Thermally-coupled Levels Research Articles

BiLaWO6: Er3+/Tm3+/Yb3+ phosphor: Study of multiple fluorescence intensity ratiometric thermometry at cryogenic temperatures

Highly thermally stable Er3+/Tm3+/Yb3+ tri-doped bismuth lanthanum tungstate phosphors were prepared by high temperature solid-state reaction method. The structural and morphological properties of the prepared phosphors were analysed by X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM) coupled with energy dispersion spectrum (EDS). Visible upconversion (UC) luminescence was measured by exciting the phosphors with 980 nm laser radiation. The dependence of the UC intensity of each emission band of Er3+ and Tm3+ ions as a function of temperature in the range from 30 to 300 K was monitored. Fluorescence intensity ratios (FIR) of thermally coupled levels (TCL) and non-thermally coupled levels (NTCL) were analysed and verified with appropriate theoretical validation. The absolute (SA) and relative sensitivities (SR) were estimated and compared with the reported systems. In the present case of BiLaWO6: Er3+/Tm3+/Yb3+, SR (0.43 % K−1) related to TCL of Er3+ UC is found to have maximum sensitivity compared to any of the NTCL combinations at 300 K. From this study we inferred that the SR values estimated from NTCL are smaller than that of TCL involved in BLW: Er3+/Tm3+/Yb3+ phosphor. The temperature dependent CIE color coordinates were also evaluated in the cryogenic temperature region.

Ratiometric dual-center Gd2O3:Tb3+/Eu3+ nanothermometers with enhanced thermometric performances

Ratiometric luminescence thermometers based on thermally coupled levels provide reliable temperature sensing with predictable calibration. However, requirement of thermal coupling of levels limits possible energy gap between them, and as, a result, leads to a fundamental limitation of relative thermal sensitivity. Development of luminescence thermometers with two active centers could overcome this drawback and obtain sensors with enhanced thermometric characteristics. Here, we suggested two types of dual-center Gd2O3:Tb3+/Eu3+ nanophosphors, namely co-doping and physical mixture, for ratiometric thermometry within temperature range of 123–473 K. Monitoring luminescence intensity ratio between Tb3+ and Eu3+ bands provides contactless sensing with moderate relative thermal sensitivities (0.53–0.77 % K−1) and sub-degree temperature resolution (0.3–0.6 K) at room temperature. All studied thermometers irrespective to dispersion system type and doping concentration display exceptional relative sensitivity exceeding the theoretical limit of sensors based on thermally-coupled levels at high temperatures. The largest sensitivity was determined to be 5.6 % K−1@473 K for mixed Gd2O3:Tb3+ 0.01 at. %+ Gd2O3:Eu3+ 0.2 at. % sample.

Thermally enhanced near-infrared luminescence in CaSc2O4: Yb3+/Nd3+ nanorods for temperature sensing and photothermal conversion

Non-invasive photothermal therapy (PTT) is proposed as a powerful method for cancer treatment, in which a precise temperature monitoring is strongly recommended during the photothermal conversion process to prevent the damage of normal cells. Herein, ultra-sensitive optical thermometry with excellent resolution and outstanding light-to-heat conversion are simultaneously realized in CaSc2O4: Yb3+/Nd3+ nanorods. The temperature sensing of the nanorods is accomplished through fluorescence intensity ratio (FIR) technology based on the thermally coupled levels (TCLs) Nd3+: 4Fj (j = 7/2, 5/2, 3/2), of which the obtained absolute sensitivity is about 6.5 times larger than the optimal value of TCLs-based thermometers reported previously. Meanwhile, an intense thermal enhancement of Nd3+: 4Fj (j = 7/2, 5/2, 3/2) → 4I9/2 transition is found due to the efficiency improvement of phonon-assisted energy transfer process between Yb3+ ions and Nd3+ ions. The penetrability of the near-infrared light emitting by Nd3+ ions is determined by a simple ex vivo experiment, indicating a penetration depth of 8 mm in the biological tissues with negligible effect on FIR values. Beyond that, the nanorods show remarkable photothermal conversion capacity under the excitation of 980 nm wavelength. The properties mentioned above show enormous potentiality of the present nanorods for PTT along with a real-time temperature sensing.

