Luminescence and dielectric investigations of crystalline niobate nanoceramics prepared through aqueous chemical process

Abstract

The present study reflects the synthesis of MgNb2O6 using hydrofluoric acid via a wet chemical approach, followed by characterizations involving XRD, electron microscopy, Raman spectroscopy, optical analyses, and impedance spectroscopy. The crystallite size of the synthesized material was determined to be 44 nm through XRD analysis. The lattice parameters of MgNb2O6 a, b, and c, were found to be 14.1998 Å, 5.6844 Å, and 4.9813 Å, respectively. Raman spectroscopy identified molecular bonds ranging from 253 to 1011 cm−1, mainly indicating the presence of metal oxide bonds. EDX spectra confirmed the presence of Mg, Nb, and O atoms in the prepared ceramics, indicating phase purity. FESEM analysis revealed a grain size of approximately 48 nm, with the presence of agglomerated grains. Bright spots in the SAED pattern observed by HRTEM confirmed the crystallinity of the prepared niobate materials, with the HRTEM microstructure showing a particle size near 49 nm. The crystallite size by XRD, grain size by FESEM, and particle size by HRTEM are in accordance with each other. The direct band gap was determined to be approximately 2.76 eV using UV-Visible spectroscopy. Additionally, MgNb2O6 materials exhibited a broad and strong photoluminescence emission near 445 nm with excitation at 270 nm, possibly indicating the presence of radiative defects in the crystalline nanostructure. Furthermore, impedance studies conducted between 40 and 110 MHz demonstrated a decrease in the dielectric constant at higher frequencies, reaching 21.06 at 110 MHz. A low dielectric loss was also observed at 110 MHz. The moderate band gap and strong room-temperature photoluminescence in the visible range make magnesium niobates suitable for possible applications in optical devices. This investigation shows that a dielectric constant near 21 and low dielectric loss can be achieved in the high-frequency range around 110 MHz.