Composition Regulation Triggered Multicolor Emissions in Eu2+-Activated Li4(Sr1–xCa1+x)(SiO4)2 for a Highly Sensitive Thermometer

We report on the development of a new class of highly sensitive luminescent optical thermometers building blocks via engineering multicolor-emitting Eu2+-activated Li4(Sr1–xCa1+x)(SiO4)2 phosphors. Since the Eu2+ ions occupied two diverse sites in the host, the resultant compounds emitted two distinct emissions in blue and yellow regions. In particular, the blue emission is ascribed to the Sr2+ sites, while the yellow emission is attributed to Ca2+ sites. By adjusting the content ratio between Ca2+ and Sr2+ ions, the emitted color can be changed from yellowish-brown to blue upon 365 nm excitation. Furthermore, with the aid of the fluorescence intensity rate technology, the temperature-sensing ability of the synthesized phosphors is revealed by means of detecting the inequable responses of the blue and yellow emissions to the temperature. When x = 0.4, the maximum relative sensitivity of the developed samples is 1.181% K–1. Importantly, the sensor sensitivities of the resultant phosphors can be adjusted by engineering the composition. These features elaborate that the Eu2+-activated Li4(Sr1–xCa1+x)(SiO4)2 phosphors with high sensor sensitivities present as one of most promising candidates for noninvasive optical thermometers.