Boltzmann vs. non-Boltzmann (non-linear) thermometry - Yb3+-Er3+ activated dual-mode thermometer and phase transition sensor via second harmonic generation

Second harmonic generation (SHG) and upconversion luminescence (UCL), as second-order nonlinear optical (NLO) effects, are crucial in modern optics and optoelectronics. Here, through the chemical engineering process we obtained a series of optically active BaTiO3: Er3+, Yb3+ perovskite materials, exhibiting temperature-dependent NLO responses. Upon 976 nm laser light irradiation, the micron-sized, polycrystalline samples show simultaneously intense UCL and SHG effects. Comparison of the thermometric features based on luminescence thermometry, i.e., band intensity ratio based on thermally-coupled levels of Er3+, and NLO thermometry, i.e., SHG/UCL intensity ratio, shows that the superior thermal sensitivity (≈ 4%/K, at ~400 K) and excellent temperature resolution (δT = 0.07 K) is achieved for the NLO thermometry approach. Furthermore, the combination of NLO spectroscopy with UCL allows rapid, more precise and clear phase transition detection (from tetragonal to cubic phase at around 386 K), compared to conventional structural methods, such as X-ray diffraction and Raman spectroscopy. Our work suggests that some non-Boltzmann, non-linear thermometers can provide much more effective temperature readouts (compared to the commonly studied Boltzmann thermometers), simultaneously working as accurate, rapid and non-invasive phase transition sensors.

Multi-functionalities of photoluminescence, X-ray excited luminescence and optical temperature sensing in Er3+ and Er3+/Yb3+ doped Gd2Zr2O7 phosphors

A series of Er3+-doped and Er3+-Yb3+ co-doped Gd2Zr2O7 phosphors were synthesized via hydrothermal method, and their multifunctional properties were studied in detail. The Raman spectra indicated that the products were the ordered pyrochlore phase of Gd2Zr2O7, which exhibited a good radiation resistance. The up-conversion (UC), down-conversion (DC) photoluminescence (PL) and X-ray excited luminescence (XEL) spectra of the Er3+: Gd2Zr2O7 samples showed the similar spectra profiles, which were composed of the prominent green (2H11/2/4S3/2→4I15/2) and weak red (4F9/2→4I15/2) emissions. The co-doping of Yb3+ ions was beneficial for the improvement in UC PL but led to the reductions in DC PL and XEL. Besides, the X-ray induced green emissions demonstrated a high-sensitivity to the dose rate and a long-term stability against the continuous X-ray irradiation. Moreover, using the fluorescence intensity ratio (FIR) technique, the temperature sensing behaviors were analyzed based on the thermally coupled levels (TCLs) 2H11/2 and 4S3/2 of Er3+. The FIRs were found to be insensitive to the excitation power variation, and the optimal relative sensing sensitivity reached ~1.1%K−1 at 298 K. These characteristics may enable the studied system applicable for optical thermometry, X-ray detection and X-ray imaging.

Dual-center co-doped and mixed ratiometric LuVO4:Nd3+/Yb3+ nanothermometers

During last decade luminescence thermometry has become a widely studied research field due to its potential applications for real time contactless temperature sensing where usual thermometers cannot be used. Special attention is paid to the development of accurate and reliable thermal sensors with simple reading. To address existing problems of ratiometric thermometers based on thermally-coupled levels, LuVO4:Nd3+/Yb3+ thermal sensors were studied as a proof-of-concept of dual-center thermometer obtained by co-doping or mixture. Both approaches to create a dual-center sensor were compared in terms of energy transfer efficiency, relative sensitivity, and temperature resolution. Effect of excitation mechanism and Yb3+ doping concentration on thermometric performances was also investigated. The best characteristics of S r = 0.34% K−1@298 K and ΔT = 0.2 K were obtained for mixed phosphors upon host excitation.

Optical temperature sensing by tuning photoluminescence in a wide (visible to near infrared) wavelength range in a Eu3+-doped Bi-based relaxor ferroelectric.

The prevalent material design principles for optical thermometry primarily rely on thermally driven changes in the relative intensities of the thermally coupled levels (TCLs) of rare-earth-doped phosphor materials, where the maximum achievable sensitivity is limited by the energy gap between the TCLs. In this work, a new, to the best of our knowledge, approach to thermometric material design is proposed, which is based on temperature tuning of PL emission from the visible to the NIR region. We demonstrate a model ferroelectric phosphor, Eu3+-doped 0.94(Na1/2Bi1/2TiO3)-0.06(BaTiO3) (NBT-6BT), which, by virtue of the contrasting effects of temperature on PL signals from the host and Eu3+ intraband transitions, can achieve a relative thermal sensitivity as high as 3.05% K-1. This model system provides a promising alternative route for developing self-referencing optical thermometers with high thermal sensitivity and good signal discriminability.

