Influence of annealing temperature on material properties of red emitting ZnGa2O4: Cr3+ nanostructures

Abstract

Zinc gallate (ZnGa2O4) nanopowders doped with Cr3+ (1 mo%) were synthesized by the citric acid assisted sol–gel method. The influence of annealing temperature, structural, morphological, and optical properties of ZnGa2O4: Cr3+ (1 mol%) nanosized particles were investigated. The X-ray diffraction (XRD) spectra indicated that the nanoparticles are cubic in structure and the annealing temperature did not influence any c in structure. The average crystallite size of ZnGa2O4: Cr3+ nanoparticles were observed to increase from 11.85 to 30.88 nm as the annealing temperature increased from 600 to 1000 °C. The scanning electron microscopy (SEM) showed nearly spherical nanostructures that change in size with annealing temperature. The high resolution transmission electron microscope (HR-TEM) images show well resolved lattice fringes which is an indications of highly crystalline samples. Ultraviolet–visible (UV–Vis) measurement show decrease in reflectance in visible region and energy band gap was found to decrease with annealing temperature. The photoluminescence (PL) intensity was found to be maximum for sample annealed at high temperature (1000 °C) and least with sample annealed at low temperature (600 °C). An increase in annealing temperature leads significantly increment in PL intensity. The degree of crystallinity also increased with annealing temperature from XRD, SEM, and HR-TEM analysis. The photoluminescence lifetimes, particle size, and emission spectra are comparable with reports on bioimaging applications. In this paper, we provide the insights on the “Influence of annealing temperature on material properties of red emitting ZnGa2O4: Cr3+ nanostructures”. It is found that: