Novel cadmium substituted barium zinc niobate perovskites: Phase formation, structural and impedance studies

Abstract

Herein we report the structural and impedance properties of the novel Cd-substituted perovskites, Ba(Zn1/3-xCdx)Nb2/3O3 (BZCN), 0 ≤ x ≤ 0.333, prepared by solid-state reaction at 1000 °C for 17 h. The doping mechanism of this complete substitutional solid solution was proposed to be a one-to-one replacement of Zn2+ by Cd2+ as to maintain the overall electroneutrality of the system. BZCN perovskites crystallised in a cubic symmetry, space group Pm3m, Z = 1 and their refined lattice constants, a = b = c were found to be in the range 4.0917(3)-4.1693(13) Å. A moderate unit cell expansion was discernible with increasing CdO concentration, thus portraying a linear correlation between lattice constant and composition that obeyed the Vegard's law. The surface microstructures of these BZCN perovskites were composed of irregular polyhedral grains and their determined crystallite sizes by both Scherrer and Williamson-Hall methods were found to be in the range 21.0–44.8 nm. Both TGA and DTA analyses also confirmed that these materials were thermally stable as neither phase transition nor weight loss was discernible within the studied temperature range 30–1000 °C. BZCN perovskites were highly insulating with high activation energies in the range ~ 2.51–3.19 eV. At 1 MHz and 30 °C, the recorded dielectric constants and losses were found to be ~ 24–29 and ~ 0.24–0.38, respectively.

Keywords

• Ceramics
• Dielectrics
• Perovskites
• Solid solutions