Size effect and order–disorder phase transition in MgAl₂O₄: synthesized by co-precipitation method

We report on the size effect and order–disorder phase transitions in MgAl₂O₄ system synthesized by chemical co-precipitation method. The prepared samples were sintered at various temperatures (in steps of 200 °C). Initially, the order–disorder phase evolution of the cubic spinel aluminates were analyzed by powder X-ray diffraction and UV-absorbance spectral analysis. The optical band gap was calculated from UV–DRS absorbance spectra. Also, the grain size of the sintered aluminates was calculated by high resolution scanning electron microscopy through surface morphological image analysis and discussed. Moreover, the particle size was calculated by using transmission electron microscopy. The stretching and bending mode of tetrahedral and octahedral coordinates for vibration modes of cations were studied through Fourier transform infrared spectral analysis. In addition, the cation distributions in the prepared samples were carried out by solid-state nuclear magnetic resonance spectroscopic measurement and analyses. The frequency dispersive behavior of dielectric constant was analyzed at room temperature for the synthesized samples using impedance analyzer. The observed results are discussed and reported.