Color-Tunable Upconversion Luminescence and Multiple Temperature Sensing and Optical Heating Properties of Ba3Y4O9:Er3+/Yb3+ Phosphors

Abstract

Upconversion (UC) luminescence materials doped with rare earth ions are extensively investigated as optical temperature probes by the fluorescence intensity ratio technique. However, most Er3+-doped materials are still suffering from low sensing sensitivity. In the present study, we attempt to develop high-sensing-sensitivity Er3+-doped materials based on the thermally coupled energy levels (TCLs) from Stark sublevels as well as the properties at subzero temperatures, for which there is continuous lack of research. Er3+/Yb3+ codoped Ba3Y4O9 (BYO) phosphors were produced via a solid-state reaction. Excited by 980 nm, various output colors, including bright green, yellow, and red, in BYO:Er3+/Yb3+ phosphors as well as the relative emission intensities could be regulated through altering Yb3+ concentrations. Subsequently, on the basis of all 12 pairs of TCLs especially from Stark sublevels of 2H11/2, 4S3/2, and 4F9/2 of Er3+ ions, multiple temperature-sensing performances are evaluated over a wide range of 73–573 K. The results show that the maximum sensitivity of the 2H11/2 and 4S3/2(1) levels is approximately 1-fold higher than that of traditional TCLs of 2H11/2/4S3/2 at elevated temperature and the maximum sensitivity based on the 2H11/2(1) and 2H11/2(2) levels is more than 12 times higher than that of the traditional TCLs of 2H11/2/4S3/2 at subzero temperature. Therefore, it is expected to realize high-sensitivity temperature detection from subzero to elevated temperatures by combining two pairs of different TCLs. In addition, the potential of Er3+/Yb3+ codoped BYO phosphors to be used as an optical heater is studied. The generated temperature can be accurately monitored by BYO:Er3+/Yb3+ phosphors and regulated by adjusting the excitation power, which indicate that BYO:Er3+/Yb3+ phosphors can be used as an optical heating device.