-biasing electric field) was observed to exceed 30% at only 1.7 kV/cm at 77 K in the samples prepared by the solid-state reaction method. The tunability was found to decrease dramatically as the oper ating temperatures increased above the Curie point. These observations are interpreted in light of an existing phenomenological theory. The dependence of the dielectric constant in the paraelectric state upon a dc-biasing electric field is also demonstrated as a potential method for the characterization of dielectric nonuniformities in ferroelectri c ceramics.