Synthesis, Characterization, Photoluminescence Properties of Rare-Earth Free Activated Sr2GeO4 for Lighting Applications
摘要
Strontium orthogermanate (Sr2GeO4) doped with Mn4+ and Cu2+ phosphors were prepared by high temperature solid state reaction. All the prepared phosphors were crystallized in the orthorhombic lattice with space group Pbn21. The surface morphology of prepared phosphors contains irregular shaped objects with considerable agglomeration. The FT-IR and Raman profiles of the compositions gave characteristic bands belonging to GeO44− tetrahedra. Photoluminescence profiles of Sr2GeO4: Mn4+ compounds are characterized by red emission at 647 nm upon excitation at 433 nm, while Sr2GeO4: Cu2+ compositions gave orange emission at 603 nm under excitation at 403 nm. The emission mechanism of Sr2GeO4: Mn4+ was explained by Tanabe-Sugano energy level diagram of Mn4+ ion. The CIE chromaticity coordinates, color purity (CP) and correlated color temperature (CCT) values were deduced. Thermoluminescence profiles are characterized and trap depth parameters were evaluated. These compositions may be useful in the manufacturing of cool and warm solid state lighting sources.