Rise time-based phosphor thermometry using Mg4FGeO6:Mn4+

Abstract

The rise time method is a time-resolved temperature measurement technique based on phosphorescence. Its short measurable time and high uncertainty limit its application. In this study, a long-term excitation on the millisecond level was used on the phosphor Mg4FGeO6:Mn4+ to realize a low uncertainty rise-time-based phosphor thermometry. A 385 nm UV-LED was used as excitation light and a high-speed camera was used as the detector. The results of calibration show that Mg4FGeO6:Mn4+ has a long rise time from 1140 ms to 2920 ms which is directly related to the temperature and has a low uncertainty of 1.2% in the temperature range of 293 K to 623 K. High absolute sensitivity of 3.02 μs K−1 was found at 623 K, and it increased with the decrease of temperature, reaching 7.65 μs K−1 at 293 K. To evaluate the effort of the excitation light on the rise time, the rise time of Mg4FGeO6:Mn4+ was measured with different excitation time and excitation energy. The results show that the rise time of Mg4FGeO6:Mn4+ is stable with different excitation times and decreases a little with the increase of the excitation energy. Finally, the rise time-based phosphor thermometry using Mg4FGeO6:Mn4+ was successfully applied on a 2D temperature measurements of jet impingement cooling. This is the first time of using MFG with a long-term excitation as the rise time-based phosphor thermometry. The high sensitivity and low-uncertainty demonstrate that Mg4FGeO6:Mn4+ has excellent performance for rise-time-based phosphor thermometry.