Effect of Gd3+ Ion Insertion on the Crystal Structure, Photoluminescence, and Dielectric Properties of o-Mullite Nanoparticles

摘要

Nanocrystalline Gd3+-doped Gd (x) Al6-x Si2O13 mullite powders with x from 0.005 to 0.025 have been synthesized via a facile coprecipitation technique. X-ray diffraction results revealed that o-mullite was detected as the major phase for x = 0.0 to 0.01, whereas corundum alpha-Al2O3 was predominant for x = 0.025. It was found that the volume of the mullite unit cell increased with Gd3+ ion incorporation. Differential scanning calorimetry thermograms evinced that the exothermic peak temperature of mullite shifted to lower values with Gd3+ ion insertion. Transmission electron microscopy observations of pure mullite nanoparticles displayed orthorhombic-like shapes. Meanwhile, at 0.5% Gd3+ ion content, the mullite particles exhibited platelet-like shapes, which distorted into spheroidal-like crystals at high Gd3+ ion contents (1% and 2.5%). The photoluminescence spectra indicated that the intensity of the emission spectra improved considerably with Gd3+ ion doping. On the other hand, dielectric measurements of sintered samples showed that the maximum dielectric loss values were 1.7 and 1.4 at 1.5 MHz and 1.5 GHz, respectively, with 2.5% Gd3+ ion content.