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.