Ho2O3 additive effects on BaTio3 ceramics microstructure and dielectric properties

Abstract

Doped BaTiO3-ceramics is very interesting for their application as PTCR resistors, multilayer ceramic capacitors, thermal sensors etc. 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. The samples were prepared by the conventional solid state reaction and sintered at 1320° and 1380°C in an air atmosphere for 4 hours. The grain size and microstructure characteristics for various samples and their phase composition was carried out using a scanning electron microscope (SEM) equipped with EDS system. SEM analysis of Ho/BaTiO3 doped ceramics showed that in samples doped with a rare-earth ions low level, the grain size ranged from 20-30μμm, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2-10μμm. Dielectric measurements were carried out as a function of temperature up to180 °C. The low doped samples sintered at 1380 °C, display the high value of dielectric permittivity at room temperature, 2400 for 0.01 Ho/BaTiO3. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss low and modified CurieWeiss low the Curie constant (C), Curie temperature (Tc) and a critical exponent of nonlinearity (γ) were calculated. The obtained value of γ pointed out that the specimens have almost sharp phase transition.