In-situ synthesis of samarium activated MgO–LaAlO3 nanocomposite for enhanced and prolonged phosphorescence

Abstract

A series of MgO–La1-xAlO3:xSm (x = 0–5 mol.%) nanocomposite phosphors have been synthesized in-situ using Pechini sol-gel method. The rhombohedral and face-centered crystal structures of LaAlO3 and MgO, respectively, were corroborated utilizing X-Ray Diffractograms and their Rietveld refinement. The optical band gaps of these nanocomposites have been observed in the range of 5.20–5.63 eV. Upon excitation by n-UV 405 nm radiation, the emission characteristics of these phosphors spanning 450–750 nm have been thoroughly investigated. The most notable emission occurred at 599 nm in the orange region, confirmed by CIE-1931 chromaticity coordinates. The MgO–La1-xAlO3:xSm (x = 2 mol.%) is found to be the optimum concentration exhibiting maximum luminescence with a high color purity of 90 %. Insights from Riesfeld's theory pointed towards d-q multipolar interactions as the underlying mechanism behind concentration quenching observed beyond this optimum concentration. Bi-exponential decay behavior was observed via Time-Resolved Photoluminescence (TRPL) technique, with an Internal Quantum Efficiency of 63 % calculated utilizing Auzel's formalism. The study extensively explored the impact of MgO addition on the crystallite size, band-gap, luminescence, and life-time properties, attributing the enhanced and prolonged luminescence behavior to the MgO–La1-xAlO3:xSm (x = 2 mol.%) nanocomposite. Assessment of additional parameters such as CCT (Correlated Color Temperature) and energy transfer efficiencies further reinforced the suitability of these orange emissive phosphors for potential applications in photonics and forensics, underlining their promising prospects in various technological domains.