Effects of synthesis temperature on the structural and optical properties of CaAl2O4: Eu2+, Dy3+nanoparticles

Abstract

Calcium aluminate phosphor nanomaterials co-doped with europium and dysprosium (CaAl2O4: Eu2+, Dy3+) were prepared using a facile solution combustion technique. The structural and optical properties were investigated. The X-ray diffraction (XRD) results confirmed the presence of the monoclinic phase in all the samples, with few impurity phases in the samples synthesized at 300 °C and 400 °C. The Fourier-transform infrared analysis gave the expected chemical combustion results of the final product with few traces of Ca3Al2O6 impurities at low and very high synthesis temperatures. The XRD patterns displayed diffraction angles of the major peaks shifting to higher 2 theta as the synthesis temperature increased. This is attributed to an increase in particle sizes, which led to an increase in lattice parameters. The intensity of the prominent peak increased up to 500 °C due to improved crystal quality. The crystallite sizes of the as-prepared samples were determined using the Debye-Scherrer equation. It was noted that there is variation in the crystallite sizes with synthesis temperature. The UV–Vis graph shows that absorption edges also shifted to lower wavelengths with an increase in synthesis temperature. It was noted that the band gap increased with an increase in synthesis temperature up to 500 °C, but at temperature of 1000 °C, the band gap was observed todecrease. Scanning electron microscope micrographs showed that the samples had irregular shapes with pores and cracks. The study provides a simple route to synthesize CaAl2O4: Eu2+, Dy3+phosphors with optimum synthesis temperature, producing the most crystalline sample for use in lighting devices.