Effect of Annealing Temperature on Structural, Photoluminescence and Thermal Properties of Nanosized Zirconium Silicates

Nanocrystalline powders of zirconium silicates with molar ratio 0.5:0.5 were prepared at room temperature by sol gel wet chemical route. As-prepared samples were annealed at 650, 875 and 1100 C for 4 h. Structural parameters of annealed powdered samples were determined by X-ray diffraction. The crystallite size was calculated using Debye-Scherrer formula as well as Williamson-Hall relation and then compared. Other structural parameters such as lattice constants, micro-strain, dislocation density etc. were also estimated. The FTIR spectra reveal the functional groups of the constituent atoms such as Zr, Si, 0 and OH which throw light on the expected structure. In the observed PL spectra, two PL components with peaks around 2.5 eV and 2.8 eV have been induced in zirconium silicates by the irradiation of photons at 8.0 eV. The relaxation of electrons (or holes) excited by ultraviolet photons to the upper state of luminescent centers, and then de-excitation to the lower state induces the PL components. The thermal analysis suggested that the decomposition of intermediate compounds occurred in different stages; and hydroxyl groups as well as residual organic impurities were removed successively and hence the prepared glasses became more and more dense.