Change in structural morphology on addition of ZnO and its effect on fluorescence of Yb³⁺/Er³⁺ doped Y₂O₃

Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er(3+)/Yb(3+) nano-crystalline phosphor

Infrared-to-visible upconverting rare earths Er(3+)/Yb(3+) co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532 nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555 K under 976 nm laser excitation.

Efficient visible upconversion luminescence in Er3+ and Er3+/Yb3+ co-doped Y2O3 phosphors obtained by solution combustion reaction

Combustion derived Er(3+) -doped Y2O3 and Er(3+)/Yb(3+)co-doped Y2O3 powders have been characterized by X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and laser excited spectroscopy. Formation of Y2O3 phosphor was confirmed by X-ray diffraction and energy dispersive X-ray analysis. The vibrational properties of Y2O3 powder was studied by Fourier transform infrared spectroscopy. The luminescence spectra of Er(3+) -doped and Er(3+)/Yb(3+) co-doped Y2O3 powders were studied under 379nm excitation. The strong up-conversion luminescence for Er(3+) -doped and Er(3+)/Yb(3+) co-doped Y2O3 powders have been observed under 978nm laser excitation. The effect of Yb(3+) addition on optical and luminescence properties of Er(3+):Y2O3 powders were studied. The ratio of red to green intensity has been enhanced when Er(3+) -doped Y2O3 is co-doped with Yb(3+) ions. The effect of co-doping of Yb(3+) ions on the visible luminescence intensity of Er(3+) has been studied and the mechanism responsible for the variation in the green and red intensity is discussed.

Anomalous luminescent properties in ZnO and SrAl2O4composites

We showed a phase transformation from high temperature hexagonal phase to most stable monoclinic phase of SrAl₂O₄by incorporating 20% of ZnO in ZnO and SrAl₂O₄composite (Singhet al.2014Dalton Transactions). The composite with monoclinic phase further showed the intense near band edge emission and defect band emission corresponding to ZnO without any signature of SrAl₂O₄in PL spectra. An energy band diagram responsible for defect band emission is proposed for the composites.