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In recent years, phosphors have been used in the field of temperature sensing, which has aroused great interest because of its advantages of quick response, high sensitivity and high accuracy. However, exploring optical thermometers with ultra-high sensitivity remains a challenge. In this work, we have designed and synthesized Sm3+ and Mn4+ co-doped La 3 Mg 2 NbO 9 phosphor for temperature sensing for the first time by utilizing the anomalous thermal quenching property of Sm3+ ions and the sensitive thermal quenching property of Mn4+ ions. Furthermore, the structure, elemental distribution, morphology and optical characteristics of La 3 Mg 2 NbO 9 :Sm3+,Mn4+ were studied in detail. Benefiting from the different responses of the Sm3+ and Mn4+ ions to temperature, the fluorescence intensity ratios of Sm3+ to Mn4+ in La 3 Mg 2 NbO 9 samples show excellent optical thermometry performance in the range of 303–463 K. The maximum absolute sensitivity (S a) and relative sensitivity (S r) values of La 3 Mg 2 NbO 9 :Sm3+,Mn4+ sample reach as high as 0.117 K-1 (@463 K) and 4.48 % K−1 (@303 K), respectively. Furthermore, the maximum of S a is 0.385 K−1 (@463 K) and the maximum of S r is 4.54 % K−1 (@303 K) based on the fluorescence lifetime temperature measurement method. The temperature cyclotron curve of the sample proves that the sample has excellent stability and repeatability in temperature measurement. These results demonstrate that the designed La 3 Mg 2 NbO 9 :Sm3+,Mn4+ phosphor is promising for the field of non-contact optical temperature thermometry. [ABSTRACT FROM AUTHOR]

Due to its relatively low cost and remote detection characteristics, optical temperature sensing technology based on FIR has received widespread attention. At present, there is a lack of theoretical guidance on how to purposefully improve or guide the development of high-performance temperature sensing materials. Herein, the structure of a novel material K 7 MgSc 2 B 15 O 30 has been confirmed by the XRD analysis. Furthermore, the effect of Zn on the crystal structure and the photoluminescence (PL) properties of K 7 MgSc 2 B 15 O 30 :Mn2+ has been studied. The PL spectra analysis of a series of Mn2+ doped K 7 MgSc 2 B 15 O 30 luminescence materials indicates that two kinds of Mn2+ emitting centers (Mn(1) and Mn(2)) exist due to the two possible substitution sites Mg2+ and Sc3+. With the increasing of Zn2+, the intensity ratio of Mn(2) to Mn(1) improves from 1.01 to 1.88 at room temperature. Especially, the thermal stability of Mn(1) and Mn(2) gradually decrease with the increasing of Zn2+ contents, which can be due to the lengthening of Zn/Mg–O bonds and the lattice distortion of ScO 6 , respectively. Finally, their temperature sensing sensitivity has been enhanced by the doping of Zn2+, which has a close relation to the different effect of the thermal stability of Mn(1) and Mn(2). This work is expected to provide new ideas for the development of high-performance temperature sensing materials based on FIR, and is helpful to understand the relationship between the crystal structure and luminescence properties. • The crystal structure of K 7 MgSc 2 B 15 O 30 has been firstly studied. • Two emitting centers of Mn have been confirmed in K 7 MgSc 2 B 15 O 30 :Mn2+. • The decreased PL thermal stability attributes to the structure modulation. • The relative sensitivity can been tunable by the doping of Zn2+. [ABSTRACT FROM AUTHOR]

