Structures and microwave dielectric behavior of Sr0.1Ca0.9TiO3–Bi0.1Na0.1Li0.4Sm0.4TiO3 ceramic system
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Microwave dielectric ceramics with xSr0.1Ca0.9TiO3–(1−x)Bi0.1Na0.1Li0.4Sm0.4TiO3 (xSCT–BNLST) compositions were prepared through the conventional oxide-state reaction. X-ray diffraction results showed that the symmetry in xSCT–BNLST system were improved with the increase of x. Based on the calculation results, the deviation of observed dielectric polarizabilities from theoretical values could be ascribed to the increase of A-site ionic polarizability and B-site bond valence. The decreased temperature coefficient of resonant frequency, τf, was dependent on the B-site bond valence in the tilted region. With the increase of temperature, the samples changed their main conductive carrier, from first ionization of oxygen vacancies to second ionization of oxygen vacancies. Optimum microwave dielectric properties were achieved, for 0.09SCT–BNLST ceramic with relative permittivity, εr = 111, quality factor, Q × f = 3819 GHz and τf ~ 0 ppm/°C. The system has the potential for use in dielectrically loaded antennas and C0G high-frequency filter applications.
KeywordsIonic polarizability B-site bond valence Impedance spectroscopy Oxygen vacancies
Financial support of the Enhanced Project of Basic Capability for Middle Young Teachers (Grant No. 2017KY0209) is gratefully acknowledged by the authors.