Microwave dielectric properties of Re3Ga5O12 (Re: Nd, Sm, Eu, Dy and Yb) ceramics and effect of TiO2 on the microwave dielectric properties of Sm3Ga5O12 ceramics

Re3Ga5O12 (Re: Nd, Sm, Eu, Dy and Yb) garnet ceramics sintered at 1350–1500 °C had a high quality factor (Q × f) ranging from 40,000 to 192,173 GHz and a low dielectric constant (ɛr) of between 11.5 and 12.5. They also exhibited a relatively stable temperature coefficient of resonant frequency (τf) in the range of −33.7 to −12.4 ppm/°C. In order to tailor the τf value, TiO2 was added to the Sm3Ga5O12 ceramics, which exhibited good microwave dielectric properties. The relative density and grain size increased with addition of TiO2, resulting in the enhancement of Q × f value. The τf increased with the addition of TiO2. Excellent microwave dielectric properties of ɛr = 12.4, Q × f = 240,000 GHz and τf = −16.1 ppm/°C were obtained from the Sm3Ga5O12 ceramics sintered at 1450 °C for 6 h with 1.0 mol% TiO2. Therefore, Re3Ga5O12 ceramics, especially TiO2-added Sm3Ga5O12 ceramics are good candidates for advanced substrate materials in microwave integrated circuits (MICs) applications.