In the quest of finding the minimum ceria doping for a stabilized zirconia matrix, we report a remarkable structure–property correlation for a high (> 99%) density, fine grained (∼100 nm), fully phase‐pure (confirmed via both slow scan X‐ray diffraction and Raman spectroscopy) tetragonal 10 mol.% CeO2‐doped zirconia ceramics (10Ce‐TZP). A starting near spherical, ultrafine (∼7 nm) powders with high surface area (∼170 m2/g) ensured the conventional pressureless sintering at 1150°C without the need of any additives, binders, and/or sintering aid to achieve this high density. No monoclinic phase was traced at the end of the low‐temperature degradation test for 100 h in boiling water; negligible (∼5% monoclinic phase) amounts showed up in the thermal quenching tests. The sintered 10Ce‐TZP ceramic recorded comparable/better hardness and indentation toughness value with respect to higher (i.e., 12 mol.%) ceria doped‐zirconia systems. For the first time, nanograined translucent 10Ce‐TZP ceramic portrayed a remarkable transmittance of ∼38% at 600 nm wavelength for 0.6 mm thick pellet. [ABSTRACT FROM AUTHOR]

The anomalous luminescence thermal quenching performance caused by negative thermal expansion has attracted much attention due to the potential application in optical fields. However, the downshifting emissions with abnormal thermal quenching achieved by isotropic negative thermal expansion for optical temperature sensing applications are still lacking. Herein, a large enhancement of red emission and a high temperature sensing performance are realized by isotropic negative thermal expansion in ScF 3 :Tb3+/Eu3+ phosphors ceramics. Specially, a selectively thermal enhanced red emission of Eu3+ from 5D 0 →7F 2 with hypersensitive transition characteristics could be obtained due to the thermal stimulated lattice distortion. Attributing to the shortening of cation spacing, the energy transfer efficiency between Tb3+ and Eu3+ is largely enhanced with the increasing of the temperature from 303 to 473 K. The enhanced energy transfer leads to that the emission of Tb3+ firstly increases and then slightly decreases, whereas the emission from Eu3+ has been largely improved. Finally, an optical temperature sensing strategy based on the fluorescence intensity ratio of the sensitizer Tb3+ (signal ions) and the activator Eu3+ (referring ions) is designed, attributing to the distinguishable luminescence response to the temperature. The obtained maximum relative sensitivity is 1.04 % K−1 (@303 K). Besides, the sensing strategy based on lifetime mode also suggests a maximum relative sensitivity of 1.00 % K−1 at 343 K. It provides a feasible strategy to obtain an optical temperature sensing material with high emission efficiency at a high temperature, which sheds light on the design of luminescence materials keeping high luminescence stability in a wide temperature range in the fields of optical temperature sensing. [ABSTRACT FROM AUTHOR]

Applications of luminescence at high temperature such as high‐power lighting, lasing, thermophotovoltaics, and photonic coding, are severely prevented due to the notorious thermal quenching (TQ). Although anti‐TQ luminescence (anti‐TQL) is reported using highly oxygen‐coordinated solid‐state oxide as host in virtue of the rigid skeleton that resists lattice vibration at elevated temperatures, it is meaningful to extend anti‐TQL to other hosts. Herein, taking advantage of the ligand‐metal antenna effect and the negative thermal expansion feature of Eu3+ doped MIL‐68‐In (MIL‐68‐In/xEu), adjustable anti‐TQL is realized for the first time, that is, anti‐TQ, zero‐TQ, and TQ at x = 5%, 10%, and 50%, respectively. Therefore, except for added novel mechanisms, this work has also expanded the hosts available for high‐temperature luminescence and enabled advanced photonic coding in terms of facial synthesis, rich information, and visual changes of emission intensity instead of device‐dependent analogous. [ABSTRACT FROM AUTHOR]