Visible and near-infrared luminescence properties of Nd3+/Yb3+ co-doped Gd2O3 phosphors for highly sensitive optical thermometry.

Phosphors with rare earth (RE) ions are widely applied to optical temperature measurements. Moreover, the near-infrared (NIR) emission of phosphors has potential applications in the biological field. Herein, Gd2O3:x%Nd3+/Yb3+(0.2 ≤ x ≤ 0.8) samples are successfully synthesized by the sol-gel method, and their phase and morphology are characterized. The XRD data are refined by Rietveld. Under 980 nm continuous wave (CW) laser excitation, the upconversion (UC) and downshift (DS) emissions are studied. The temperature sensing performances of thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs) of Gd2O3: Nd3+/Yb3+ phosphors are investigated through the fluorescence intensity ratio (FIR) technology. In the temperature range of 303-523 K, the maximum relative sensitivity of I761 nm/I550 nm reaches 6.54% K-1, which is based on non-TCLs. At the same time, the maximum relative sensitivity of I761 nm/I1000 nm-1500 nm reaches 3.13%. In addition, the influence of the laser induced heating (LIH) effect is studied. Compared with square wave (SW) pumping, the relative sensitivity would decrease at CW excitation. Finally, the durability and temperature uncertainty are also discussed. The results prove that the Gd2O3:Nd3+/Yb3+ samples present higher relative sensitivity and durability and lower temperature uncertainty in the biological window. Therefore, the phosphors can be used as optical thermometers in the biological field.

Cr3+-doped double-perovskites for near-infrared luminescent ratiometric thermometry

The accurate measurement of temperature is of great importance in many fields ranging from industrial manufacture to our daily life, which can be finely implemented via the fluorescent intensity ratio (FIR) thermometry on the basis of Boltzmann distribution. Especially, the near-infrared (NIR)-emitting levels 4T2/2E of Cr3+ ion have recently emerged as the promising thermally coupled levels (TCLs), taking advantage of their superior optical property with high tunability. Herein, the crystal field strength around Cr3+ ions in double-perovskite La2MgHfO6 have been elaborately modulated via varying the dopant concentration, which greatly affect the intensity ratio between the spin-forbidden 2E → 4A2 and spin-allowed 4T2 → 4A2 transitions. Thermal sensing behaviors based on the TCLs (4T2/2E) were evaluated and the relative sensitivity gradually grew with the increase of crystal field strength. Above results offer guiding insights into the sensitivity optimization of Cr3+-based FIR thermometers, while providing the possibility of highly accurate measurement of temperature.

Mixed-valent MgAl2O4:Eu2+/Eu3+ phosphor for ratiometric optical thermometry

Novel strategies to obtain remote temperature sensing with good spatial and thermal resolution are in high demand in various applications, where traditional thermometers are inappropriate. The majority of developed luminescence thermometers utilize thermally-coupled levels with their inherent limitation of thermal sensitivity and problems with signal discriminability. We report mixed-valent Eu2+/Eu3+-doped MgAl2O4 phosphor as a ratiometric thermal sensor, which is free of these drawbacks. Different temperature behavior of Eu2+ and Eu3+ emission bands provides luminescence thermometry within range of 298–523 K. High absolute and relative thermal sensitivities of 0.084 K-1 and 0.83% K−1, respectively, as well as sub-degree temperature resolution indicate that MgAl2O4:Eu2+/Eu3+ phosphor is a promising material for optical thermometry.

