Upconversion Emission Bands Research Articles

Upconversion enhancement and temperature sensing studies in Li+ ions incorporated GdPO4:Tm3+/Yb3+ phosphor

The GdPO4:Tm3+/Yb3+ phosphor codoped with various concentrations of Li + ions were synthesized for upconversion emission and optical thermometry studies. Excitation using 980 nm laser diode results in three upconversion (UC) emission bands with centre wavelengths of 478, 648 and 692 nm. These bands are originated from 1G4→3H6, 1G4→3F4, and 3F3→3H6 transitions of the Tm3+ ion, respectively. Li+ ions modified the local crystal symmetry around dopant ions, resulting enhanced UC emissions. The lifetime of the 1G4 level of Tm3+ ion was studied using a 980 nm laser excitation. The temperature sensing performances of GdPO4:Tm3+/Yb3+ and GdPO4:Tm3+/Yb3+/Li+ based on fluorescence intensity ratio (FIR) technique were evaluated in the temperature range 301–713 K under 980 nm excitation. Non-thermally coupled levels 3F3 (692 nm) and 1G4 (478, 648 nm) were utilized for FIR estimation. A maximum absolute sensitivity of 6.28 × 10−3 K−1 at 653 K and 18.71 × 10−3 K−1 at 713 K were observed for Li + undoped and codoped phosphors respectively. The result indicates that codoping of Li + ions improved the UC emission as well as optical thermometry. Moreover, CIE colour coordinates and anti-counterfeiting application were also exhibited.

BaMoO4:Nd3+-Yb3+ upconverting phosphors for NIR to NIR contactless temperature reading out

BaMoO4:Nd3+–Yb3+ phosphors have been synthesized by using conventional solid state reaction synthesis technique. Frequency up-conversion (UC) emission studies have been performed under 980 nm excitation. The developed UC phosphors show multicolor upconverted emission bands in the 400–900 nm wavelength range and assigned via the radiative transitions of Nd3+ ion. FIR technique based on frequency upconversion has been applied for the 4F7/2→4I9/2 and 4F5/2→4I9/2 transitions of Nd3+ ion in the NIR (750–804 nm) region arising from the two thermally coupled energy states. The energy gap (ΔE) between the upper and lower excited levels (4F7/2 and 4F5/2) was found to be ∼ 800 cm−1. The maximum sensor sensitivity ∼ 23.2 × 10−4 K−1 at 306 K (operating temperature range 306–483 K) under 980 nm NIR laser irradiation for BaMoO4:Nd3+-Yb3+ phosphors is reported. The prepared phosphors have proven their utility as a novel upconverting material for NIR to NIR contactless temperature reading out.

Visible to infrared wide wavelength range luminescence of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor under 808/980 nm excitation and temperature sensing application

Here, the Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphors are prepared through solid-state route. The upconversion (UC)/downshifting (DS) luminescence and temperature performances of all samples are investigated in detail. Under 808 nm excitation, the infrared emission band (∼2000 nm) of Ho3+ ions is obtained. Especially, the energy transfer process of Nd3+ → Yb3+ → Ho3+ has increased the emission intensity of ∼2000 nm. Moreover, the infrared emission band presents thermal enhancement. Under 980 nm excitation, the UC emission band 500–960 nm is investigated. The green and red light of Ho3+ ion, near infrared light of Nd3+ ions are achieved. In addition, the possible luminescence mechanism of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor is discussed. At last, the optical temperature sensing characteristics of the phosphor are studied according to the luminescence intensity ratio (LIR) technology. The maximum relative sensitivity of Sr2LaNbO6: Yb3+/Nd3+/Ho3+ reaches 5.476 % K−1 at 293 K. These results prove that the Sr2LaNbO6: Yb3+/Nd3+/Ho3+ phosphor presents the luminescence in infrared and visible range. The Sr2LaNbO6:Yb3+/Nd3+/Ho3+ phosphor also can be applied to design optical temperature sensor.

Up-Conversion Emissions from HfO2: Er3+, Yb3+ Nanoparticles Synthesized by the Hydrothermal Method.