ZnAl2O4 with a typical spinel structure is highly expected to be a novel rare‐earth‐free ion‐activated oxide phosphor with red emission, which holds high actual meaning for advancing phosphor‐converted light‐emitting diode (pc‐LED) lighting. Among the rare‐earth‐free activators, Mn4+ ions have emerged as one of the most promising activators. Considering the price advantage of MnCO3 generating Mn2+ ions and the charge compensation effect potentially obtaining Mn4+ ions from Mn2+ ions, this research delves into a collection of ZnAl2O4:Mn2+(Mn4+), x Li+ (x = 0%–40%) phosphors with Li+ as co‐dopant and MnCO3 as Mn2+ dopant source prepared by a high temperature solid‐state reaction method. The lattice structure was investigated using X‐ray diffraction (XRD), photoluminescence (PL), and photoluminescence excitation (PLE) spectroscopy. Results suggest a relatively high probability of Li+ ions occupying Zn2+ lattice sites. Furthermore, Li+ ion doping was assuredly found to facilitate the oxidization of Mn2+ to Mn4+, leading to a shift of luminescence peak from 516 to 656 nm. An intriguing phenomenon that the emission color changed with the Li+ doping content was also observed. Meanwhile, the luminescence intensity and quantum yield (QY) at different temperatures, as well as the relevant thermal quenching mechanism, were determined and elucidated detailedly. [ABSTRACT FROM AUTHOR]

X‐ray scintillators have gained significant attention in medical diagnostics and industrial applications. Despite their widespread utility, scintillator development faces a significant hurdle when exposed to elevated temperatures, as it usually results in reduced scintillation efficiency and diminished luminescence output. Here we report a molecular design strategy based on a hybrid perovskite (TpyBiCl5) that overcomes thermal quenching through multi‐excited state switching. The structure of perovskite provides a platform to modulate the luminescence centers. The rigid framework constructed by this perovskite structure stabilized its triplet states, resulting in TpyBiCl5 exhibiting an approximately 12 times higher (45 % vs. 3.8 %) photoluminescence quantum yield of room temperature phosphorescence than that of its organic ligand (Tpy). Most importantly, the interactions between the components of this perovskite enable the mixing of different excited states, which has been revealed by experimental and theoretical investigations. The TpyBiCl5 scintillator exhibits a detection limit of 38.92 nGy s−1 at 213 K and a detection limit of 196.31 nGy s−1 at 353 K through scintillation mode switching between thermally activated delayed fluorescence and phosphorescence. This work opens up the possibility of solving the thermal quenching in X‐ray scintillators by tuning different excited states. [ABSTRACT FROM AUTHOR]

A series of Eu3+ doped Sr2GdTaO6 (SGT) phosphors with double perovskite structure were synthesized via a high-temperature solid-state reaction approach. The crystal structure, morphology and luminescence properties were characterized by means of X-ray diffraction, transmission electron microscope, luminescence spectroscopy and fluorescence decay lifetimes, respectively. Under the excitation of 394 nm, intense red emission in the visible region was observed in Eu3+ doped SGT phosphors, and the critical quenching concentration of Eu3+ in SGT phosphors was derived to be 15 mol%. The chromaticity coordinates and color purity of SGT: 15 mol% Eu3+ were calculated to be (0.61, 0.36) an 93.82 %, respectively. Meanwhile, it was also confirmed that the electric quadrupole–quadrupole interaction is responsible for the luminescence concentration quenching of Eu3+. The internal quantum efficiency of SGT: Eu3+ phosphors with different Eu3+ concentrations were calculated. Furthermore, the crossover process was confirmed to be the main mechanism for luminescence thermal quenching based on the temperature-dependent emission spectra and temperature-dependent fluorescence lifetimes. In addition, the Judd-Ofelt parameters, radiative transition rates and branch ratios from the 5D0 emitting states to various lower energy states were evaluated with the aid of the Judd-Ofelt theory, respectively. All results indicate that SGT: Eu3+ samples are a promising red-emitting phosphor.

