Effect of MgO and Nb₂O₅ co-doping on the microwave dielectric properties of Y₂Ti₂O₇ ceramics

This study investigated the effects of MgO and Nb₂O₅ co-doping on the microwave dielectric properties of Y₂Ti₂O₇ ceramics with a medium dielectric constant. Substituting (Mg_1/3Nb_2/3)⁴⁺ for Ti⁴⁺ in Y₂Ti₂O₇ ceramics effectively enhanced the quality factor Qf. The interrelationship among the crystalline structure, microstructure, and microwave properties of Y₂(Ti_1-x(Nb_2/3Mg_1/3)_x)₂O₇ (0 ≤ x ≤ 0.15) sintered at 1500 °C with different holding times were examined using XRD, SEM, TEM, XPS, Raman, and network analyzer. The research findings indicate that all samples exhibited a single cubic pyrochlore phase without a second phase. Moreover, the densification temperature increased with an increase in (Mg_1/3Nb_2/3)⁴⁺ content, and the relative density could be increased by increasing the sintering dwell time. The sample with x = 0.025 demonstrated an optimal densification temperature of 1500 °C. TEM/SAED pattern analysis revealed the existence of a “superlattice” due to the occurrence of a 1:2 cation ordering structure at high temperatures. As the dwell time was extended from 4 h to 12 h, the quality factor Qf increased from 10,830 GHz to 46,068 GHz. The sample with x = 0.025 sintered at 1500 °C for 12 h exhibited the best microwave dielectric properties (permittivity(ε_r) = 62.5, Qf = 46,068 GHz, and the temperature coefficient of frequency (TCF) = 290.8 ppm/°C).