Ratiometric Thermometry Using Thermochromic Tb:Mn:NaMg(WO) Phosphors.

The utility of Tb:Mn:NaMg(WO) phosphors as ratiometric luminescent thermometers in the 200-450 K temperature range is demonstrated. Targeted substitution of Tb for Na and Mn for Mg yields phosphors of formula NaTbMgMn(WO). UV excitation of the NaMg(WO) host results in green emission from terbium (544 nm) and red emission from manganese (682 nm). Differential thermal quenching of these emissions renders NaTbMgMn(WO) thermochromic between 78 and 450 K, with an orange-to-green color change that is particularly noticeable above 200 K. As a result, this phosphor serves as a ratiometric and colorimetric thermometer between 200 and 450 K. Quantitative assessment of its performance yields a maximum relative sensitivity of 2.5 × 10 K at 375 K, along with a resolution of 0.5 K and a repeatability of 98%. These findings highlight the versatility of NaMg(WO) as a platform to realize luminescent thermometers via targeted aliovalent substitutions.