During the process of developing commercial chips, the phosphors with single broadband emission are indispensable. In this report, a new ternary phosphate phosphor Na 3 Ba 2 Ca(PO 4) 3 :Eu2+ has been successfully synthesized by the high-temperature solid-state reaction (HSSR) method, which shows broad emitting band in the range of 350–600 nm centered at 436 nm (FWHM ∼ 72.3 nm). The crystal structure of the Na 3 Ba 2 Ca(PO 4) 3 and Eu2+ doped Na 3 Ba 2 Ca(PO 4) 3 were determined by the Rietveld method, indicating the trigonal system with P 31 c space group. The selective two-site occupancy tendency of Eu2+ ions at Ba1O 9 and Ca2O 8 sites in the matrix was comprehensively revealed according to the split peaks (433 nm and 469 nm) at 298 K and 11 K, computational validation and fluorescence lifetime analysis of photoluminescence spectrum. Impressively, the optimal Na 3 Ba 2 Ca(PO 4) 3 :0.02Eu2+ phosphor exhibits appropriate spectrum resemblance (SR) indexes (58.5% and 72.2%), proper thermostability (78.6%) and excellent chromaticity stability (Δ x = 8.68 × 10−6 and Δ y = 3.64 × 10−5). Besides, the phosphor prepared by HSSR owns the higher internal quantum efficiency of 62.1% in comparison with that synthesized by polymerizable complex (PC) method. The new phosphor can serve as a potential broadband and blue-emitting phosphor for the application of solid-state lighting and plant growth. [Display omitted] • First synthesis of Eu2+ ion doped Na 3 Ba 2 Ca(PO 4) 3 phosphor by high temperature solid phase method. • The internal quantum efficiency of phosphor prepared in this work is 9 times of polymerizable complex (PC) method. • Two site-occupancy of Eu2+ in host was carefully determined. • The Na 3 Ba 2 Ca(PO 4) 3 : 0.02Eu2+ owns good thermostability and chromaticity stability. [ABSTRACT FROM AUTHOR]

In this work, a Eu(TTA)3BIP complex with a novel structure was synthesized and characterized. The Eu(TTA)3BIP complex has a wide excitation band and can be excited by light in the ultraviolet and blue regions. The characteristic red light of Eu(III) is emitted when the complex is excited. The use of the 2‐(Pyrimidin‐2‐yl)‐1H‐benzo[d]imidazole (BIP) ligand improved the UV resistance of the complex. Moreover, the blue light reducing film prepared by the Eu(TTA)3BIP complex can effectively weaken blue light irradiation. In addition, the Eu(TTA)3BIP complex exhibits fluorescence thermal quenching properties. This provides the possibility for temperature sensing. [ABSTRACT FROM AUTHOR]

Broadband near‐infrared (NIR) phosphor‐converted light‐emitting diodes are next‐generation smart NIR light sources. However, the NIR phosphor suffers from serious thermal quenching (TQ), resulting in efficiency reduction and spectral shift. Here, a novel strategy is realized to suppress TQ by minimizing bond angle distortion, completely different from the conventional TQ suppression approach through bond length variation. Li(Sr1−xCax)AlF6:Cr3+ NIR phosphor is taken as an example in which rotation between the two parallel fluorine planes perpendicular to the C3 axis in the [AlF6] octahedron is found to dominate TQ. Increasing x from 0 to 1 reduces the amplitude of the rotation from 16.17° to 5.06°, weakening the electron–phonon coupling and, consequently, raising the TQ temperature significantly from 320 to 570 K. This mechanism is elucidated from both theoretical calculations and spectroscopic studies. The findings open a new horizon for the exploration of thermally stable NIR phosphors. [ABSTRACT FROM AUTHOR]

The thermal quenching effect has not been considered in current research on the first-order kinetics of thermoluminescence. In contrast, thermal quenching as a reality should be contained in theoretical models. In this work, a new fitting function of the thermoluminescence glow curve in terms of peak temperature and intensity is obtained by considering the thermal quenching effect for the first-order kinetics model. The new function reduces to the known first-order fit function by removing thermal quenching parameters. The obtained function was applied to the glow curve of the CaF2:Mn (TLD-400) dosimeter. Since the new model differs from the known first-order fit function, different kinetic parameters extract as the result of the fitting procedure. As the new model involves the thermal quenching effect as a physical entity, the kinetic parameters obtained from the presented model are more accurate and realistic.

