Winning wide-temperature-range and high-sensitive thermometry by a multichannel strategy of dual-lanthanides in the new tungstate phosphors

Abstract

Abstract Both high sensitivity and wide temperature range are vital guides for up-conversion (UC) thermometers. However, high sensitivities were limited to a very narrow temperature range in existing optical thermometers. Also, the highest sensitivity usually occurred at elevated temperatures, while the sensitivity at room temperature or below it is very low or scarce. To overcome such a state, a novel optical thermometer with high sensitivities over a wide temperature range was designed. Lanthanide-doped UC phosphors with LiCaYb(WO4)3 (LCYW) as a novel host, were synthesized by a solid-state reaction process. Temperature sensing properties were carried out by a fluorescence intensity ratio (FIR) technique. High sensitivities of 0.01–0.0191 K-1 over the temperature range of 288–663 K were obtained in LCYW:0.03Er phosphor, which originated from the energy levels of Er3+ (2H11/2/4S3/2). Then, the thermal coupling levels (TCLs) and non-thermal coupling levels (NTCLs) were used to study the temperature sensing properties by co-doping Tm3+ ion. Excellent temperature sensing sensitivities were achieved, which are the higher sensitivities of 0.01–0.0216 K-1 over the range of 253–663 K based on the same TCLs of 2H11/2/4S3/2 and the highest sensitivity of 0.0563 K−1 at 663 K based on the NTCLs of 4S3/2 (Er3+)/3F2,3 (Tm3+). Besides, a multichannel strategy that mentions both sensitivity and temperature range was provided. Thus, the resulting new sensor can be operated in the wide temperature sensing range of 163–663 K with sensitivities of 0.011–0.0563 K-1. All of the results suggest that the LCYW:Er/Tm UC phosphor could be a good candidate with its high sensitivities for optical thermometry and as a safety sign in low and high temperatures.