Preparation and Microstructural Characterization of Niobium Pentoxide Doped Barium Strontium Titanate Glass and Glass-Ceramics

Abstract

(Ba0.2Sr0.8)TiO3-2SiO2-B2O3-K2O compositions based glass and glass-ceramics with and without 0.1 mol% Nb2O5 were prepared by melt-quench method. XRD and FTIR spectra reveal the formation of amorphous structure and the presence of stretching and deformation vibration bonds of B-O-Si linkage and Si-O-Si bridges, respectively. Differential scanning calorimetry (DSC) of the glass sample shows that onset of crystallization for (Ba0.2Sr0.8)TiO3 phase occurs between ∼750o and 800°C. XRD confirms the formation of (Ba0.256Sr0.744)TiO3 as major phase upon controlled crystallization of the glass samples at ∼750o-800°C for 3 h with rutile and SiO2 as minor phase(s). Quantitative phase analysis using structural Rietveld refinement of the powder XRD patterns shows that 0.1 mol% Nb2O5 addition in the [(Ba0.2Sr0.8)O.TiO2]-[2SiO2-B2O3]- [K2O] glass-ceramic system promotes the formation of Ba0.256Sr0.744TiO3 phase and suppresses the amount of rutile or TiO2 compared to undoped glass-ceramic system. SEM-EDS microstructural analysis of undoped glass-ceramic illustrates the formation of micrometer size flower-like Ba0.256Sr0.744TiO3, and needle-shape TiO2 crystals. However, addition of 0.1 mol% Nb2O5 changes the crystals to irregular shape. Results from the dielectric measurements performed from room temperature to 250°C show that dielectric constant increases slightly with the addition of 0.1 mol% Nb2O5 compared to undoped glass-ceramic samples.