Luminescent lanthanide nanocomposites in thermometry: Chemistry of dopant ions and host matrices

• Current progress on luminescent lanthanide nanocomposites for thermal sensing. • Effect of host matrices on thermometry. • Impact of dopant ions and their emission transition on thermal sensitivity. • Modern challenges in nanothermometry development. Recently, there has been observed huge progress in the advancement of remote optical nanothermometry, as it plays a vital role in remote, noninvasive, and remote temperature sensing, which is especially important for various bio-applications, e.g., in theranostics and photodynamic therapy. This is because the luminescence thermometry technique can accurately identify the temperature distribution in the molecular objectives or the biological body. Especially, the use of temperature-induced change in the luminescence intensity ratio (LIR) of two thermally coupled emission bands of lanthanide (Ln 3+ ) ions, embedded in some inorganic nanoparticles (NPs), allows temperature representing of a single living cell. In this review, we comprehensively summarized the concept of luminescence optical thermometry, photophysical properties of Ln 3+ ions, synthesis process, and various hosts doped with different Ln 3+ ions, in which they act as either sensitizers or activators. Selecting a proper host matrix is an efficient route to achieve the high performance of optical nanothermometers since it takes an important role in determining the luminescent efficiency. Initially, we defined and compared various classes of optical thermometers based on diverse spectroscopic parameters, such as emission intensity, band intensity ratio, bandwidth, band shape, polarization, spectral shift, and luminescence lifetime. Furthermore, we emphasized the most common approach for temperature monitoring, which is based on the thermally coupled levels (TCLs) of Ln 3+ ions, by exploiting the LIR technique, since it can provide a fast response with high accuracy, precision, and resolution. Additionally, this review also discusses the recent progress in diverse strategies to boost thermometric performances, such as changing dopants and utilizing various energy transfer mechanisms. Ultimately, we summed up the recent research achievements through analyzing the current research strategies, discussing future guidelines, as well as exploring the major difficulties for further advancement in the area.

Synthesis and luminescence properties of Er3+ doped and Er3+–Yb3+ codoped phosphovanadate YP0.5V0.5O4 phosphors

A series of Orthovanadate phosphate pure YP0.5V0.5O4, YP0.5V0.5O4 doped Er3+ and codoped Er3+/Yb3+ have been synthesized using a solid-state reaction. The samples were investigated by X-ray diffraction (XRD), infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) for detailed structural and morphological characterizations. The photoluminescence (PL) spectra were studied as a function of Er3+ concentration. The optimal Er3+ doping concentration in YP0.5V0.5O4 host was determined to be 2 mol%. The extinction phenomenon was correlated to the dipole - dipole (D - D) interactions. In the Er/Yb codoped YP0.5V0.5O4, the Er3+ green-red emission was intensified via the two-photon absorption process. Furthermore, the fluorescence intensity ratio (FIR) method was used to evaluate the optical temperature sensing parameters of the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 thermally coupled levels (TCL) over the 100–440 K range. The maximum values of Sa absolute and Sr relative sensitivity thermometric parameters were calculated to be 4.10−3 K−1 and 6.58%·K−1 respectively. The effects of the host composition by the presence of the phosphate (PO43−) and the vanadate (VO43−) entities were investigated on the Er3+ emissions and on the Er3+/Yb3+ optical thermometric parameters. YP0.5V0.5O4: Er3+, Er3+/Yb3+ prepared phosphors could be used for display and temperature sensing applications and to optimize the host effects on the luminescence and thermometric properties.

Effects of Sc3+ ions on local crystal structure and up-conversion luminescence of layered perovskite NaYTiO4: Yb3+/Er3+

This work focused on influences of Sc3+ dopants on local site symmetry and ligand field of Er3+ activators as well as its up-conversion luminescence performances sensitized by Yb3+ ions in NYTiO4 (NYT). The structure analysis and Judd-Ofelt calculation confirmed that doping Sc3+ ions could lower site symmetry as well changed the ligand field around Er3+ ions. The introduction of Sc3+ ions induced variations of crystal lattices, regulated distances between Er3+ions and Er3+ or Yb3+ ions, and thus influenced the up-conversion luminescence properties. Besides, time-resolved decay curves figured out the great enhancement of lifetime and luminescence quantum efficiency for both green and red emissions due to Sc3+ dopants. For optical temperature sensitivity, thermally coupled levels (TCLs) for blue emission 4F5/2/4F7/2→4I15/2 was studied for the first time. Besides, TCLs for violet emission 4G11/2/2H9/2→4I15/2 as well as green emission 2H11/2/4S3/2→4I15/2 were also recorded. By tri-doping Sc3+ ions into NYT: Yb/Er, both absolute sensitivity and relative sensitivity of above three TCLs were improved with temperature uncertainty decreasing.

