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Hafnium-substituted zirconium tin titanate dielectric ceramics with the general formula ( with x = 0, 0.05, 0.2, 0.4, 0.6, 0.8 and 1.0 have been synthesized by the conventional solid state ceramic route. The phase purity, crystal structure and microstructure of these compositions have been examined by powder x-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis shows that ( undergoes a structural change as a function of x for x>0.6. The microwave dielectric resonator properties the dielectric constant , quality factor (Q) and temperature coefficient of the resonant frequency have been measured. The value is found to decrease with increasing Hf content. The elastic properties of these materials have been investigated by measuring their longitudinal and shear elastic modulii. Measurements of the temperature variation of the elastic modulii indicate that there might be a diffuse phase transformation in these materials above room temperature.

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The Ba2- x Sr x Ti9O20 ceramics with different values of x ranging from 0–2 have been prepared by the solid state reaction route. The longitudinal and transverse elastic constants of these samples have been measured by the ultrasonic Pulse Echo Overlap method. The composition and temperature dependence of the elastic constants have been investigated. The low frequency dielectric constant of the samples have been measured. The frequency and temperature dependence of dielectric constant have been studied and the results are interpreted in terms of the composition dependent microstructural phase transformation taking place in the system.