Analyzing BST compositional variation with manganese additive for device temperature and bandwidth enhancement

摘要

The polycrystalline samples of 2% MnO_2 doped barium-strontium titanate (BST) were synthesized in various Ba/Sr ratio (0.8, 0.6, 0.4, 0.2) by a mixed oxide method (calcination temperature = 1150 ℃ for 8 h, sintering temperature = 1200 ℃ for 8 h) using high-purity ingredients (barium carbonate, strontium carbonate, titanium dioxide and manganese dioxide). Preliminarily structural analysis of the samples shows the existence of a major phase of perovskite and a minor phase of MnO_2. The lattice parameters of a major phase (orthorhombic system) and microstruc-ture of the ceramic samples were determined by powder X-ray diffraction and scanning electron microscopy analysis respectively. Significant modification in the dielectric properties (permittivity and tangent loss) of BST of different Ba/Sr ratios was observed on addition of even fixed amount of manganese dioxide. The composition ratios and additive dependent dielectric, impedance and related characteristics of the samples provide insight into the material behavior and modified capacitive and resistive parameters. The AC/DC conductivity spectra derived for the different compositions spell out clearly about the electrical processes and mechanism involved in the synthesized materials. This paper tries to bring out the unique structural and electrical features of the manganese oxide modified of Ba/ Sr (0.8, 0.6, 0.4 and 0.2). The observation of low dielectric loss and high bandwidth held promise for applications in tuned circuits.