Transition metal dichalcogenide (TMD) monolayers and their heterostructures have attracted considerable attention due to their distinct properties. In this work, we performed a systematic investigation of MoS2/WSe2 heterostructures, focusing on their temperature-dependent Raman and photoluminescence (PL) characteristics in the range of 79 to 473 K. Our Raman analysis revealed that both the longitudinal and transverse modes of the heterostructure exhibit linear shifts towards low frequencies with increasing temperatures. The peak position and intensity of PL spectra also showed pronounced temperature dependency. The activation energy of thermal-quenching-induced PL emissions was estimated as 61.5 meV and 82.6 meV for WSe2 and MoS2, respectively. Additionally, we observed that the spectral full width at half maximum (FWHM) of Raman and PL peaks increases as the temperature increases, and these broadenings can be attributed to the phonon interaction and the expansion of the heterostructure's thermal coefficients. This work provides valuable insights into the interlayer coupling of van der Waals heterostructures, which is essential for understanding their potential applications in extreme temperatures. [ABSTRACT FROM AUTHOR]

Efficient broadband green-emitting phosphors are promising for application in high color rendering white light-emitting diodes (LEDs). In this paper, we report on the preparation, crystal structure and photoluminescence properties of a novel green-emitting Ca 2 LaHf 2 GaAl 2 O 12 :Ce3+ (CLaHGA) garnet-type phosphor. All these CLaHGA: x Ce3+ (x = 4, 6, 8, 10, and 12 mol%) phosphors have been synthesized through using the conventional high-temperature solid-state reaction method. It has been found that the optical property of phosphors critically depends on Ce3+ content, and the optimal doping concentration of Ce3+ ions is 6 mol%. The optimal CLaHGA:6%Ce3+ sample has a cubic structure with the space group Ia 3 ‾ d and lattice parameters of a = b = c = 12.62662 Å and V = 2013.08 Å3. The CLaHGA: x Ce3+ phosphors exhibit an intense absorption band in the 300–485 nm range with a peak at 421 nm, due to the spin-allowed and parity-allowed 4f→5d transition of Ce3+ ions. Upon 421 nm excitation, CLaHGA: x Ce3+ phosphors give rise to bright broad green emission bands in the 435–750 wavelength region with peak ranging from 519 to 531 nm, owing to the spin-allowed and parity-allowed 5d→4f transition of Ce3+ ions. For the optimal CLaHGA:6%Ce3+ sample, its CIE color coordinates and internal quantum efficiency are determined to be (0.3135, 0.4851) and 40.7%, respectively. The full width at half maximum of CLaHGA:6%Ce3+ is much larger than the commercial (Ba,Sr) 2 SiO 4 :Eu2+ green phosphor (124 nm versus 71 nm), while its emission intensity is only about 39% of that of (Ba,Sr) 2 SiO 4 :Eu2+. Besides, the thermal stability of CLaHGA:6%Ce3+ has also been studied. A white LED device is fabricated using the synthesized CLaHGA:6%Ce3+ green phosphors, showing a bright warm-white light emission with high color rendering index of Ra = 89.7 and low correlated color temperature of 4058 K. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

In this study, a series of trivalent europium-doped tungstate and molybdate samples were synthesized using an improved sol-gel and high-temperature solid-state reaction method. The samples had different W/Mo ratios and were calcined at various temperatures ranging from 800 to 1000 °C. The effects of these variables on the crystal structure and photoluminescence characteristics of the samples were investigated. It was found that a doping concentration of 50% for europium yielded the best quantum efficiency based on previous research. The crystal structures were found to be dependent on the W/Mo ratio and calcination temperature. Samples with x ≤ 0.5 had a monoclinic lattice structure that did not change with calcination temperature. Samples with x > 0.75 had a tetragonal structure that remained unchanged with calcination temperature. However, samples with x = 0.75 had their crystal structure solely dependent on the calcination temperature. At 800–900 °C, the crystal structure was tetragonal, while at 1000 °C, it was monoclinic. Photoluminescence behavior was found to correlate with crystal structure and grain size. The tetragonal structure had significantly higher internal quantum efficiency than the monoclinic structure, and smaller grain size had higher internal quantum efficiency than larger grain size. External quantum efficiency initially increased with increasing grain size and then decreased. The highest external quantum efficiency was observed at a calcination temperature of 900 °C. These findings provide insight into the factors affecting the crystal structure and photoluminescence behavior in trivalent europium-doped tungstate and molybdate systems. [ABSTRACT FROM AUTHOR]

