Structural investigation and improvement of microwave dielectric properties in Ca(HfxTi1-x)O3 ceramics

Abstract Calcium hafnium titanate, Ca(Hf x Ti 1-x )O 3 (CHT) was prepared using the conventional solid state reaction route. The X-ray diffraction patterns were used for analyzing the phase compositions. The XRD patterns revealed the arrangement of a single phase perovskite structure and therefore the structure is transformed from non-centrosymmetric orthorhombic (Pbnm) to centrosymmetric cubic (Pm-3m) at 0.4 ≤ x. Lattice parameter, crystallite size, densities and porosity were calculated. The SEM morphology of CHT at various hafnium (x), which is comprises of round-rod shaped grains with small pores microstructure. The substitution of Hf 4+ ions over Ti 4+ , the microwave dielectric constant ( ε r ) decreases from 145 to 52, while the quality factor (Qxf) increases from 8105 to 24305 GHz and temperature coefficient of resonant frequency tuned towards zero τ f ∼ 4.5 ppm °C −1 . Good combination of microwave dielectric material properties was accomplished for the composition x = 0.8 (at 3 GHz).