Structural and optical properties of thermal decomposition assisted Gd2O3:Ho3+/Yb3+ upconversion phosphor annealed at different temperatures

The infrared to visible upconversion fluorescent nanoparticles of Ho3+/Yb3+ codoped Gd2O3 phosphor is synthesized via thermal decomposition route. The as-synthesized sample was annealed at 800, 1000 and 1200 degrees C for 3 h and then structural and optical properties were studied. The Rietveld refinement of X-ray diffraction (XRD) data was analyzed to probe the effect of Ho3+/Yb3+ dopant on the structural parameters of Gd2O3 host. The upconversion emission spectra of as-synthesized and annealed samples are compared using 980 nm diode laser excitation and five emission bands noticed at 490, 539, 550, 667 and 757 nm corresponding to the F-5(3) -> I-5(8), F-5(4) -> I-5(8), S-5(2) -> I-5(8), F-5(5) -> I-5(8) and I-5(4) -> I-5(8) manifolds, respectively. The local temperature induced by laser light is also calculated. The fluorescence intensity ratio (FIR) of two thermally coupled transitions F-5(4) -> I-5(8) and S-5(2) -> I-5(8) is plotted against the sample temperature and sensor sensitivity of sample is calculated. (C) 2016 Elsevier B.V. All rights reserved.