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

Abstract

Calcium hafnium titanate, Ca(HfxTi1-x)O3 (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 Hf4+ ions over Ti4+, 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).