Combinatorial optimization of the atomic compositions for green-emitting YBO₃: Ce³⁺,Tb³⁺ and red-emitting YBO₃:Ce³⁺,Tb³⁺,Eu³⁺ phosphors using a microplate reader

Microplate readers are versatile devices that can rapidly measure the photoluminescence intensities of multiple samples, and are widely used in biological chemistry. In this work, using a commercial microplate reader, we attempted to optimize the atomic compositions of green-emitting phosphor Y_1−x−yCe_xTb_yBO₃ and red-emitting phosphor Y_{1−x−y−z}Ce_xTb_yEu_zBO₃. We filled 48 individual wells of an alumina microplate with aqueous solutions of nitrates of Y³⁺, Ce³⁺, Tb³⁺, and Eu³⁺ with different compositions, and then added an aqueous solution of boric acid to each well. After drying, the microplate was heated at 550 °C for 2 h in air, and then at 1100 °C for 3 h in a reducing atmosphere. Y_1−x−yCe_xTb_yBO₃ absorbed near ultraviolet light through 4f → 5d transitions of Ce³⁺ and emitted green fluorescence corresponding to 4f → 4f transitions of Tb³⁺ through Ce³⁺ → Tb³⁺ energy transfer. Moreover, Y_{1−x−y−z}Ce_xTb_yEu_zBO₃ emitted red fluorescence corresponding to 4f → 4f transitions of Eu³⁺ through Ce³⁺ → Tb³⁺ → Eu³⁺ energy transfer under near-ultraviolet light. Measurement of the photoluminescence intensity of each well by a microplate reader revealed that the optimized green and red phosphors were Y_0.835Ce_0.025Tb_0.14BO₃ and Y_0.535Ce_0.005Tb_0.45Eu_0.01BO₃, respectively.