Role of higher valent substituent on the dielectric and optical properties of Sr0.8Bi2.2Nb2O9 ceramics

Abstract

The synthesis, structure, optical and dielectric properties of strontium deficient bismuth excess strontium bismuth niobate Sr0.8Bi2.2Nb2O9 (SBNex) ceramics were systematically studied with tungsten and molybdenum as a doping element. The ceramics were prepared with a two-step solid-state method with of relative density. The XRD spectrum established that the orthorhombic crystal structure of the Aurivillius oxides was formed and doped with 2.5 at. % of W and Mo resulted in a near phase transition to the tetragonal phase. The energy dispersive X-ray spectra confirmed the formation of the desired compound of strontium deficient bismuth excess SBNex ceramic. The W doped SBNex ceramics exhibited the maximum value of dielectric constant at the lower frequencies. The dielectric study suggested that the relaxation mechanism be of Debye model with free from any space polarization. The complex modulus plots presented to establish the dielectric relaxation at higher frequency side of the spectra. The band-gap energy (Eg) decreased with Mo and W doping, being 3.00 and 2.85 eV respectively. The enhanced dielectric properties in W and Mo doped SBNex ceramics entitled them for the application to produce high density RAM.