A comparative study on electrical conduction properties of Sr-substituted Ba1-x Sr x Zr0.1Ti0.9O3 (x=0.00-0.15) ceramics

The lead-free polycrystalline Sr-substituted Ba1 - x Sr (x) Zr0.1Ti0.9O3 (BSZT) (x = 0.00-0.15) ceramics are synthesized by the high-temperature conventional solid-state reaction method. The Rietveld refinement of the X-ray diffraction pattern confirms the co-existence of tetragonal and cubic phase in the sample at x = 0.10, which is also confirmed from Raman spectroscopy. The surface micrographs show the formation of grains with well-defined grain boundaries and the significant enhancement in granular size with increasing Sr content. Moreover, the domain structure with lamellar and watermark characters is clearly observed for all the concentrations. The complex impedance analysis shows a significant increment in the net impedance of BSZT samples for the composition, x = 0.10. Exceptionally high value of impedance is attributed to the co-existence of two competing phases in the microscopic level. An enhancement in the impedance value is a consequence of reduction in the electrical conductivity of the sample. The modulus analysis confirms the presence of non-Debye-type relaxation in the material. The frequency gap (Delta f) between the normalized master curve ZaEuro(3)/ZaEuro(m)(3) and MaEuro(3)/MaEuro(m)(3) decreases with increasing Sr concentration, which indicates a reduction in the polarization in BSZT samples. This result is well consistent with the results obtained from the complex impedance analysis.