ABSTRACT
Luminescence probes that facilitate multimodal non-contact measurements of temperature are of particular interest due to the possibility of cross-referencing results across different readout techniques. This intrinsic referencing is an essential addition that enhances accuracy and reliability of the technique. A further enhancement of sensor performance can be achieved by using two luminescent ions acting as independent emitters, thereby adding in-built redundancy to non-contact temperature sensing, using a single readout technique. In this study we combine both approaches by engineering a material with two luminescent ions that can be independently probed through different readout modes of non-contact temperature sensing. The approach was tested using Al2O3 co-doped with Cr3+ and Mn4+, exhibiting sharp emission lines due to 2E â 4A2 transitions. The temperature sensing performance was examined by measuring three characteristics: temperature-induced changes of the intensity ratio of the emission lines, their spectral position, and the luminescence decay time constant. The processes responsible for the changes with temperature of the measured luminescence characteristics are discussed in terms of relevant models. By comparing temperature resolutions achievable by different modes of temperature sensing it is established that in Al2O3-Cr,Mn spectroscopic methods provide the best measurement accuracy over a broad temperature range. A temperature resolution better than ±2.8 K can be achieved by monitoring the luminescence intensity ratio (40-145 K) and the spectral shift of the R-line of Mn4+ (145-300 K range).
ABSTRACT
The results of X-ray diffraction studies of the Gd(Mg0.95-x,ZnxMn-0.05)B5O10 down-converting phosphor as a function of Mg-Zn composition are presented. The lattice parameters and unit cell volumes of GdMg0.95-xZnxMn0.05B5O10 pentaborates are examined. The relationships between the structure and optical properties of these materials are explicated based on the results of theoretical calculations of the energy structure. The effect of pressure on the luminescence of Mn2+ in this system was studied up to ca. 32 GPa. The observed quenching of Mn2+ luminescence is due to the crossing of the emitting 4T1g level with the non-emitting 2T2g state. This crossing sets a long-wavelength limit on the possibility of observing the emission of Mn2+ ions, which is around 850 nm.
