Luminescent thermometry at a new level. Widening the temperature range of luminescent thermometers through the intra- and interconfigurational transitions of Pr3+

Different applications in nearly all fields require measurement of temperatures for various process analysis and controlling. Among the available temperature measurements methods, a pyrometer is a commonly used device. It determines the temperature of a medium based on the emitted thermal radiation. However, recent advances in technology have seen numerous improvements in not only pyrometers but also develop other methods for measuring temperatures.

Non-contact temperature measurements like radiation pyrometry are widely preferred over electrical contact methods. This is due to their excellent properties such as high upper-temperature limit, immunity to the surrounding environment and high response rate. Unfortunately, pyrometry experiences several limitations including flame interference and sensitivity to stray light that results in errors thus reducing their operational efficiency. As such, researchers have been looking for alternatives for overcoming the disadvantages of pyrometry and have identified luminescence thermometry as a promising solution. This, in particular, has attracted significant attention owing to its excellent properties including insensitive nature to electromagnetic interferences.

Currently, emerging technologies in the fields of biomedicine, photonics among others requires the use of non-contact and accurate temperature sensors. This required development of more efficient temperature sensors to meet the demands of accuracy, broad sensing range and thermal sensitivity. Despite studying several luminescent phosphors, it has been difficult to find a single composition with the potential for obtaining desired thermal sensitivity and accuracy in a wide temperature range. For instance, a narrow temperature range is a drawback for most of the available luminescent phosphorous materials.

Recently, a group of researchers led by Professor Luís António Dias Carlos at the University of Aveiro and Professor Eugeniusz Zych at University of Wroclaw exploited the possibility of widening the temperature range of luminescent thermometers. Briefly, the authors combined the intra-and interconfigurational transitions of the Pr³⁺ ion in a single material while using Sr₂GeO₄:Pr³⁺ for illustration. They purposed to enhance the performance of the sensor by implementing the luminescence thermometry in a broad temperature range and relatively high thermal sensitivity. Their work is published in the research journal, Advanced Optical Materials.

The authors observed that it was possible to widen the temperature range of the luminescent thermometers. For instance, the broadest temperature in the range of 16-600K was noted. Consequently, the overall performance of the sensor was significantly increased with a maximum relative sensitivity of up to 9.0%, 0.6% and 0.5% for the cryogenic range, physiological range and high-temperature range were noted. Moreover, the minimum temperature uncertainty of 0.1K was noted. Furthermore, the thermometer remained three times as effective in high temperatures as compared to the conventional infrared thermographic systems thus confirming their efficiency in offering high-temperature range measurements.

The study is the first to cover such a broad temperature range. Thus, they successfully demonstrated that the inter- and intraconfigurational of Pr³⁺ transitions are effective for widening the temperature range of luminescent thermometers. Therefore, the study will advance the fabrication of high-performance temperature sensors with desired properties to meet the increasing demand for various application in different fields.