Promising light converting BaMoO4:Er3+-Tm3+-Yb3+ phosphors for display and optical temperature sensing

Er³⁺-Tm³⁺-Yb³⁺ tri-doped BaMoO₄ phosphors were synthesized by co-precipitation technique and characterized by X-ray diffraction analysis, absorption study and field emission scanning electron microscopy analysis. Upconversion as well as downconversion luminescence studies were performed by using near infrared (980 nm) and ultraviolet (380 nm) excitations. Energy level diagram, pump power dependence and colour coordinate study were utilized to describe the multicolor upconversion emission properties. Under single 980 nm diode laser excitation the dual mode sensing behaviour is realized via Stark sublevels and thermally coupled energy levels of the Tm³⁺ and Er³⁺ ions in the prepared tri-doped phosphors. A comparative fluorescence intensity ratio analysis for integrated emission intensities arising from the Stark sublevels {¹G_4(a) and ¹G_4(b)} and thermally coupled energy levels {²H_11/2 and ⁴S_3/2} of the Tm³⁺ and Er³⁺ ions, respectively was carried out in the prepared tri-doped BaMoO₄ phosphors. The maximum sensitivity for thermally coupled energy levels of the Er³⁺ and Stark sublevels of the Tm³⁺ ion was reported. The developed phosphors could be useful in the display devices and optical thermometric applications.