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Abstract: 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 192,173GHz and a low dielectric constant (ɛ r) of between 11.5 and 12.5. They also exhibited a relatively stable temperature coefficient of resonant frequency (τ f ) in the range of −33.7 to −12.4ppm/°C. In order to tailor the τ f 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 τ f increased with the addition of TiO2. Excellent microwave dielectric properties of ɛ r =12.4, Q × f =240,000GHz and τ f =−16.1ppm/°C were obtained from the Sm3Ga5O12 ceramics sintered at 1450°C for 6h with 1.0mol% TiO2. Therefore, Re3Ga5O12 ceramics, especially TiO2-added Sm3Ga5O12 ceramics are good candidates for advanced substrate materials in microwave integrated circuits (MICs) applications. [Copyright &y& Elsevier]