Contribution of structure to temperature dependence of resonant frequency in the (1-x)La(Zn1/2Ti1/2)O3•xATiO3 (A = Ca, Sr) system

The crystal structure and microwave dielectric properties of the (1 - x)La(Zn1/2Ti1/2)O-3. xSrTiO(3) and (1 - x)La(Zn1/2Ti1/2)O-3. xCaTiO(3) system were investigated. X-ray powder diffraction showed that cation ordering disappeared at x > 0.3 for both systems. However, infrared spectra demonstrated that short-range cation ordering could exist at x = 0.4. Permittivity and the temperature coefficient of the resonant frequency (tau (f)) of both systems exhibited nonmonotonic variations with composition. Both systems exhibited a tau (f) of zero at the same composition of x = 0.5 although the tau (f) of SrTiO3 was about two times larger than that of CaTiO3. The behavior of the permittivity and tau (f) were described by the tilting of oxygen octahedra and cation ordering. The relation between I, and cation ordering of La(Zn1/2Ti1/2)O-3 was discussed in conjunction with the experimental results on metal halides, It is suggested that cation ordering induced a negative tau (f) and suppressed the increase of permittivity for compositions between x = 0 to x = 0.5 for (1 - x)La(Zn1/2Ti1/2)O-3. xSrTiO(3) and (1 - x)La(Zn1/2Ti1/2)O-3. xCaTiO(3) systems.