Luminescence thermometry with transition metal ions. A review

Transition metal (TM) ion activated phosphors are increasingly being used as probes for luminescence thermometry. Their luminescence is characterized by strong absorption and emission bands that span the visible and near-infrared spectral ranges and are highly susceptible to temperature variations. Due to the latter characteristic, sensitive and reliable remote temperature measurements can be performed by observing temperature-induced changes in TM ion emission intensities, emission bandwidths and bandshifts, and excited state lifetimes, as well as the temperature dependences of the intensity ratios between various emission bands in single or double activated phosphors. This review provides a systematic analysis of the performances of luminescent thermometers based on different TM ions and discusses the relations among the TM spectroscopic properties, characteristics of the host material structure, and thermometric performance. Particular attention is given to the engineering of energy transfer between TM and other dopant ions to obtain highly sensitive thermometers. Finally, several typical application examples from recent literature are highlighted.