High dielectric permittivity of SrBi₂Nb₂O₉(SBN) added Bi₂O₃ and La₂O₃

Abstract

In this paper, the structural and dielectric properties of SrBi₂Nb₂O₉ (SBN) as a function of Bi₂O₃ or La₂O₃ addition level in the radio (RF) and microwave frequencies were investigated. The SBN, were prepared by using a new procedure in the solid-state reaction method with the addition of 3; 5; 10 and 15 wt.% of Bi₂O₃ or La₂O_3. A single orthorhombic phase was formed after calcination at 900 °C for 2 h. The analysis by x-ray diffraction (XRD) using the Rietveld refinement confirmed the formation of single-phase compound with a crystal structure (a = 5.5129 Å, b = 5.5183 Å and c = 25.0819 Å; α = β = γ = 90°). Scanning Electron Microscope (SEM) micrograph of the material shows globular morphologies (nearly spherical) of grains throughout the surface of the samples. The Curie temperature found for the undoped sample was about 400 °C, with additions of Bi³⁺, the temperature decreases and with additions of La³⁺ the Curie temperature increased significantly above 450 °C. In the measurements of the dielectric properties of SBN at room temperature, one observe that at 10 MHz the highest values of permittivity was observed for SBN5LaP (5%La₂O₃) with values of 116,71 and the lower loss (0.0057) was obtained for SBN15LaP (15%La₂O₃). In the microwave frequency region, Bi₂O₃ added samples have shown higher dielectric permittivity than La₂O₃ added samples, we highlight the SBN15BiG (15 % Bi₂O₃) with the highest dielectric permittivity of 70.32 (3.4 GHz). The dielectric permittivity values are in the range of 28–71 and dielectric losses are of the order of 10⁻². The samples were investigated for possible applications in RF and microwave components.