Rutile TiO2 microwave dielectric ceramics prepared via cold sintering assisted two step sintering

In this work, a sintering route named cold sintering assisted two step sintering process (CSP-TS) is presented to prepare rutile TiO2 ceramics with submicron grain sizes. Cold sintering process at 300 ?C with tetrabutyl titanate and water as the liquid phase yields a ?green body? with a relatively high density of -80 %, and finally dense (98.5?99.8 %) rutile TiO2 ceramics with grain sizes of -600 nm can be obtained in the second sintering process at 950-1000 ?C. The microstructural analysis with SEM and TEM indicates that the CSP-TS samples sintered at 950 ?C have an obvious phenomenon of recrystallization, accompanying by a decrease of amorphous phases and a formation of clear grain boundaries. Besides, the rutile TiO2 ceramics prepared by CSP-TS possess excellent microwave dielectric properties with relative permittivity of 92.0?98.4 and Q x f values of 27,800-31,900 GHz. Therefore, it is feasible to utilize CSP-TS to prepare ceramics with small grain sizes at low sintering temperatures.