Effects of complex substitution of La and Nd for Bi on the microwave dielectric properties of BiNbO4 ceramics

La2O3 and Nd2O3 were used to substitute Bi2O3 and the effects of complex substitution on the sintering behavior and the microwave dielectric properties of BiNbO4 ceramics were studied. With 0.5 wt.% CuO–V2O5 mixtures addition, all of the Bi1−x(La0.38Nd0.62)xNbO4 ceramics could be densified below 920 °C. The triclinic phases are identified in Bi1−x(La0.38Nd0.62)xNbO4 ceramics with x=0.01 sintered at 820 °C and the triclinic intensities increase with increasing the x value and sintering temperature. The saturated bulk density slightly decreases from 7.17 to 7.13 g/cm3 and the εr value from 44.24 to 42.76 with increasing x from 0 to 0.07 for Bi1−x(La0.38Nd0.62)xNbO4 ceramics. The saturated Q×f value is between 10,300 and 12,400 GHz depending on the x value. The τf values of dense Bi1−x(La0.38Nd0.62)xNbO4 ceramics decrease from 28.32 to 12.79 ppm/°C with x varying from 0 to 0.01 and remain almost unchanged with further increasing x.