Unconventional Production of Bright White Light Emission by Nd-Doped and Nominally Un-Doped Nano-Powders

We report the production of a broad band (ranging from 400 to 900 nm) white light following the monochromatic infrared light (803.5 and 975 nm) excitation of both nominally un-doped and Nd³⁺-doped Y₂O₃ nano-powders, even up to 20% of Nd³⁺ content. Experimental results indicate that such emission feature is a nano-scale phenomenon, cannot be ascribed to an overlap of sharp emission bands in the un-doped case and, even if assisted by the Nd³⁴ presence, is a host matrix-related process. The measured white light emission is strongly dependent on either environment pressure (a pressure threshold occurs) or pumping power. The rising patterns of the white light emission were found to increase faster for either increasing Nd³⁺ content and pumping power or decreasing particle size. Notably, high correlated color temperature (2756 K), color rendering index (99), and efficiency (864 lx/W) values were measured for the un-doped sample under 803.5 nm exciting wavelength.