Rare-earth doped solid-state phosphor with temperature induced variable chromaticity

摘要

A temperature induced variable chromaticity phosphor based upon a rare-earth multi-doped solid-state frequency upconverter is presented. The phosphors are composed of ytterbium-sensitized multiple doped(Tm, Er, Ho) leadcadmium fluorogermanate glass samples excited by a laser source around 1064 nm. The temperature induced color variation exploits the heat enhanced effective absorption cross-section of the ytterbium sensitizer under multiphononassisted anti-Stokes excitation. The temperature enhancement of the energy-transfer mechanism between the sensitizer and the appropriate active light emitter ion allows the selective intensity control of the RGB emission wavelengths due to different upconversion excitation routes. The suitable combination of rare-earth active ions yielded the generation of variable chromaticity light with CIE-1931 coordinates changing from CIE-X=0.283;Y=0.288 at 20°C to CIEX=0.349; Y=0.412 at 190 °C, and CIE-X=0.285;Y=0.361 at 25°C to CIE-X=0.367;Y=0.434 at 180°C in Yb~(3+)/Tm~(3+)/Ho~(3+) and Yb~(3+)/Tm~(3+)/Er~(3+) multidoped samples, respectively. The viability of producing a low cost solid-state changeable visible color remote distributed temperature indicator in the 25°C - 300°C range is also discussed.