Synthesis of nano Lead Tungstate (PbWO4) by Single Step Modified Combustion Process and Characterization for their application as LTCC and Optical Material

Abstract

NanostructredScheelitePbWO4were synthesized through a single step modified auto-ignition combustion technique. The X-ray diffraction, Fourier transform Raman and infrared spectroscopy studies revealed that the as-prepared samples were phase pure and the average crystallite size was ∼49 nm. PbWO4 crystallizes in tetragonal structure. The particle size and morphology of the sample was studied using transmission electron micrograph. The optical properties of the sample were studied using Ultraviolet-visible and photoluminescence spectra. The samples showed a maximum transmission in the visible regions but poor transmittance in the ultraviolet region. The optical band gap of the samples calculated using the Kubelka-Munk method was 3.87 eV, suggesting their semiconducting behavior. The photoluminescence spectra recorded on the samples showed that nano PbWO4 has visible luminescence. The thermal stability of the sample at elevated temperatures has been studied using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). No substantive weight loss were observed for the samples in the temperature range 50-900oC. The PbWO4 samples were sintered to 98% relative density at very low temperature of 787oC without using any sintering aid. The microstructure of the sintered pellets observed by Scanning Electron Micrograph (SEM) showed that the pellets were well sintered with minimum porosity. The dielectric constant (εr) of the sintered PbWO4 sample was recorded using an LCR meter in the range 50 Hz to 5 MHz and showed a value of 86 at 1 MHz with a loss factor of 10-2. The calculated temperature coefficient of dielectric constant is negative. The low sintering temperature, dielectric constant, low loss factor and negative temperature coefficient make the sample ideal for low temperature co-fired ceramic, electronic substrate materials as well as suitable for various optical applications such as UV filters, transparent films for window layers on solar cells, anti-reflection coatings, scintillators, detectors.