In this study, the photoluminescence properties of Y 3 Al 3 MgSiO 12 :Cr3＋ (YMASG:Cr3＋) and Y 3 Al 3 MgSiO 12 : 2%Ce 3 + , Cr3＋ (YMASG:2%Ce 3 + , Cr3＋) were investigated, and the energy transfer from Ce 3 + to Cr3＋ were examined. All phosphor samples were prepared by the aqueous sol–gel method. The phase purity and surface morphology of the obtained sample was evaluated using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). To determine the photoluminescence (PL) properties of YMASG:Cr3＋ and YMASG:2%Ce 3 + , Cr3＋, emission and excitation spectra along with reflection spectra were recorded. PL decay measurements were also performed, and PL lifetime values were determined. It was found that Ce 3 + → Cr3＋ energy transfer efficiency increases with increasing Cr3＋ concentration. To investigate the temperature-dependent emission of YMASG:Cr3＋ and YMASG:2%Ce 3 + , Cr3＋, PL emission, and PL decay measurements were conducted in a temperature range from 77 to 500 K. Temperature-dependent PL decay measurements also revealed that the Cr3＋ ions mainly cause thermal quenching of YMASG:2%Cfe 3 + , 1%Cr3＋ emission. To check the suitability of synthesized materials to be applied for greenhouse illumination, two pcLEDs containing YMASG:Cr3＋ and YMASG:Ce 3 + , Cr3＋ phosphors were constructed. PcLED prototypes applicability for efficient horticulture lighting was also investigated within this study. [Display omitted] • Ce 3 + → Cr3＋ energy transfer occurs in YMASG:Ce 3 + , Cr3＋ phosphors. • QE of YMASG:Ce 3 + , Cr3＋ decreased with increasing Cr3＋ concentration. • pcLEDs containing YMASG:Cr3＋/Ce 3 + , Cr3＋ are suitable for horticultural lighting. [ABSTRACT FROM AUTHOR]

Mn4+‐doped fluorides are popular phosphors for warm‐white lighting, converting blue light from light‐emitting diodes (LEDs) into red light. However, they suffer from droop, that is, decreasing performance at increasing power, limiting their applicability for high‐power applications. Previous studies highlight different causes of droop. Here, a unified picture of droop of Mn4+‐doped K2TiF6, accounting for all previously proposed mechanisms, is provided. Combining continuous‐wave and pulsed experiments on samples of different Mn4+ content with kinetic Monte Carlo modeling, the contributions of absorption bleach, thermal quenching, and Auger quenching at different excitation densities, are quantified. This work contributes to understanding the fundamental limitations of these materials and may inspire strategies to make Mn4+‐doped fluorides more efficient in high‐power applications. [ABSTRACT FROM AUTHOR]

Mn4+‐doped fluorides are popular phosphors for warm‐white lighting, converting blue light from light‐emitting diodes (LEDs) into red light. However, they suffer from droop, that is, decreasing performance at increasing power, limiting their applicability for high‐power applications. Previous studies highlight different causes of droop. Here, a unified picture of droop of Mn4+‐doped K2TiF6, accounting for all previously proposed mechanisms, is provided. Combining continuous‐wave and pulsed experiments on samples of different Mn4+ content with kinetic Monte Carlo modeling, the contributions of absorption bleach, thermal quenching, and Auger quenching at different excitation densities, are quantified. This work contributes to understanding the fundamental limitations of these materials and may inspire strategies to make Mn4+‐doped fluorides more efficient in high‐power applications. [ABSTRACT FROM AUTHOR]

