Effect of A-site cobalt doping on the structural, micro-structural and dielectric properties of (Ba1-xCox)(Ti0.95Zr0.05)O3 lead-free ceramics

Abstract

Cobalt-doped barium zirconate titanate ceramics with (Ba1-xCox)(Ti0.95Zr0.05)O3 with (x = 0, 2.5, 5, 7.5 and 10 %) were synthesized by sol-gel process. The effects of Ba/Co ratio on structural, micro-structure properties and dielectric response were investigated by varying the value of x. X-ray diffraction analysis and the Rietveld refinement method revealed that the ceramics have a single phase with a tetragonal structure of the P4mm space group. The scanning electron microscope (SEM) was used to examine the texture, morphology and microstructure of the (Ba1-xCox)(Ti0.95Zr0.05)O3 ceramics. The analysis showed a decrease in average grain size as the concentration of Co2+ ions in the crystal structure increased. A study of the impedance spectroscopy of the dielectric measurements was carried out in a temperature range from room temperature to 200 °C, and revealed that the ferroelectric to paraelectric phase transition temperature decreases proportionally with increasing cobalt concentration, confirming the incorporation of Co2+ and highlighting its influence on the Curie temperature (Tc), the value of the permittivity (εr) and dielectric losses (tanδ). The Curie-Weiss law was used to study the nature of the transition, revealing that diffusivity increases in correlation with the Co2+ ion concentration.