Up-conversion emission from HfO2 nanoparticles, as a host lattice, doped with Er3+ and Yb3+ ions and codoped with alkaline cations Li+ and Na+ obtained. The HfO2 nanoparticles, about 80 nm in diameter, were synthesized by the hydrothermal method at 200 °C for 1.3 h, and an additional heat treatment at 1000 °C was necessary to ensure the dopants incorporation into the host lattice. These nanoparticles were studied by means of XRD, Raman Spectroscopy, SEM, EDS, PL, CL, and up-conversion luminescence. First, the doping was performed with Er3+ ions in different percentages. The photoluminescence and cathodoluminescence studies showed an inefficient emission, and only at 7 at % Er3+ ions, the sample presented emissions at 522, 545, and 656 nm corresponding to the transitions of the Er3+ ions. So, codoping was carried out, and HfO2: Er3+/Yb3+ generated an efficient conversion process. The atom percentage of Yb3+ ions was fixed (7 at % Yb3+), and the Er3+ content was varied, showing the highest emission intensity at 3 at % Er3+ ions. Subsequently, the up-conversion emission intensity was optimized by varying the percentage of Yb3+ ions and keeping the Er3+ ion content fixed (3 at %). Adding cations such as Na+ and Li+ in different percentages, a notable improvement of the up-conversion emission intensities in the HfO2: Er3+/Yb3+ nanoparticles was obtained. The up-conversion emission bands observed were located at ∼523 and 544 nm, corresponding to the electronic transitions 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2, respectively. While the bands at ∼652 and 673 nm correspond to the transition 4F9/2 → 4I15/2, respectively. The excitation of these materials with infrared radiation (980 nm) produced noticeable emission bands in the red spectral range, whereas excitation with accelerated electrons (CL) generated prominent bands in the green region.

Na5Y9F32:Yb3+/Ho3+/Tm3+ up-conversion luminescent single crystals for highly sensitive optical temperature sensor

A novel non-contact optical temperature sensor with excellent performance of its adequate temperature resolution (δ(T) = 0.017 K) and exceptional relative thermal sensitivity (Sr = 1.97% K−1) was developed based on the up-conversion fluorescence intensity ratio (FIR) of Ho3+/Tm3+/Yb3+ triply incorporated Na5Y9F32 single crystal grown by Bridgman method. The up-conversion (UC) emission bands at 482 nm/669 nm/700 nm of Tm3+ and 522 nm/542 nm/653 nm of Ho3+ ions were observed upon excitation of 980 nm. The effects of Yb3+ concentration from 0.5 to 4 mol% on the UC emission of the Ho3+/ Tm3+ fixed doped Na5Y9F32 single crystal were also carried out. It has been demonstrated through the calculation of the steady-state rate equation that the intensity of UC emission is linearly heightened with the pump power, confirming the conversion mechanism. The temperature sensing performance of the Ho3+/Tm3+/Yb3+ incorporated Na5Y9F32 single crystals was explored by analyzing the FIR employing thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs). The maximum values of absolute sensitivity (Sa) and relative sensitivity (Sr) of the material are estimated to be 19.1% K−1 (323 K) and 1.97% K−1 (398 K), separately, which are far higher than those of previously reported RE3+-doped UC optical temperature sensor materials. This study shows that the transparent single crystal has the great potential as a non-contact optical thermometer, and provides a new idea for studying other highly optical sensing materials.

Highly efficient upconversion luminescence in narrow-bandgap Y2Mo4O15.

Lanthanide-doped upconversion (UC) materials have been extensively investigated for their unique capability to convert low-energy excitation into high-energy emission. Contrary to previous reports suggesting that efficient UC luminescence (UCL) is exclusively observed in materials with a wide bandgap, we have discovered in this study that Y2Mo4O15:Yb3+/Tm3+ microcrystals, a narrowband material, exhibit highly efficient UC emission. Remarkably, these microcrystals do not display any four- or five-photon UC emission bands. This particular optical phenomenon is independent of the variation in doping ion concentration, temperature, phonon energy, and excitation power density. Combining theoretical calculations and experimental results, we attribute the vanishing emission bands to the strong interaction between the bandgap of the Y2Mo4O15 host matrix (3.37 eV) and the high-energy levels (1I6 and 1D2) of Tm3+ ions. This interaction can effectively catalyze the UC emission process of Tm3+ ions, which leads to Y2Mo4O15:Yb3+/Tm3+ microcrystals possessing very strong UCL intensity. The brightness of these microcrystals outshines commercial UC NaYF4:Yb3+,Er3+ green phosphors by a factor of 10 and is 1.4 times greater than that of UC NaYF4:Yb3+,Tm3+ blue phosphors. Ultimately, Y2Mo4O15:Yb3+/Tm3+ microcrystals, with their distinctive optical characteristics, are being tailored for sophisticated anti-counterfeiting and information encryption applications.

