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Abstract: Phosphor powders of Yb3+ co-doped BaZrO3:Er3+ have been prepared by the urea combustion route. The formation of single-phase BaZrO3:Er3+ and BaZrO3:Er3+,Yb3+ was confirmed by X-ray powder diffraction (XRD). Green and red luminescence along with a weaker blue emission is observed upon excitation at ∼978nm with a diode laser. These emissions are caused by frequency upconversion in the Er3+-doped BaZrO3 (BZO) phosphor. Both the green and red upconversion emissions of the Er3+ are enhanced by about ∼3 and ∼43 times respectively when triply ionized ytterbium is incorporated as a co-dopant. The frequency upconversion processes responsible for the blue, green and red emissions are discussed on the basis of the experimental data. [Copyright &y& Elsevier]

Abstract: Using the combustion synthesis, CaYAl3O7:Er3+ phosphor powders co-doped with Yb3+ have been prepared at low temperatures (550°C) in a few minutes. Formation of the compound was confirmed by X-ray powder diffraction. Near-infrared to visible upconversion fluorescence emission in the Er3+ doped CaYAl3O7 phosphor powder has been observed. The effect of co-doping with triply ionized ytterbium in the CaYAl3O7:Er3+ phosphor has been studied and the process involved is discussed. [Copyright &y& Elsevier]

Abstract: Tb3+ doped CaZrO3 has been prepared by an easy solution combustion synthesis method. The combustion derived powder was investigated by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy techniques. A room temperature photoluminescence study showed that the phosphors can be efficiently excited by 251nm light with a weak emission in the blue and orange region and a strong emission in green light region. CaZrO3:Tb3+ exhibits three thermoluminescence (TL) glow peaks at 126°C, 200°C and 480°C. Electron Spin Resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TL peaks. The room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0233 is identified as an O− ion. Centre II with an axial symmetric g-tensor with principal values g =1.9986 and g ˔=2.0023 is assigned to an F+ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal annealing experiments and this centre (assigned to F+ centre) seems to originate from an F centre (oxygen vacancy with two electrons). The F centre and also the F+ centre appear to correlate with the observed high temperature TL peak in CaZrO3:Tb3+ phosphor. [Copyright &y& Elsevier]