Influence of annealing temperature on structural, optical and electrical properties of zinc silicate (Zn2SiO4) nanophosphors

Zinc Silicate (Zn2SiO4) nanophosphors have been successfully synthesized by co-precipitation route. The structural, optical and electrical properties of Zn2SiO4 nanophosphors have been thoroughly investigated. The structural studies made using X-ray diffraction measurements exhibited that with increase in the annealing temperature of Zn2SiO4 nanophosphors, the crystallite size is found to increase from 20 to 28 nm and indicate higher lattice parameter with improved crystallinity with annealing temperature. FT-IR studies confirm presence of ZnO4 and SiO4 vibrational modes and confirm the formation of Zn2SiO4 nanophosphors with optimum visibility for annealed temperature of 1000 °C. The UV–Vis spectroscopy measurements reveal the maximum absorption peak associated with lowest bandgap of 5.53 eV is achieved for Zn2SiO4 nanophosphors at annealing temperature of 1000 °C. The photoluminescence emission spectra reveal that the Zn2SiO4 nanophosphors are self-luminescing in green spectral region at 520 nm and the emission intensity decreases with increase in annealing temperature. The color correlated temperatures (CCT) studies shows that the samples of Zn2SiO4 nanophosphors can be utilised for achieving cool white light applications and maximum CCT is achieved for Zn2SiO4 nanophosphor annealed at temperature of 1000 °C. The dielectric measurements reveal presence of interfacial polarization and following Maxwell–Wagner polarization & Koop's characteristics in Zn2SiO4 nanophosphors. In addition, highest permittivity and low dielectric loss is observed for Zn2SiO4 nanophosphors annealed at 900 °C and 1100 °C. The impedance Cole-Cole plots reveal non-Debye type relaxation in all Zn2SiO4 nanophosphors and decrease in the radius of the semicircles with increase in annealing temperature. A high resistive nature is observed for Zn2SiO4 nanophosphor annealed at 1100 °C. These results help in understanding the potential usage of these Zn2SiO4 nanophosphors for white light as well as microelectronic device applications.