Influence of CeO2 on microstructure and microwave dielectric properties of Na1/2Sm1/2TiO3 ceramics
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Crystal structures and microwave dielectric properties of wt% CeO2-added Na1/2Sm1/2TiO3 (NST) ceramics were investigated systematically (x = 0.0, 0.3, 0.6, 0.9 and 1.2). Samples with CeO2 content ≤1.2 wt% were crystallized as single phase of orthorhombic perovskite structures. When Ce4+ initially entered into the A-site of perovskite structure, uniform grain growth was observed and the dielectric constant increased, but then as Ce4+ began to enter into the B-site of the perovskite structure, abnormal grains appeared and the ε r value reduced. The Q × f value was firstly enhanced to its maxim value of 9640 GHz due to the improvement of density and elimination of pores as Ce4+ content was in the range of 0.0–0.6 wt%, then sharply decreased. The temperature coefficient of resonant frequency (τ f ) slightly decreased from 199.7 to 185.1 ppm/°C. Typically, specimens sintered in air at 1425 °C for 2 h exhibited excellent microwave dielectric properties of ε r = 103.01, Q × f = 9640 GHz and τ f = 192.8 ppm/°C. The relationships between microwave properties and crystal structures were also discussed in this paper.
KeywordsDielectric Constant Perovskite CeO2 Resonant Frequency Apparent Density
This work is supported by National Natural Science Funds of China (Grant No. 51402039).
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