A solid-solution modulation strategy in trivalent bismuth-doped gallate phosphors for single substrate tunable emission

Abstract

The synthesis conditions of most phosphors doped with lanthanide ions with d–f transition require a reducing atmosphere. The doping Bi³⁺ ions selected in this study perfectly avoid this requirement, and they are environmentally friendly and safe. Nevertheless, the spectral tuning of Bi³⁺ is a great challenge that limits its application. Herein, by regulating the value of x in the new solid solution Sr_2+xLa_1−xGaO_5−xF_x, the luminescence of Bi³⁺ is well promoted. Through an excitation-driven strategy, the emission peak position of Bi³⁺ is redshifted, and the luminescence of trivalent bismuth is successfully adjusted, which can also be applied to anti-blue lighting. In addition, we constructed a Bi³⁺–Eu³⁺ dual luminescence system, and, regardless of changes in the Bi³⁺/Eu³⁺ concentration or excitation wavelength, a single matrix white light phosphor was realized. Through calculations, the activation energy of the phosphor doped with 2.5%Eu³⁺ was found to be 0.257 eV, which is higher than the activation energy of some common compounds. This indicates that the phosphor has good application prospects in the field of solid-state lighting. It is worth noting that based on the different thermal response behaviors of Bi³⁺ and Eu³⁺, when the Eu³⁺ content is fixed at 1%, the maximum relative sensitivity of the optical thermometer based on its fluorescence intensity ratio is about 1.46% K⁻¹ at 383 K, which is higher than that of Bi³⁺ and Eu³⁺ co-doped phosphors previously reported. We also obtained a high absolute sensitivity of 0.00139 K⁻¹ at 403 K. Therefore, we also studied the thermal sensitivity of Bi³⁺ and Er³⁺ co-doped solid solutions. The results show that this solid-solution phosphor has far-reaching application prospects in the temperature sensing field.