Low temperature synthesis of nanocrystalline proton conducting BaZr0.8Y0.2O3-δ by sol-gel method

Nanoceramic powders of proton conducting BaZr0.8Y0.2O3-delta, (BZY20) have been prepared at low crystallization temperature (below 130 degrees C) by sol-gel synthesis using all-alkoxide route. Due to a very low crystallization temperature, hydroxyl defects in the lattice crystal are incorporated in-situ during the synthesis process as confirmed by the gradual decrease in the lattice constant from 4.227 to 4.200 angstrom on annealing from X-ray diffraction (XRD) analysis, OH vibrations observed in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis, and weight loss and heat exchange reaction observed by TG/DTA analysis. The results of XRD have revealed well-crystallized BZY20 peaks of this advanced ceramic material even at low processing temperature. Analysis of FT-Raman spectrum taken at room temperature for the nanocrystalline BZY20 samples prepared at 130 degrees C using sol-gel processing has revealed an ideal Pm3m cubic crystal symmetry. However, a very slight distortion due to the difference in the B-site sublattice is also observed in the FT-Raman spectrum of the samples upon annealing at higher temperatures. SEM images show the microstructural evolution of the powders from agglomerated nanoscaled crystallites to the nanosized pseudospherical morphology with diameter less than 50 nm. The present low temperature synthesis can be successfully applied to other oxide protonics materials highly doped with protonic defects. (C) 2007 Elsevier B.V All rights reserved.