Energy transfer in Cr and Nd co-doped Si-B-Na-Al-Ca-Zr-O glasses

•A novel silicate glass doped with both Cr and Nd was fabricated.•Cr could allow more efficient excitation of Nd by sunlight.•We determined the energy transfer efficiency from Cr to Nd.•This glass could have applications in solar pumped lasers for solar energy storage. Cr and Nd co-doped glasses are potential gain media for solar pumped lasers (SPLs). Tanabe-Sugano analysis shows that Cr doped Si-B-Na-Al-Ca-Zr-O (SBNACZ) glass contains a mixture of Cr3+ with octahedral coordination and Cr6+with unknown coordination. The crystal field parameters for Cr3+ were Dq = 1574 cm−1, B = 792.2 cm−1, C = 3005 cm−1 and Dq/B = 1.99, indicating a low covalency of Cr-O bonds. We compared the quantum efficiency (QE) of Nd and Cr co-doped SBNACZ glass with Nd doped SBNACZ glass to determine the Cr3+→Nd3+ transfer QE. The Cr2O3 content was fixed at 0.1 mol.% and the Nd2O3 content was varied between 0.1 and 1 mol.%. A maximum transfer QE of 20% was obtained at 0.5 mol.% Nd2O3. Cr3+→Nd3+ energy transfer is dominated by the coulombic interaction mechanism. The clustering of Nd3+ was a limiting factor for increasing the transfer QE with higher Nd3+ concentrations.