Physical, Thermal, and Optical Properties of Mn²⁺ and Nd³⁺ Containing Barium Phosphate Glasses

This work reports on various properties and analysis of optical interactions in phosphate glasses containing red-emitting Mn2+ and near-infrared (NIR)-emitting Nd3+ ions, which are of interest for energy applications and solar spectral converters. The glasses were made by melting with 50P2O5–(48 – x)BaO–2MnO–xNd2O3 (x = 0, 0.5, 1.0, and 2.0 mol %) nominal compositions and characterized by X-ray diffraction, density and related physical properties, differential scanning calorimetry, dilatometry, UV–vis–NIR optical absorption, and photoluminescence spectroscopy with decay kinetics analysis. The glasses were X-ray amorphous, wherein the physical and thermal properties of the Mn2+/Nd3+-codoped glasses were largely impacted by Nd2O3 contents. The optical absorption spectra supported the occurrence of Mn2+ ions and the lack of Mn3+ in the codoped glasses, while the absorption due to Nd3+ ions increased steadily with Nd2O3 contents. Analyzing the glass absorption edges via Tauc and Urbach plots was further pursued for a comparison. The photoluminescence evaluation showed a consistent suppression of the emission from Mn2+ ions with increasing Nd3+ concentration, while the decay kinetics revealed shorter lifetimes in connection with increased Mn2+ → Nd3+ transfer efficiencies. Excitation of Mn2+ at 410 nm, however, led to the Nd3+ NIR emission being most intense for 1.0 mol % Nd2O3, despite the 4F3/2 emission decay analysis showing lifetime shortening throughout. Considering the compromise between red and NIR emissions, the Mn-containing glass doped with 0.5 mol % Nd2O3 is put in perspective with the concept of solar spectral conversion.