Effect of Y3+, Gd 3+ and La3+ dopant ions on structural, optical and electrical properties of o-mullite nanoparticles

Dielectric ceramics of M(x)Al6(1–x)Si2O13 doped mullite were synthesized via co-precipitation technique. The X-ray diffraction profiles revealed that these nanoparticles were crystallized well and the volume of mullite unit cell was increased as a function of the ionic radius of dopant ion. TEM images showed regular orthorhombic crystal morphology for the pure mullite sample. Meanwhile, the doped samples exhibited slightly distorted crystal morphology of larger particle sizes. DSC thermograms evinced that the exothermic peak temperature of mullite was shifted to the lower value with M3+ ion insertion. The photoluminescence spectra were studied for mullite samples, and it was found that the intensity of the emission spectra was affected by the M3+ ion type. It was found that, Y3+ doped mullite achieved the minimum dielectric loss value of 0.01 in the radio wave frequency region (1 MHz). Meanwhile, Gd3+ doped mullite achieved the minimum dielectric loss value of 0.09 in the microwave frequency region (1 GHz).