Simultaneous influence of Mg2+and Sc3+co-doping on upconversion luminescence and optical thermometry in beta-NaYF4: Yb3+/Ho3+microphosphor

A series of xMg2+/ySc3+ co-doped beta-NaYF4:0.2Yb3+/0.02Ho3+ (x = y = 0 -0.2) upconversion (UC) green phosphors are synthesized using EDTA-assisted hydrothermal method. The structure, morphology and elemental compositions are investigated in detail using different experimental techniques. The lengthwise suppression of crystal due to co-doping is associated to the kinetics involved in the crystal growth in presence of Mg2+/Sc3+. The effect of Mg2+/Sc3+ co-doping on the UC green emission of beta-NaYF4:0.2Yb3+/ 0.02Ho3+ microphosphors is studied and about 31-fold enhancement in the green emission (5F4,5S2 -> 5I8) is observed for the 0.08Mg2+/0.12Sc3+ co-doped phosphor. The downconversion properties of the phosphors is also discussed to showcase the dual mode luminescence. The temperature sensing performance is in-vestigated using luminescence intensity ratio (LIR) technique for non-thermally coupled levels (5F5/5F4,5S2) of Ho3+ ions and maximum relative sensitivity of 0.258% K-1 at 374 K is obtained for the optimized phos-phor. The microphosphor can be sustained at high temperature as the UC emission intensity retains about 65% and 36% at 423 K and 574 K. From chromaticity diagram, the maximum color purity of 91.37% is obtained for 0.08Mg2+/0.12Sc3+ doping concentration. The estimated thermal parameters and color purity of Mg2+/Sc3+ co-doped beta-NaYF4:0.2Yb3+/0.02Ho3+ UC phosphors suggest their applicability in fabricating temperature sensors and LEDs. (c) 2022 Elsevier B.V. All rights reserved.