Yb³⁺-activated phosphate glasses melted with MnCO₃ for solar spectral conversion

This paper reports on the physical and optical properties of phosphate glasses containing red-emitting Mn²⁺ and near-infrared (NIR)-emitting Yb³⁺ ions of interest for solar spectral conversion. The glasses were prepared by melting with 50P₂O₅-(48 – x)BaCO₃–2Yb₂O₃-xMnCO₃ (x = 0, 1, 2, 3, 4 mol%) formulas, and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), UV–Vis-NIR spectrophotometry, and photoluminescence (PL) spectroscopy. The glasses were X-ray amorphous with the various characteristic features of phosphate glasses being evident in the FT-IR spectra. The thermal properties of the co-doped glasses assessed by DSC appeared similar despite the variation in manganese content. The optical absorption spectra supported the occurrence of Mn²⁺ ions while Mn³⁺ was detected at high MnCO₃ content. The NIR absorption due to Yb³⁺ ions was nonetheless consistent with the fixed Yb₂O₃ content. The PL evaluation showed that sensitized Yb³⁺PL was attained under Mn²⁺excitation at 410 nm where the NIR emission increased with MnCO₃ content in connection with Mn²⁺→ Yb³⁺ energy transfer. However, the NIR emission output realized with 4 mol% MnCO₃ was just marginally higher than the obtained with 3 mol% MnCO₃. On the other hand, the red Mn²⁺emission was highest for 3 mol% MnCO₃. Thus, considering the optimized red and NIR emissions while minimizing absorption by Mn³⁺, the Yb-containing glass melted with 3 mol% MnCO₃ was put in perspective with the concept of solar spectral conversion.