Improvement of upconversion and temperature sensing properties in Ho3+/Yb3+ co-doped Ca0.5Gd(WO4)2 phosphor via incorporation of Bi3+

A series of Ca0.5Gd(WO4)2: Ho3+/Yb3+/Bi3+ phosphors prepared by solid-state reaction method were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), elemental mapping, upconversion (UC) spectroscopy and decay time analysis. Under 980 nm excitation, four up-converted emission bands of Ho3+ were observed in all samples. The concentration quenching effect of the UC emission appears by changing the concentration of Ho3+ in Ca0.5Gd(WO4)2: x mol% Ho3+, 40 mol% Yb3+ and Yb3+ in Ca0.5Gd(WO4)2: 1 mol% Ho3+, y mol% Yb3+, and the optimal concentration of Ho3+ and Yb3+ were determined to be 1 and 40 mol%, respectively. Compared to Bi3+-absent sample, the upconversion luminescence (UCL) intensities of green emission (540 nm) and red emission (644 nm) in Ca0.5Gd(WO4)2: 1 mol% Ho3+, 40 mol% Yb3+ via 15 mol% Bi3+ doping were increased by 2.5 and 3.6 times, respectively. The involved UCL mechanism based on the power dependent UC emission spectra were analyzed in detail. Additionally, the temperature sensing performances based on non-thermally coupled levels (NTCLs) 5F4(5S2) → 5I8, and 5F5 → 5I8 of Ho3+ ions and thermal quenching properties of the samples were also investigated in the range of 298–573 K. The maximum relative sensitivity (SR) of Ca0.5Gd(WO4)2: 1 mol% Ho3+, 40 mol% Yb3+ and Ca0.5Gd(WO4)2: 1 mol% Ho3+, 40 mol% Yb3+, 15mol% Bi3+ reached 0.0094 K-1 and 0.0112 K−1 at 298 K, respectively. The results indicated that doping Bi3+ ions can enhance the UCL intensity and optical temperature sensing of Ca0.5Gd(WO4)2: Ho3+/Yb3+.

Efficient upconversion and downshifting luminescence of CaIn2O4: Yb3+/Tm3+/RE3+ (RE=Er/Ho) phosphor: Temperature sensing performance in the visible and near-infrared range

In this paper, the upconversion(UC) and downshifting(DS) luminescence and thermal sensing performances of the CaIn2O4: RE3+/Tm3+/Yb3+(RE=Er, Ho) phosphors are investigated in detail. The bright UC emission bands from 450 to 900 nm and the DS luminescence bands from 1000 to 1700 nm are obtained under 980 nm excitation. The typical near infrared(NIR) emisson band(∼1550 nm) of Er3+ ions and the NIR emission band(∼1200 nm) of Ho3+ ions are gained. The temperature sensing features of CaIn2O4: RE3+/Tm3+/Yb3+ (RE=Er, Ho) phosphors are investigated with the luminescence intensity ratio (LIR) technique. The results indicate that the maximum relative sensitivity (SRmax) of CaIn2O4: Er3+/Tm3+/Yb3+ sample reaches 1.576% K-1 at 313 K, and the SRmax of CaIn2O4: Ho3+/Tm3+/Yb3+ sample reaches 0.797% K-1 at 353 K in UC range. In addition, the higher temperature measuring sensitivities have been obtained in NIR-II region with the DS luminescence of CaIn2O4: RE3+/Tm3+/Yb3+ phosphors. The above results indicate that the CaIn2O4: RE3+/Tm3+/Yb3+ phosphors show bright emission bands in visible and NIR-II, and higher sensitivity for temperature measurement. The CaIn2O4: RE3+/Tm3+/Yb3+ phosphors present great application in optical temperature measurement.