Upconversion luminescence and optical temperature sensing characteristics of Er3+/Yb3+ codoped Na3Gd(PO4)2 phosphors

A new series of Yb3+/Er3+ ions co-doped Na3Gd (PO4)2 (NGPO) upconversion phosphors were synthesized by the solid-state method. The structural analyses indicate that all phosphors possess a single-phase monoclinic structure. Upon 980 ​nm excitation, with controlling the laser pump power, the emission color is tuned from yellow to greenish-yellow. We have also investigated the UC emissions thermal properties between 300 and 440 ​K, using a dual-mode temperature sensor based on fluorescence intensity ratio of thermally coupled levels (TCL) and non-thermally coupled levels (NTCL). The maximum absolute and relative sensitivities are calculated to be 14.07 10−3 ​K−1 ​at 440 ​K and 1.45% K−1 at 300 ​K respectively. Moreover, the heating effects produced by laser excitation were also measured. These results indicate that NGPO: Er3+/Yb3+ phosphors could be used for temperature sensing and optical heater applications.

Analogy of different optical temperature sensing techniques in LaNbO4:Er3+/Yb3+ phosphor

Three of the possible approaches to optical temperature sensing of a thermographic phosphor were formally compared in upconversion (UC) of Er3+ and Yb3+ doped lanthanum orthoniobate (LNO) phosphor. The three approaches used in the study were namely fluorescence intensity ratio (FIR) of thermally coupled levels (TCL), Valley to Peak ratio (VPR) and the ratio of non-thermally coupled levels (NTCL), respectively. The TCLs in the study were the ratio of intensities of 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 UC transitions of Er3+ ion. VPR method was verified within 2H9/2 → 4I15/2 transition of Er3+ UC. The other ratios of transitions which are not fit in TCL were investigated through NTCL technique. Ratios of several sets of transitions namely 4S3/2 → 4I15/2/2H9/2 → 4I15/2, 4S3/2 → 4I15/2/2I9/2 → 4I15/2, 4S3/2 → 4I15/2/4F9/2 → 4I15/2, 4F7/2 → 4I15/2/2H11/2 → 4I15/2, 2H11/2 → 4I15/2/4I9/2 → 4I15/2 and 2H11/2 → 4I15/2/2G11/2 were considered for NTCL technique. Moreover, the effect of temperature in the emission color was analyzed and a change from yellow (0.3310; 0.5990) to green (0.2590; 0.6740) was observed when the temperature rise has been increased from 14 to 300 K. Results obtained indicate that the LNO:Er3+/Yb3+ phosphor could be employed in optical thermometry and this phosphor would be a candidate with high potential as sensor operating from low to room temperature using TCL, VPR and/or NTCL methods. The most prominent sensing technique in the case of LNO:Er/Yb material among the three techniques is found to be NTCL with the high relative sensitivity of 1.19% K−1 at 300 K.

Photoluminescence properties of Er3+ and Eu3+ ions based on oxide host for optical temperature sensing with high sensitivity

Motivated from increasing demands of non-contact optical temperature sensing, the Yb3+-Er3+ and Eu3+ doped NaY9Si6O26 (NYS) oxide phosphors were designed by high-temperature solid-state reaction method. The phase purity of the as-prepared samples was checked from XRD patterns. For the upconversion luminescence in NYS:Yb3+,Er3+, the optimal Er3+ doping content was determined to be 1 mol%, and the characteristic emission peaks of Er3+ were observed in the region of 500–700 nm. In Eu3+ activated NYS phosphors, it has been found that the emissions originating in 5D1 and 5D0 levels demonstrate different change tendencies in intensity with Eu3+ doping concentration. By studying the temperature-dependent luminescent spectra, it was indicated that the emissions intensities from different excited states of Er3+ change differently with temperature. Two kinds of fluorescence intensity ratio (FIR) strategies were used in NYS:10%Yb3+,1%Er3+, containing thermally-coupled levels and non-thermally-coupled levels. In the NYS:3%Eu3+ phosphor, it was found that the FIR for 577 and 536 nm emissions follows a linear relation with temperature. The high sensitivities in the present phosphors indicate the potential application in optical temperature sensing.

