Structural and optical characterization of nanoparticulate manganese doped zinc silicate phosphors prepared by sol–gel and combustion methods

The present study reports the synthesis, crystallographic structure and optical properties of manganese (Mn²⁺) doped zinc silicate (Zn₂SiO₄) nanoparticle phosphors prepared by sol–gel and combustion methods. For samples prepared by sol–gel method, the X-ray diffraction results showed phase transformation from amorphous to α-phase Zn₂SiO₄ due to annealing temperatures at 600 °C to 1100 °C, whereas for combustion samples an admixture of highly crystalline β-phase and hexagonal wurtzite structure of ZnO was observed at annealing temperature of 600 °C. Photoluminescence spectra with Mn²⁺ concentrations ranging from 0.015–0.09 mol% were compared for two methods. Emission band assigned to the ⁴T₁(⁴G)→⁶A₁(⁶S) electronic transition of Mn²⁺ was observed with maximum intensity at ~573 nm for combustion samples and ~532 nm for sol–gel samples upon UV-excitation by a Xenon lamp. Furthermore, the photoluminescence decay curves of annealed Zn₂SiO₄:Mn²⁺ samples were observed to be bi-exponential. The fast and slow decay components are due to the pair or cluster formation and isolated ions at higher doping concentration, respectively.