Ceramic samples of multicomponent fluoride compounds of cubic syngony: NaCaAlF, NaCaMgAlF and NaCaAlF doped with Eu ions were synthesized by solid-phase reactions. In these fluorides, Eu dopant ions have significantly different local environments and, as a result, different spectral and temperature properties of broadband 4f5d – 4f(S) and narrowband 4f(P) – 4f(S) luminescence. In particular, in NaCaMgAlF a weak 4f – 4f Eu luminescence band is observed only at low temperatures, in NaCaAlF a 4f – 4f luminescence band with a peak intensity comparable to that of the 5d – 4f Eu luminescence band is observed in the spectrum up to sufficiently high temperatures of ~650 K, whereas in NaCaAlF 4f – 4f Eu luminescence is absent in the spectrum in the entire studied temperature range of 77–670 K. The observed differences in the luminescence properties of Eu in synthesized fluorides are due to the different relative energy positions of the emitting 4f(P) and 5d states of Eu in different fluorides, as well as the presence of two or more Europium centers with different optical properties in some fluorides. The temperature dependence of the Eu luminescence intensity in synthesized fluorides in the region of strong temperature quenching in the range of 400–500 K can potentially be used for luminescent thermometry with a maximum relative sensitivity of up to 3%.
Khaidukov et al. (Wed,) studied this question.