Bandshift Luminescence Thermometry Using Mn⁴⁺:Na₄Mg(WO₄)₃ Phosphors

Abstract

The feasibility of employing Mn4+-activated phosphors for bandshift luminesence thermometry is demonstrated for the first time using Mn4+:Na4Mg­(WO4)3. Substitution of Mn4+ for Mg2+ in Na4Mg­(WO4)3 yields phosphors in which Mn4+ activators are distributed over (Na/Mg)2O10 dimers. Neutron powder diffraction reveals that metal–oxygen bond distances in these dimers are significantly longer than those typically observed in Mn4+-activated phosphors. Multisite distribution of Mn4+ activators coupled to long metal–oxygen distances impart thermometric functionality to Mn4+:Na4Mg­(WO4)3. Red emission from two distinct Mn4+ emitters leads to a broad band extending from 560 to 850 nm. Differential thermal quenching of these emitters drives a sigmoidal blueshift of the emission maximum upon increasing temperature from 100 to 400 K (ca. 30 nm); bandshift luminescence thermometry is thus realized. Quantitative assessment of the thermometric performance of Na4Mg0.940Mn0.030(WO4)3 yields a sensitivity of 0.127 nm K–1, a repeatability greater than 99%, and a temperature resolution of 2.5 K at 300 K. Findings presented in this article expand the scope of applicability of Mn4+-activated thermosensitive phosphors beyond ratiometric bandshape and lifetime thermometry. More importantly from the perspective of developing new phosphors, our results provide structural guidelines for discovering and screening novel oxide hosts for Mn4+ activators.

Pushing the Limit of Boltzmann Distribution in Cr3+-Doped CaHfO3 for Cryogenic Thermometry

“…The ratiometric strategy of using two different luminescence transitions allowed to overcome the limitations of the thermometers based on band shift , or single emission due to their power dependence and source intensity fluctuations. In this view, the main strategy considered for designing ratiometric luminescence cryogenic thermometers consists of the use of the ratio between the emissions coming from two different ions such as Tb 3+ and Eu 3+ − ,, or Er 3+ and Yb 3+ .…”

Tm2+ Activated SrB4O7 Bifunctional Sensor of Temperature and Pressure—Highly Sensitive, Multi‐Parameter Luminescence Thermometry and Manometry

“…The performance of the developed SrB 4 O 7 :Tm 2+ thermometer based on band-shift is comparable with the most sensitive Na 4 Mg 0.940 Mn 0.030 (WO 4 ) 3 sensor material reported before, which is based on the d-block metal ion, that is, Mn 4+ . [51] The performance of the other reported lanthanide-based band-shift thermometers is significantly inferior. Moreover, to the best of our knowledge, our sensor material presents the highest sensitivity among the reported lanthanide-based luminescent thermometers, when using the FWHM as a thermometric parameter (see Table 1).…”

“…The most reliable figure of merit for sensing based on band intensity ratio (as well as for the emission lifetimes) is relative sensitivity, S r , which is usually expressed in %, and shows how the measured parameter changes per 1 K of absolute temperature. [51] The corresponding S r values as a function of temperature were calculated according to Equation ( 1):…”

“…[58,59] The relative thermal sensitivity increases with temperature, until it reaches the maximal value of S r max = 4.16% K −1 at 337 K. Afterward, S r decreases to 3.36% K −1 at 400 K. As shown in Table 1, compared to other thermometers based on luminescence decay time, our material not only shows 4 parameters for temperature determination, but also, in each category, is one of the thermometers with the highest sensitivity within a relatively wide operating T-range. It is worth noting that the number of the reported optical thermometers in Table 1 are limited, due to the limited numbers reported for lanthanide or other transition metal ions based optical thermometer based on bandshift [32,48,51,60,61] and FWHM. [60][61][62] Please note that the developed sensor SrB 4 O 7 :Tm 2+ is a very rare case among luminescence thermometers, where the relative sensitivity based on the decay time is higher than that obtained using the LIR.…”

Dual-emission luminescence thermometry using LaGaO3:Cr3+, Nd3+ phosphors

“…LIR thermometers based on Cr 3+ , Mn 4+ , and Ni 2+ have been investigated, both as single and dual-doped systems. 11,22,23,24,25 The Boltzmann equilibrium between the closely separated 2 E and 4 T2 excited states of d 3 ions such as Cr 3+ underpins them. [26][27][28][29] The aim of the present study was to combine the complementary advantages of lanthanide and transition metal ions in the design of a luminescent thermometer that would function in the near-infrared (NIR) region.…”