Method for separating spectrally overlapping multiphoton upconverted emission bands through spectral power dependence analysis

Method for separating spectrally overlapping multiphoton upconverted emission bands through spectral power dependence analysis

Upconversion properties of Er, Yb co-doped KBi(MoO4)2 nanomaterials for optical thermometry

Rare earth ions doped upconversion materials have an extensive range of utilizations because of their exceptional luminescence properties. Here, scheelite type Yb3+, Er3+ co-doped KBi(MoO4)2 nanomaterials were produced by means of a conventional co-precipitation method at room temperature with a typical crystallite size of 13 nm. 980 nm excitation aided in the investigation of the concentration and power-dependent upconversion emission. The optimum upconversion emission is obtained with Er and Yb concentrations of 0.035 and 0.125 mol%, respectively in KBi(MoO4)2 nanomaterials. The intensity ratio of upconversion emission bands based on 529 and 551 nm is investigated in the temperature range of 200–550 K and the theoretical function is used for fitting the exploratory information. The absolute sensitivity is found to be of maximum value of 0.0123 K-1, indicating that this double molybdate can be utilized as a potential probe for luminescence-based temperature sensing.

Upconversion Luminescence through Cooperative and Energy-Transfer Mechanisms in Yb3+ -Metal-Organic Frameworks.

Lanthanide-doped metal-organic frameworks (Ln-MOFs) have versatile luminescence properties, however it is challenging to achieve lanthanide-based upconversion luminescence in these materials. Here, 1,3,5-benzenetricarboxylic acid (BTC) and trivalent Yb3+ ions were used to generate crystalline Yb-BTC MOF 1D-microrods with upconversion luminescence under near infrared excitation via cooperative luminescence. Subsequently, the Yb-BTC MOFs were doped with a variety of different lanthanides to evaluate the potential for Yb3+ -based upconversion and energy transfer. Yb-BTC MOFs doped with Er3+ , Ho3+ , Tb3+ , and Eu3+ ions exhibit both the cooperative luminescence from Yb3+ and the characteristic emission bands of these ions under 980 nm irradiation. In contrast, only the 497 nm upconversion emission band from Yb3+ is observed in the MOFs doped with Tm3+ , Pr3+ , Sm3+ , and Dy3+ . The effects of different dopants on the efficiency of cooperative luminescence were established and will provide guidance for the exploitation of Ln-MOFs exhibiting upconversion.

Upconversion Luminescence through Cooperative and Energy‐Transfer Mechanisms in Yb3+‐Metal‐Organic Frameworks

AbstractLanthanide‐doped metal–organic frameworks (Ln‐MOFs) have versatile luminescence properties, however it is challenging to achieve lanthanide‐based upconversion luminescence in these materials. Here, 1,3,5‐benzenetricarboxylic acid (BTC) and trivalent Yb3+ ions were used to generate crystalline Yb‐BTC MOF 1D‐microrods with upconversion luminescence under near infrared excitation via cooperative luminescence. Subsequently, the Yb‐BTC MOFs were doped with a variety of different lanthanides to evaluate the potential for Yb3+‐based upconversion and energy transfer. Yb‐BTC MOFs doped with Er3+, Ho3+, Tb3+, and Eu3+ ions exhibit both the cooperative luminescence from Yb3+ and the characteristic emission bands of these ions under 980 nm irradiation. In contrast, only the 497 nm upconversion emission band from Yb3+ is observed in the MOFs doped with Tm3+, Pr3+, Sm3+, and Dy3+. The effects of different dopants on the efficiency of cooperative luminescence were established and will provide guidance for the exploitation of Ln‐MOFs exhibiting upconversion.

Tailoring luminescent patterns with rare-earth photonic materials for anti-counterfeiting applications: A lightkey

Anti-counterfeiting strategies are competitively developed against fast-growing counterfeit markets as a cornerstone for the next generation of luminescent security inks, so it will be more difficult to mimic by ever increasing sophisticated counterfeiters. In particular, rare-earth doped up-conversion luminescent materials present important advantages such as invisibility in ambient light, excitation by low cost NIR irradiation, lack in background noise and negligible auto-fluorescence from the surface. Here we present colour tuneable up-conversion emissions in two families of rare-earth doped photonic materials (sol-gel derived nano-glass-ceramics and glasses prepared by melt quenching technique) for tailoring the overall emitted luminescence, as a sort of “lightkey”. In particular, intensity ratios among UV and VIS up-conversion emission bands can be tuned by modifying doping concentration level and excitation power density, as an additional security feature itself, giving rise to a multi-digit security code based on light-responsive encrypted patterns.

