Studying the effects of composition and sintering parameters on dielectric properties of tantalum oxide doped barium titanate

Abstract

The research aimed at optimizing the composition and sintering parameters of Ta2O5 doped BaTiO 3 ceramics to enhance its dielectric properties. For conducting the research, BaTiO3 was dopedwith Ta2O5 in the range of 0.5-1.5 mole %. At first, nano sized pure BaTiO3 and Ta2O5 were milled, dried and pressed into pellets to prepare the green samples. Then the green samples were fired in a high temperature furnace for densification. Both single and double stage sintering was used for densification of the samples. Thereafter SEM and XRD techniques were used to examine the structure of the sintered samples with particular focus on the incorporation of Ta5+ ions into the BaTiO3crystal lattice. During XRD analysis, the X-ray diffraction peaks of (111), (200) and (002) planes of BaTiO 3 and (220) plane of Ta2O5 were investigated. The SEM analysis was focused on measuring grain size andinvestigating grain size distribution of the sintered samples. Following the SEM analysis, EDX analysis was conducted for elemental analysis and to understand the diffusion process of Ta5+ in the BaTiO3crystallattice. Finally, dielectric properties of the samples were measured using an impedance analyzer. Finally, a correlation was established between the dielectric properties of the sintered samples and their microstructure. From the research, it can be concluded that single stage sintering in the range of 12500C to 13000C for 2hrs proved insufficient for diffusion of Ta5+ ion into the lattice. As a result, Ta2O5 gave strong pinning effect and resulted in poor dielectric properties of doped BaTiO3 ceramics. However, double stage sintering proved to be effective for diffusion of Ta5+ ion into the latticeand enhancing the dielectric properties of Ta2O5 doped BaTiO3 ceramics. The best room temperature dielectric constant of 22,000-23,000 was obtained for 1.5 mole% Ta2O5 doped BaTiO3 sintered at 13100C for zero hours and 12800C for six hours. Such high dielectric constant was achieved due to the combination of high %theoretical density and optimum grain size at this sintering condition.At a temperature range of 300 to 600C, this combination of composition and sintering parameters yielded dielectric constant of around 21,000.In addition to enhancing dielectric constant, 1.0-1.5 mole % Ta2O5 stabilized the cubic phase of BaTiO 3. However, at certain sintering condition, even 0.5mole% Ta2O5 stabilized the cubic phase of BaTiO3.