Synthesis and characterization of BaZrO3 nanoparticles by citrate-nitrate sol-gel auto-combustion technique: Systematic study for the formation of dense BaZrO3 ceramics

Citrate-nitrate sol-gel auto-combustion method, employing high purity (≈99.999%) precursors, is adopted for the synthesis of BaZrO₃ nanoparticles. TGA-DSC, PXRD, SEM, TEM and BET techniques are used to explain (1) thermolysis of gel, (2) optimization of thermal parameters for phase pure BaZrO₃ nanoparticles of unimodal size-distribution and (3) microstructural evolution at the sintering stage. Complexation of citrates with cations in the gel is confirmed with the help of FTIR and solid-state MAS-¹³C-NMR spectrometry. Dried gel undergoes self-sustained combustion and finally resulted in white colour ashes. Ashes on further calcination at 1000 °C-8 h resulted in BaZrO₃ powder with an average crystallite size of 69.5 nm, as calculated by microstrain-domain size analysis of XRD of BaZrO₃ using Rietveld refinement. The crystallite size is consistent with SEM and TEM particle size analysis. The powder is sintered without any sintering-aid to achieve the highest density (99%) ever reported, compared to similar processes reported earlier.