MICROWAVE DIELECTRIC PROPERTIES OF Ba0.75Sr0.25 (NdxBi1-x)2Ti4O12 SOLID SOLUTION

Long Mingzhu, ZHuang WENDONG, Tang Bin, Yu Shengquan, Zhou Xiaohua, Zhang Shuren
2011 Ceramics-Silikáty  
This work investigated the influences of Bi content on the phase structure, phase composition, microstructure and microwave properties of tungstenbronze-type like Ba0.75Sr0.25(NdxBi1-x)2Ti4O12 ceramics. XRD patterns showed that the main crystal phase of the ceramics with different Bi content (0.75 ≤ x ≤ 0.9) sintered at 1250°C to 1400°C for 3 h was BaNd2Ti4O12 with small amount of second phase Ba2Ti9O20. SEM photographs suggest that Bi could work as sintering aids promoting the densification
more » ... grain growth. In the case of the ratio of Nd and Bi (x : (1-x)) is 3:1 namely x is 0.75(B13), this ceramic shows optimum dielectric properties with a high dielectric constant (ε) of 118.5, a quality factor (Q × f) of 4907 (f = 2.8 GHz), and a temperature coefficient of resonant frequency tf = –1.3 ppm/°C. As the addition of Bi increased from 0.1 to 0.25, the value of ε markedly increased, the value of Q × f and tf decreased with a tf value finally approaching to zero.
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