Laser-Induced Tunable White Light Emission in Yb³⁺/Er³⁺/Tm³⁺ Ion-Doped La₂Ti₂O₇

A series of compounds with the general formula (La_1−xRE_x)₂Ti₂O₇ (x = 0.005, 0.015, and 0.025) doped with Yb³⁺, Er³⁺, and Tm³⁺ rare Earth ions were prepared by the traditional solid-state reaction at 1350 °C for 24 h. The X-ray powder diffraction technique, high-resolution transmission electron microscopy, and photoluminescence spectroscopy technique were used to characterize the structure and optical properties of the compounds. All compounds showed a single-phase orthorhombic structure with a space group Pna2 _1, as confirmed by JCPDS (Cart No: 01-070-1690). The La_1.9Yb_0.04Er_0.01Tm_0.05 Ti₂O₇ nanocrystals exhibited intense tunable white light luminescence signals in the full spectrum, and green and blue emissions were predominant in the Yb³⁺/Er³⁺⁻ and Yb³⁺/Tm³⁺-doped titanates, respectively. In this study, the influence of concentration and excitation power on the upconversion luminescence, color, and calculated laser-power-induced heating performance of La₂Ti₂O₇ nanophosphors were investigated at room temperature.