Scientists are increasingly interested in new inorganic luminescence materials that could be excited with near-infrared (NIR) radiation. These materials can be used as luminescent thermometers, bio-imaging agents, anti-counterfeiting pigments, etc. In this manuscript, we report the synthesis and investigation of optical properties of two series of K2Gd(PO4)(WO4):20%Tb3+ (KGPW): the first, KGPW:20%Tb3+ doped with 1–20% Eu3+, and the second, KGPW:10%Yb3+,20%Tb3+ doped with 1–20% Eu3+. The phase-pure specimens were prepared using a solid-state synthesis method. Down-shifting and upconversion luminescence studies have been performed using 340 and 980 nm excitation, respectively. For upconversion emission luminescence, Yb3+ ions were used as sensitizers in the KGPW phosphors. In these phosphors, Yb3+ ions absorb the 980 nm radiation and transfer the energy to Tb3+ ions. At his point, Tb3+ ions either emit themselves or transfer part or all of their energy to Eu3+ ions. It was observed that the emission color of the synthesized phosphors could be successfully tuned from the green to red by varying the Tb/Eu concentration ratio regardless of the 340 or 980 nm excitation. Such color change proves that one luminescent material (KGPW) can provide three colors (i.e., green, orange, and red). Herein, the optical properties, such as reflection, down-shifting excitation and emission spectra, upconversion emission spectra, fluorescence lifetime, thermal quenching, color coordinates, and quantum efficiency, were studied using steady-state and kinetic spectroscopy. [ABSTRACT FROM AUTHOR]

In this study, we developed a technology for broadening the 465 nm and 535 nm excitation peaks of Eu3+:Y2(MoO4)3 via crystal lattice orderly arrangement. This was achieved by powder particle aggregation and diffusion at a high temperature to form a ceramic structure. The powdered Eu3+:Y2(MoO4)3 was synthesized using the combination of a sol–gel process and the high-temperature solid-state reaction method, and it then became ceramic via a sintering process. Compared with the Eu3+:Y2(MoO4)3 powder, the full width at half maximum (FWHM) of the excitation peak of the ceramic was broadened by two- to three-fold. In addition, the absorption efficiency of the ceramic was increased from 15% to 70%, while the internal quantum efficiency reduced slightly from 95% to 90%, and the external quantum efficiency was enhanced from 20% to 61%. More interestingly, the Eu3+:Y2(MoO4)3 ceramic material showed little thermal quenching below a temperature of 473 K, making it useful for high-lumen output operating at a high temperature. [ABSTRACT FROM AUTHOR]

All‐optical responsive nanomaterials, which can rapidly switch between two stable states, have been regarded as the next‐generation memories due to their potential to realize binary information storage and implement on‐chip, integrated photonic neuromorphic systems. Rare earth oxides are preeminent candidates owing to their extraordinary luminescent stability and narrow optical transitions. However, due to the lack of simple and effective optical switches, it is difficult to realize all‐optical data storage, encoding, and retrieval by pure rare earth‐doped luminescent nanoparticles. Here, a rapid and high‐contrast of 104 luminescent switching of Y2O3:Eu3+ nanoparticle between the enhancement and quenching states is achieved by employing the strong light confinement and ultrafast thermal response of localized surface plasmon resonance. A self‐encrypted all‐optical memory is presented with optical information writing, encryption, reading, and re‐writing, and a high‐sensitivity synaptic response of emitters to frequency and light intensity flux, which can be harnessed to encrypt information flows and promote convenient and high‐security information encryption. Such a convenient and secure plasmonic thermally assisted self‐encrypting luminescent switch paves the way for constructing high‐performance stimuli‐responsive rare earth oxide crystals on demand and expanding their applications in various data encryption, anti‐counterfeiting, and rewritable colouration devices. [ABSTRACT FROM AUTHOR]

