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 20-30?m, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2- 10?m. Dielectric measurements were carried out as a function of temperature up to 180?C. The low doped samples sintered at 1380?C, display the high value of dielectric permittivity at room temperature, 2400 for 0.01Ho/BaTiO3. A nearly flat permittivity-response was obtained in specimens with higher additive content. Using a Curie-Weiss low and modified Curie-Weiss low the Curie constant (C), Curie temperature (Tc) and a critical exponent of nonlinearity (?) were calculated. The obtained value of ? pointed out that the specimens have almost sharp phase transition.
Highlights
A modified BaTiO3 with different additives/dopants is the most extensively investigated dielectric material due to its attractive properties that can be used on a large scale of applications
BaTiO3 powder is usually mixed with additives in order to adjust the sintering parameters and electrical properties to the requirements of electronic
Ho2O3 doped BaTiO3-ceramics were used for microstructure and electrical characterization
Summary
A modified BaTiO3 with different additives/dopants is the most extensively investigated dielectric material due to its attractive properties that can be used on a large scale of applications. The most commercial use is for multilayers capacitors, whereas BaTiO3 with semiconducting properties is used widely in electronic devices such as thermistors, varistors and energy converting systems. BaTiO3 powder is usually mixed with additives in order to adjust the sintering parameters and electrical properties to the requirements of electronic. Devices [1,2] It has been found, that the dielectric properties of polycrystalline BaTiO3, depend in a great extent on the grain growth during sintering and on donor type and concentration [3,4,5]. Two types of dopants can be introduced into BaTiO3: ions with larger ionic radii of valence 3+ and higher such as Ho3+, Er3+, and Dy3+, which replaces predominately Ba2+ sites in perovskite BaTiO3 lattice, and the ions with smaller ionic radii of valence 5+ and higher (Nb5+), can be incorporated into the Ti4+ sublattice [6,7,8,9]
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