Band gap engineering and multicolor emission in environment friendly Dy-Ti Co-doped LiNbO3 ceramics for advanced electrical energy storage, LED and laser applications

Abstract

This research presents experimental data on the development of environmentally friendly ceramics (1-x)LiNbO3-x(Li0.5Dy0.5)TiO3 prepared through high-energy ball milling with varying compositions. Structural analysis, employing Rietveld structure refinement, reveals a consistent presence of a mixed phase, encompassing cubic and rhombohedral phases for compositions up to x = 0.2. Sintering at 1050 °C yields varied average grain sizes (3.46 μm–1.09 μm) with distinct compositions, displaying regular and consistent grain morphology. X-ray photoelectron spectroscopy spectra indicate presence of oxygen vacancies and reveal the oxidation states of elements such as O1−, O2−, Nb5+, Dy3+, Ti4+ and Ti3+. Dielectric properties are investigated across a wide frequency range (1 kHz–1 MHz) and temperatures up to 500 °C, revealing a frequency-dependent reduction in both dielectric constant and dielectric loss for all compositions. Ferroelectric properties at room temperature show enhancement with the maximum polarization reaching approximately 0.8 μC/cm2 for x = 0.1. A band gap reduction is observed with increasing Dy-Ti doping content and a minimum direct band gap of 3.13 eV is obtained for x = 0.2 composition. Photoluminescence analysis demonstrates the presence of yellow, cyan, and blue bands, valuable for yellow laser and light emitting diodes applications. The dielectric permittivity of (1-x)LiNbO3-x(Li0.5Dy0.5)TiO3 ceramics shows a better response with increase of temperature in frequency range 1 kHz to 1 MHz for all compositions than pure LiNbO3 and there is also no Curie temperature observed up to 500 °C for any composition this makes it a suitable candidate material for high temperature applications. We achieved a maximum recoverable energy storage density of 17.96 mJ/cm3. Overall, these findings provide valuable insights into the structural, electrical, and optical properties of the studied ceramics, suggesting their potential for development of high temperature phosphor materials for white LEDs, yellow lasers, energy storage and other high temperature technological applications. © 2025 Elsevier Ltd and Techna Group S.r.l.