Growth, structure and upconversion properties of Yb3+ and Er3+ co-doped Gd3Sc2Al3O12 crystal

Upconversion luminescent materials exhibit excellent near-infrared to visible conversion properties that make them crucial for optoelectronics, visible display devices, and biological labels. Herein, we report a high-quality Yb3+ and Er3+ co-doped Gd3Sc2Al3O12(GSAG) single crystal which was grown successfully by the traditional Czochralski method with Er3+ and Yb3+ doping concentration of 1 at.% and 10 at.%, respectively. The structure parameters of the crystal were observed by the X-ray Rietveld refinement method. In addition, the transmission and upconversion emission properties of the crystal were analyzed at room temperature. The 940 nm excited upconversion energy transfer mechanism and dependence of the green-to-red upconversion intensity ratio (Ig/r) on pump power were investigated. A dominant two-photon absorption process of the green and red upconversion emission bands were revealed in Yb,Er:GSAG crystal. The results indicate the crystal is a promising upconversion single crystalline material.

Effect of pH on Structure and Green Emission of Er/Yb/Mo Tri-doped Hydroxyapatite

This paper reported the impact of pH on the structure, morphology, and the green upconversion (UC) emission of Er/Yb/Mo tri-doped hydroxyapatite (HA) synthesized through hydrothermal method. X-ray diffraction confirmed that the pH of the solution strongly influenced the phase composition of the phosphors, and HA single phase was obtained at a high pH value. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the phosphor exhibited rod-like morphology, and their length increased with increased of the pH values. Under laser-diode excitation wavelength of 975 nm, the phosphor showed typical upconversion emission bands of the ion: strong green emission bands around 510-535/540-560 nm and weak red emission bands around 630-680 nm. The green and red emission intensity as a function of pH reached its maximum value at pH8. Finally, the emission intensity of

Thermal sensing in NIR to visible upconversion of Ho3+ and Yb3+ doped yttrium oxyfluoride phosphor

Rare-earth (RE) oxyfluorides compatible for RE doping make a path for efficient near-infrared (NIR) to visible upconversion (UC). This paper describes the efficient use of YOF:Ho3+/Yb3+ phosphor nanoparticles synthesised by the Pechini sol-gel method as thermal sensors using UC in the visible region. Material characterisations such as X-ray diffraction, Raman spectroscopy and scanning electron microscopy (SEM), revealed the structural information of the material and its prominence for RE doping. Average size of 44 nm obtained from SEM with maximum phonon energy of 480 cm−1 observed from Raman measurements assure the use of RE doped YOF for UC. Excitation of YOF:Ho3+/Yb3+ with NIR (980 nm) revealed intense UC emission in the visible and DS in the NIR region. Although Ho3+ and Yb3+ ions do not have resonance energy levels at 980 nm, three two-photon UC emission bands centred at 538, 655 and 755 nm from 5F4+5S2→5I8, (5F5→5I8+5F3→5I7) and 5F4+5S2→5I7 transitions were obtained through phonon-assisted energy transfer. For the evaluation of thermal sensitivities using 980 nm excitation, fluorescence intensity ratio (FIR) was used based on the thermally non-coupled levels in the visible UC bands between the temperatures 20–300 K. The relative sensitivities (SR) which is the measure of temperature sensing ability of YOF materials with 1 mol % Ho3+ and 10 mol % Yb3+ was found to be 0.32 for UC in visible region was achieved with 980 nm excitation at 300 K.

Bi-functional nanocomposite based on phosphor and carbon nanotubes for tumor ablation in a photothermal fiber system with temperature feedback

Photothermal therapy has aroused tremendous attention in the biomedical field as a promising and less-invasive method for tumor ablation, but its development is greatly limited due to lack of efficient and controllable photothermal materials in treatment. Here, a dual-functional composite based on lanthanide-doped nanoparticles and carbon nanotubes has been successfully synthesized for designing the photothermal system. Under near-infrared laser excitation, the composite could effectively convert light energy into thermal energy due to non-radiation relaxation of nanoparticles and carbon nanotubes. More importantly, the optical thermometer was constructed through the luminescence intensity ratio of different upconversion emission bands corresponding to the lanthanide ions in the nanophosphors. Furthermore, we established an optical fiber system with the developed composite for precise tumor treatment. This work verified the feasibility of accurate temperature monitoring and efficient optical heating under near-infrared laser excitation, proposed a design of multifunctional photothermal materials for tumor treatment with the unique advantages of high accuracy and low invasive burden.

