The dielectric properties and phase transition of Ho2O3 modified barium strontium titanate ceramics for capacitor applications

The microstructure and dielectric properties of Ho2O3 doped (Ba0.75Sr0.25)TiO3 ceramics prepared by conventional solid state method were studied using XRD, SEM, EDS and LCR measure system. It is found that the Ho3+ ions initially substitute the host ions of (Ba0.75Sr0.25)TiO3 perovskite lattice and then participate in the formation of secondary phase when Ho2O3 content reaches up to 9 wt%. The average grain size of (Ba0.75Sr0.25)TiO3 ceramics decreases with the increasing Ho2O3 concentration. The Curie temperature and the orthorhombic?tetragonal phase transformation temperature decrease with the increase of Ho2O3 content. The relative dielectric constant maximum as well as the relative dielectric constant at room temperature is enhanced and then restrained as the Ho2O3 content increases. The diffuseness of ferroelectric-paraelectric phase transition resulting from the composition fluctuation and the grain boundary effect is exacerbated significantly as the Ho2O3 addition content increases, which improves the temperature stability of the relative dielectric constant in (Ba0.75Sr0.25)TiO3 system.