Upconversion luminescence of Sr 8 MgY(PO 4 ) 7 :Yb 3+ –Er 3+ /Ho 3+ phosphors for optical thermometry

In this work, to develop new upconversion (UC) luminescent material for optical thermometry, the Sr 8 MgY(PO 4 ) 7 :Yb 3+ –Er 3+ /Ho 3+ phosphors were explored, and their UC luminescence properties upon 980 nm excitation were investigated. The phase purity of the samples was checked by XRD patterns, which showed no secondary phase existed. For Yb 3+ –Er 3+ codoped samples, three peaks including two green and one red emissions have been found, and the optimal Er 3+ doping content was determined to be 3 mol% with regard to the green emissions. For Yb 3+ –Ho 3+ codoped samples, the green and red emissions demonstrated different change with Ho 3+ concentration, which could be owing to the cross-relaxation in Ho 3+ ions. By studying the temperature-dependence of the emission intensities, it was suggested that several strategies can be used for temperature sensing, involving the I 521 /I 548 and I 660 /I 521 of Er 3+ and I 658 /I 548 of Ho 3+ . The absolute and relative sensitivities were evaluated and the Yb 3+ –Ho 3+ codoped sample showed the higher sensitivities than Yb 3+ –Er 3+ codoped sample. The above results indicated the present phosphors could be candidate luminescent materials for optical thermometry.