Sintering behavior and microwave dielectric properties of MgZrTa2O8 ceramics with fluoride addition

MgZrTa2O8 ceramics with CaF2 addition were synthesized by solid-state reaction, and the effects of CaF2 addition on sintering behavior and microwave dielectric properties were investigated. The densification of MgZrTa2O8 ceramics could be effectively accelerated with CaF2 addition and the sintering temperature of CaF2-doped MgZrTa2O8 ceramics was lowered from 1475 degrees C to 1375 degrees C due to liquid phase effect. The phase composition of MgZrTa2O8 ceramics with CaF2 addition varied from single phase to three phases because of the reaction between MgZrTa2O8 and CaF2. Well-developed microstructure was observed with 0.5 wt% CaF2 addition owing to the single phase. The microwave dielectric properties presented a significant dependence on extrinsic effects. The dielectric constant (epsilon(r)) of CaF2-doped MgZrTa2O8 ceramics had no significant difference for all levels of CaF2 addition. The quality factors Q x f were strongly affected by the content of CaF2 owing to the density, grain size and phase composition. The temperature coefficients of resonant frequency (tau(f)) were correlated with the dielectric constant, which could be optimized to -2.86 ppm/degrees C with CaF2 addition. In this work, the MgZrTa2O8 ceramics could be optimized to the temperature-stable dielectric material for microwave application. (C) 2018 Elsevier B.V. All rights reserved.