Down- and up-conversion processes in Nd3+/Yb3+ co-doped sodium calcium silicate glasses with concomitant Yb2+ assessment

Novel Nd3+/Yb3+ co-doped sodium calcium silicate glasses were prepared by melting quenching method. Spectroscopic study was carried out as a function of doping content by fixing sensitizer (Nd3+) concentration to 0.2 mol% and adjusting activator (Yb3+) from 0 to 1.0 mol%. The energy transfer (ET) mechanisms between Nd3+ and Yb3+ are discussed based on their energy levels and excitation power-dependence emission intensity. Results show that the presence of Yb2+ might be considered for the Nd3+-free and co-doped samples. The ET was confirmed by the down-conversion NIR emission spectra of the doped and co-doped samples under excitation at 808 nm. The mechanisms observed seem to involve only one VIS absorbed photon for each NIR emitted via direct energy transfer between 4F3/2 of Nd2+ and 2F5/2 of Yb3+ compensated by phonon assistance due to energy gap between these levels. The efficiency of ET increases with the ytterbium content up to almost 90% for the sample with 1 mol% of Yb2O3, which was evaluated by lifetime measurements. Up-conversion photoluminescence by exciting trivalent ions of neodymium (808 nm) and ytterbium (975 nm) is reported. The observed up-converted emission bands are related to the 4f-4f transitions of Nd3+ and the spin-forbidden 5d-4f transition of Yb2+. Nd3+ up-conversion emission is observed under 975 nm excitation, presenting an almost quadratic emission dependence with power excitation, which suggests that two laser photons participate in the up-conversion (UC) process, showing that ET occurs by a phonon-assisted energy transfer and cooperative energy transfer.

Yb3+/Mn2+ co-doped Y3Al5O12 phosphors for optical thermometric application

Yb3+/Mn2+ co-doped Y3Al5O12 phosphors are prepared by the high-temperature solid-phase reaction via sintering the raw materials at 1600 °C in reducing atmosphere. Orange-red up-conversion (UC) emission of Mn2+ was observed at room temperature. Under the 980 nm excitation, the orange UC emission band peaked at 585 nm was realized, which came from the 4T1(4G) → 6A1(S) transition of cooperative luminescence of Yb3+-Mn2+ dimers. Due to rapid decrease of the UC emission intensity with increasing temperature, high absolute sensitivity (Sa) and relative sensitivity (Sr) were obtained. The maximum value of Sa is 0.017 K−1 at 423 K, and the maximum value of Sr is 3.4% K⁻1 at 423 K. All the Sr value were over 1.7% K−1 in the range from 298 K to 423 K. The thermal reliability was 95.2% at 423 K and 96.9% at 298 K, respectively. In summary, YAG:Yb3+, Mn2+ can be a reliable candidate for optical temperature sensing.

Tm3+,Yb3+: Y2SiO5 up-conversion phosphors: Exploration of temperature sensing performance by monitoring the luminescence emission

Tm3+,Yb3+:Y2SiO5 ceramic powders synthesized via combustion route exhibited up-conversion (UC) fluorescence when were submitted to CW-laser radiation at 980 nm. Four emission bands at 478 nm, 650 nm 690 nm and 798 nm, corresponding to transitions 1G4→3H6, 1G4→3F4, 3F2,3 → 3H6 and 3H4→3H6 were observed. The properties of the UC emission bands are influenced by temperature. Thermal coupling levels (TCL) cause a noticeable change in the relative intensities between the excited states 3F2,3 → 3H6 and 3H4→3H6 in the temperature range of 298–473 K. The maximum absolute sensitivity (1.25 × 10−3 K-1, 473 K) and relative sensitivity (1.83% K−1, 298 K) were obtained using the fluorescence intensity ratio (FIR) technique. Thermal sensing performance has been explored by utilizing the FIR technique between non-thermally coupled levels (NTCL). Through the calculation of FIR of NTCL1G4→3H6 and 3H4→3H6, the value of the relative sensitivity was acquired (1.5% K−1, 298 K). The comparison of TCL and NTCL FIR-method performances shows that this ceramic powder has the potential to be used as a ratiometric thermal sensor for remote temperature measurements.