Tl[CB11H12] was prepared with a reaction of Tl2[CO3] with the acid of the monocarba-closo-dodecaborate anion (H3O)[CB11H12] in aqueous solution as prismatic colorless single crystals by isothermal evaporation from the clear brine. It crystallizes in a monoclinic primitive structure with the space group P21/c (a = 685.64(3) pm, b = 1978.21(9) pm, c = 1006.89(5) pm, β = 132.918(3)° for Z = 4), which can be derived from the halite-type arrangement if the closo-carbaborate cages are considered as spheres. Due to the different atoms in the [CB11H12]− anion, Tl[CB11H12] features interesting C–Hδ+ ∙∙∙ δ−H–B interactions near to non-classical hydrogen bridges ("dihydrogen bonds") and exhibits considerably different luminescence properties compared to regular closo-hydroborates, such as Tl2[B10H10], Tl2[B12H12] and Tl3Cl[B12H12]. Tl[CB11H12] shows strong photoluminescence (PL) at 390 nm, while the excitation bands for this broad band are located at 245 and 280 nm. It is caused by an interconfigurational [Xe]4f145d106s2 (3P1) to [Xe]4f145d106s16p1 (1S0) transition, which is also known as lone-pair luminescence. The quantum yield is rather low (<10 %), which is likely caused by the rather large Stokes shift. In addition, temperature-dependent emission spectra were recorded to determine the thermal quenching curve and the respective quenching temperature. [ABSTRACT FROM AUTHOR]

Rare earth-doped nanomaterials can achieve diverse upconversion luminescence by changing doping ions, presenting them as promising candidates for rapid temperature measurement. However, most upconversion luminescent phosphors have a thermal quenching effect, which greatly weakens the luminous intensity of the material and impairs thermometry performances. Here, we studied the synthesis of Bi 4 Ti 3 O 12 nanosheets tridoped with Er3+, Yb3+, and Nd3+ ions using molten salt method. Notably, this luminescent material demonstrates both thermal quenching and thermal enhancement effects. The unusual phenomenon results in a high sensitivity of the optical temperature sensor based on the inter-ion energy level between Er3+ and Nd3+. At 523 K, this sensitivity reaches 5.94×10−2 K−1, surpassing that of sensors relying on the thermal coupling of only Er3+ ions by nearly ninefold. Our findings suggest a promising strategy to augment the temperature sensing sensitivity of luminescent materials, paving the way for potential applications in precise temperature monitoring. [Display omitted] • The nanosheets are very sensitive to temperature. • Combination of positive and negative thermal quenching effects improves sensitivity. • The temperature measurement accuracy is up to ± 0.5 K. [ABSTRACT FROM AUTHOR]

• A novel far-red emitting NaSr 10 Y 5 W 4 O 30 :Mn4+ phosphor was prepared. • The mechanism responsible for temperature quenching was proposed. • A blue-emitting LED combined with NaSr 10 Y 5 W 4 O 30 :Mn4+ phosphor was packaged. • The packaged pc-LED demonstrates stable luminescence properties. A series of Mn4+-doped NaSr 10 Y 5 W 4 O 30 (NSYWO) phosphors have been successfully synthesized and further characterized to estimate their potentials for application as a far-red emitting component of pc-LED. An XRD analysis and crystal structure refinement have been carried out to characterize its quality. The doping concentration and temperature (80–500 K) dependent luminescence properties as well as decay kinetics have been studied and analyzed. It has been found that Mn4+ substitutes for W6+ sites resulting in far-red emission at 688 nm. The temperature quenching is attributed to thermal activation of an electron from Mn4+ 2E g to 4A 2g state via crossover, yielding an activation energy of 0.35 eV. