Hot isostatic press sintering and dielectric properties of SrTaO2N ceramics

SrTaO2N prepared by a citrate route was capsule hot isostatic press sintered at 196 MPa for 3 h at 1200, 1400 and 1600 °C. Densification over 80% was attained for all the sintered bodies with partial reduction, which was observed as a change of color from brown to dark gray. Exaggerated grain growth was observed with some amount of open pore for the product sintered at 1400 °C. The sample was successfully returned to the brown insulator color after annealing in ammonia flow at 1000 °C. The resultant SrTaO2N ceramics exhibited a considerably high relative dielectric permittivity of 7.8×103 at 102 Hz.