Enhanced upconversion emission in Nd, Yb, Er and Ho tetra-doped Y2O3 phosphor

Yb³⁺, Nd³⁺, Er³⁺ and Ho³⁺ tetra ions doped Y₂O₃ upconversion phosphors have been prepared by the combustion route. Crystalline phase purity and cubic phase of prepared samples have been confirmed from powder X-ray diffraction study. Absorbance of samples over spectral range 200–1100 nm has been measured by diffuse reflectance spectroscopy. All samples exhibit large band gaps. Scanning electron micrograph analysis reveals spherical morphology of particles and sizes around 200 nm. Upconversion emission has been studied under a 980 nm diode laser excitation with 166 mW laser power. The Ho³⁺, Nd³⁺ and Yb³⁺ co-doped Y₂O₃ phosphor show very high emission intensity of a green band centred at around 550 nm and another moderate intensity red band centred on 667 nm, while reverse is the case for Er³⁺, Nd³⁺ and Yb³⁺ co-doped Y₂O₃ phosphor. Er³⁺, Ho³⁺, Nd³⁺ and Yb³⁺ co-doped Y₂O₃ phosphor show enhanced high emission intensity in both green and red bands. These two bands are not visible in Nd³⁺ and Yb³⁺ co-doped Y₂O₃ phosphor but show weak upconversion emission at 549, 568 and 799 nm. Owing to the high emission intensity of green band, Ho³⁺, Nd³⁺ and Yb³⁺ co-doped Y₂O₃ phosphor may find potential applications in medical and security, while Er³⁺, Ho³⁺, Nd³⁺ and Yb³⁺ co-doped phosphor showing enhanced upconversion in green and red bands may find applications in white light generation.