Photoluminescence characterizations in phase transition alumina with boehmite nanostructures

Abstract

The phase transition alumina γ, ẟ, θ, α with boehmite nanostructure have been prepared, and a relative study between the crystal structure, annealing temperature, and photoluminescence properties are reported in this paper. The effects of different temperatures up to 1600 ℃ on the boehmite nanostructure revealed different phases of alumina which are characterized using X-ray diffraction (XRD) technique. The evolution of crystal micrographs and grain size during the transformation are studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The emission spectra of the obtained samples are investigated using photoluminescence (PL) spectroscopy in which the traces of inherent impurities of Cr3+ are detected in the α-Al2O3 without any doping. The XRD and SEM/TEM analysis show that with increasing temperature, the transformation of boehmite into a well-crystallized α-Al2O3 and the micrographs from nanoplatelets with spindle-like edges to vermicular structure take place. Thus, this paper reports an important role of temperature in the phase transition, morphologies, and in the photoluminescence properties of the obtained samples. The optical properties investigate the defects associated with each phase of alumina in the transition alumina material system. The considerable sign of the crystal phase found that the emission band spectra of the corresponding phase vary greatly due to the presence of traces of uncontrolled impurity like Cr3+ found in the sample. The most prominent peak corresponding to the ruby laser has been found due to these Cr3+ ions in the most stable phase, α-Al2O3 which is the final product.