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Sintering and Dielectric Properties of SrTiO3-based Ceramics Juan Li1,2, Dengren Jin1,2, Lixin Zhou1,2 and Jinrong Cheng1 1 School of Materials Science and Engineering, Shanghai University, Shanghai, 200072, People’s Republic of China. 2 State Key Lab of Silicon Materials, Zhejiang University, Hangzhou, 310027, People’s Republic of China. ABSTRACT High dielectric tunability, low dielectric loss tangent and appropriate level of dielectric constant are the basic requirements for applications as electrically tunable dielectric microwave devices. In our experiments, the SrTiO3 green compacts made of the powder mixtures with various particle sizes were infiltrated with a BaTiO3 precursor solution and sintered at different temperatures between 1280 and 1350 ºC for 2 hours and 1350 ºC for 6 hours. The sintering, microstructural and dielectric properties were investigated. Results showed that the relative density of SrTiO3 ceramics could reached 93% when sintered at 1280 ºC for 2 hours. When sintered for 6 hours at 1350 °C, the room temperature dielectric constant of SrTiO3 reaches 900 at a frequency of 1MHz. It has only weak temperature dependence between 100 and 500K. The reason of the low sintering temperature for the dense SrTiO3 ceramics and the effects of sintering scheme on the dielectric properties from 100 K to 500 K are discussed in this paper. INTRODUCTION The ferroelectric materials, whose dielectric constants can be controlled by an applied electric field, have been proved to be great promising materials for microwave applications as tunable devices [1, 2]. Currently, the ferroelectric materials considered as a promising candidate for practical tunable microwave applications mainly are the Ba1-xSrxTiO3 (BST) solid solution system for applications at room temperature [3] and strontium titanate (SrTiO3; ST) at cryogenic temperatures [4-6]. As an incipient ferroelectric, SrTiO3 stays paraelectric down to 0 K and its dielectric constant strongly increases with decreasing the temperature and has long been investigated because of its high dielectric permittivity and low loss factor at microwave frequencies (below 10-3)[7-9]. Dense ST ceramics is hard to obtain when a convention solid-state reaction method is used. Usually a sintering temperature as high as 1450 °C is required to achieve a relative density larger than 95% [10, 11]. On the other hand, low sintering temperature (< 1300 ºC) is also required to match with alumina substrate in fabrication of thick film devices [12]. In this paper, we fabricated dense SrTiO3 ceramics at low sintering temperatures with the help of a sol-filtered technique and by tuning the powder’s particle size distribution, and their sintering behaviors, microstructures and dielectric properties were investigated. EXPERIMENTAL The SrTiO3 powders were synthesize by using a solid-state reaction method. SrCO3 and TiO2 used as the raw materials were weighed out according to stoichiometric proportion of

SrTiO3 and calcined either at 1100°C or at 1200°C for 2 hours. The ST powders calcined at