Investigation on dielectric properties of Al2O3, ZnO and MgO doped Ba0.7Sr0.3TiO3 ceramics

Abstract

Being an insulator material with high relative permittivity, Barium Strontium Titanate (BST) ceramics can be used extensively in many applications if its dissipation factor is reduced. In this paper, we investigate dielectric properties of Ba0.7Sr0.3TiO3 ceramics when doped with Al2O3, ZnO and MgO. At first, Ba0.7Sr0.3TiO3 ceramics was synthesized using conventional solid-state reaction technique. Further the Ba0.7Sr0.3TiO3 ceramic samples were doped with 0.5, 1.0, 2.0, 4.0 and 8.0 wt% Al2O3. Similarly Ba0.7Sr0.3TiO3 ceramic samples were doped with same weight percentages of ZnO and then MgO. After making pellets of all these samples, silver paste was coated for top and bottom electrodes to form ceramic based Metal-Insulator-Metal (MIM) capacitors. The dielectric properties were measured at room temperature using Hioki 3532-50 LCR Hi-Tester. It is noted that relative permittivity increases with dissipation factor (dielectric loss) irrespective of doping material and doping concentration. The dissipation factor achieved by 2.0 wt% ZnO doped Ba0.7Sr0.3TiO3 ceramics is 0.0087, which is promisingly very low. Further it is observed that 2.0 wt% ZnO doped Ba0.7Sr0.3TiO3 ceramics possesses highest figure of merit (relative permittivity to dissipation factor ratio) and hence optimum performance among the doping materials and doping concentrations considered.