Effects of Al_2O_3 additive on sintering behavior and microwave dielectric properties of ZnTa_2O_6 ceramics

摘要

ZnTa_2O_6 ceramics with various amount of Al_2O_3 additive were synthesized by a conventional mixed-oxide route. The grain growth of ZnTa_2O_6 ceramics was accelerated with Al_2O_3 additive. However, excessive addition (＞1.0 wt%) of Al_2O_3 leaded to abnormal grain growth. With Al_2O_3 addition, the Al_2O_3 additive did not solubilized into ZnTa_2O_6 structure but resulted in forming the second phase. The Al_2O_3 addition resulted in the lower sintering temperature of ZnTa_2O_6 ceramics and improved microwave dielectric properties. The dielectric constant (ε_r) of the samples did not change much and ranged from 32.41 to 34.33 with different amount of Al_2O_3 addition. The optimized quality factor (Q×f) was higher than 70,000 GHz as a result of the denser ceramics. The temperature coefficient of resonant frequency (τ_f) of the doped ZnTa_2O_6 ceramics could be optimized to near-zero.