Luminescence of Ce doped MgAl2O4 prepared by the combustion method

Abstract

Magnesium aluminate (MgAl2O4) has received special attention as a technologically important material because of its attractive properties, such as mechanical strength, chemical inertness, a wideband gap, relatively low density, high melting point, high thermal shock resistance, low thermal expansion coefficient, resistance to neutron irradiation and low dielectric loss. It has also been used as a phosphor host activated by a variety of transition metal and lanthanide ions. A simple combustion method was employed for the preparation of Ce doped MgAl2O4 nanocrystals using metal nitrates as precursors and urea as a fuel in a preheated furnace at 520°C. The as-prepared samples were annealed in a hydrogen atmosphere to improve their optical properties. The samples thus obtained were characterized by X-ray diffraction (XRD), UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and photoluminescence spectroscopy (PL). The XRD data showed that all the samples had the spinel structure and the average particle size of the as-prepared samples was about 25nm. PL spectra of Ce doped MgAl2O4 using an excitation wavelength of 350nm produced broad green emission bands centred at 500nm. Maximum green emission was obtained for the sample doped with 0.75mol% Ce. UV–vis diffuse reflectance spectra and XPS were used to obtain more information on the conversion of Ce ions from the non-luminescent Ce4+ to the luminescent Ce3+ charge state.