Microstructural and Dielectrical Characterization of Ho Doped BaTiO3 Ceramics

Abstract

The Ho doped BaTiO3 ceramics, with different Ho2O3 content, ranging from 0.01 to 1.0 wt % Ho, were investigated regarding their microstructural and dielectric characteristics. Doped BaTiO₃ were prepared using conventional solid state reaction and sintered at 1380°C for four hours. SEM analysis of Ho/BaTiO₃ doped ceramics showed that the low doped samples exhibit mainly fairly uniform and homogeneous microstructure with the grain size ranged from 20- 40 µm. In the samples with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2-10 µm. Measurements of dielectric properties were carried out as a function of temperature up to 180 °C at different frequencies. The samples doped with 0.01wt % of Ho, exhibit the high value of dielectric permittivity (ε_r = 2160) at room temperature. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss law and modified Curie-Weiss law the Curie constant (C), Curie temperature (T_c) and a critical exponent of nonlinearity (γ) were calculated. The Curie temperature of doped samples were ranged from 128 to 130°C. The Curie constant for all series of samples decrease with increase of dopant concentration and the lowest values were observed on samples doped with 0.01 wt % of holmium.