Combustion Synthesis of Nanocrystalline Ba1.3Ca0.7SiO4 Semiconductors Using Urea as an Energy Efficient Fuel

Abstract

The τ-phase Ba1.3Ca0.7SiO4 alkaline earth silicate powders were synthesized using the solution combustion technique. For this purpose, metal nitrate–urea mixtures were used as an oxidant and a fuel. Urea’s main function was to help lower the nominal combustion temperature (~550 °C) of the mixtures through exothermic reactions, leading to a relatively mild post-annealing temperature (~750 °C). If the urea concentration increased, the interconnected silicate particle size decreased with nanoscale crystallite (average, 33 ± 3 nm), affecting optical properties. Finally, the photoluminescence spectra suggested that the light emission was through trap sites, because the emitted blue and green lights (2.6 and 2.3 eV, respectively) were smaller than the bandgap (~3.2 eV) of the Ba1.3Ca0.7SiO4 semiconductor.