Microstructure and Dielectric Properties of Naturally Formed Microcline and Kyanite: A Size-Dependent Study

The present article reports the crystal defect-mediated changes in electrical characteristics, especially, dielectric properties, of naturally formed microcline and kyanite in two different size fractions. A facile top-down synthesis approach has been adopted to achieve the nanosized samples. Structural and morphological studies have been carried out using X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Phase purity and microstructural characteristics of the samples were investigated by performing the Rietveld refinement method. Microstructural analysis reveals that the sample size has been greatly reduced to the nano regime after the mechanical ball-milling process, and the milling process eventually introduced some defects in the nanosized samples. UV-vis spectroscopy reveals the optical absorption characteristics and the band gap values of the samples. A major outcome of the present study is the enhancement of the defect states naturally formed samples using the mechanical milling method and the defect-mediated electrical response with varying temperature and frequency. Remarkably high dielectric permittivity values (77.3 × 10³ for AF2 and 8.036 × 10³ for KY2) in the nanosamples along with low tangent losses and good industrial feasibility of synthesis make the nanosized samples a potential material for fabricating low-cost energy storage devices.