Double nanocrystalline engineering for effective enhanced photoluminescence of Tb3+ in glass ceramic

Despite possessing good feature for optical thermometry, the rare (RE) ions-based temperature sensing (TS) has innate shortcoming of thermally coupled levels (TCLs) energy gap overlap, which reduces the sensitivity. In this work, a dual-luminous centers TS based on Tb3+ doped Cs4PbBr6 quantum dots (QDs) glass ceramic is fabricated. By locating in low phonon energy crystal field environment of Cs2ZnSi5O12 nanocrystalline (NS) and Cs4PbBr6 QDs, the emission intensity of Tb3+ can be enhanced by 14 times. The large exciton binding energy (420 meV) indicates that the prepared QDs glass ceramic has a good thermal stability and the PL intensity of Cs4PbBr6 QDs and Tb3+ can be well-maintained above 70% and 89% after 8 thermal cycles between 323K and 373K. Furthermore, the obtained maximum absolute sensitivity (Sa) and relative sensitivity (Sr) is as high as 0.2541 K-1 and 2.68% K−1, respectively. It is expected that the finding of this work can offer a help in exploring novel QDs/RE ions-based TS and further optimize their practical applications.

Optical thermometry based on thermolabile intrinsic polarons in Tm3+ and Yb3+ co-doped congruent lithium niobate single crystal

By contrast with the conventional optical thermometry based on fluorescence intensity ratio (FIR) of thermally coupled levels (TCLs), we propose a novel thermometry strategy based on the diversity in thermal responses of non-TCLs of Tm3+ (3H4→3H6/1G4→3F4). Notably, the exacerbated response-contrast stems from the intrinsic structure variation induced by thermolabile polarons of NbLi3+ and NbNb4+ in congruent Tm3+,Yb3+:LiNbO3(LN) single crystal. The luminescence mechanism incorporated with energy transfer processes associated with polarons levels is revealed by investigating the abnormal temperature dependence of emission spectra under 980 nm excitation. The maximum absolute (SA) and relative (SR) sensitivities reach as high as 3.7% K−1 and 1.25% K−1 at 80 K, much higher than those of the TCLs strategy based on thermally coupled Stark sublevels of Tm3+ (3H4|1→3H6/3H4|3→3H6) in Tm3+,Yb3+:LN. This study demonstrates an effective pathway for developing new FIR strategies with improved sensitivities via taking advantage of host structure variation.

Multiple ratiometric nanothermometry operating with Stark thermally and non-thermally-coupled levels in upconverting Y2−xMoO6:xEr3+ nanoparticles

Contactless optical nanothermometers of high thermal sensitivity are in great demand in various fields. In this work, we applied a facile sol-gel method to synthesize a series of Y2-xMoO6:xEr3+ upconverting nanoparticles (UCNPs), capable of acting as luminescence nanothermometers. Upon 980 nm laser light irradiation, with increasing Er3+ content, the prepared samples show a color-tunable upconversion emission, from green to yellow. Comparison of the thermometric properties determined by the Stark thermally coupled levels (TCLs) with those determined by the Stark non-thermally coupled levels (non-TCLs) showed that the superior thermal sensitivity (maximal Sr = 2.063%K−1 at 303 K) is achieved for the non-TCLs 4F9/2(1)/4S3/2(1). Moreover, a higher content of Er3+ in UCNPs (Y1.88MoO6:0.12Er3+ UCNPs) has been found to lead to a significant increase of Sr (Sr MAX = 2.460%K−1 at 303 K). Y2-xMoO6:xEr3+ UCNPs are promising materials for contactless nanothermometers of high sensitivity.

Eu3+-doped ratiometric optical thermometers: Experiment and Judd-Ofelt modelling

Rare earth-doped materials are successfully utilized as non-contact optical temperature sensors. Thermal sensing is usually based on the ratiometric technique between two separate emission lines originated from thermally-coupled levels. We study Gd 2 O 3 :Eu 3+ 1 at.% and YAG: Eu 3+ 4 at.% phosphors as luminescence thermometers in 298–473 K range using both conventional experimental and Judd-Ofelt based theoretical approaches. Thermometric performances of suggested sensors were quantified through absolute and relative thermal sensitivities and temperature resolution. Experiment and theoretical modelling gave similar results. This proves the theoretical model as a simple and fast method for estimation of the Eu 3+ -doped thermometer perspectives. • Eu 3+ -doped phosphors were synthesized via different modified Pechini methods. • Gd 2 O 3 :Eu 3+ and YAG:Eu 3+ nanopowders were used as contactless luminescence thermometers. • Thermometric performances were estimated through thermal sensitivities and temperature resolution. • Experimental approach and Judd-Ofelt based theoretical model give similar results.