Enhanced quality factor of CaMo1 − xTexO4 ceramics by Te6+ substitution

Microwave dielectric properties of CaMo 1– x Te x O 4 (0.01 ≤ x ≤ 0.05) ceramics were investigated based on the crystal structure characteristics. For the specimens sintered at 900–985 °C for 2 h, a single phase of scheelite structure was confirmed up to x = 0.03, and then secondary phases were observed for further substitution. With an increase in Te 6+ content, the quality factor ( Qf ) of the sintered specimens increased up to x = 0.03 ( Qf = 185,500 GHz) and then decreased. The amelioration in the Qf up to x = 0.03 is due to the increase in the B-site bond valence of ABO 4 ; however, the degradation of the Qf above x = 0.03 could be attributed to the formation of secondary phases. With an increase in Te 6+ content, the dielectric constant ( K ) of the specimens increased from K = 10.42 to K = 10.78 due to the higher polarizability of Te 6+ (3.7 Å 3 ) than that of Mo 6+ (3.28 Å 3 ). As the Te 6+ content increased, the temperature coefficient of resonant frequency ( TCF ) decreased with an increase in oxygen bond valence. Excellent microwave dielectric properties ( Qf = 185,500 GHz, K = 10.62, TCF = -36.53 ppm/°C) were obtained for the CaMo 0.97 Te 0.03 O 4 ceramics which could be applicable to various microwave communication systems.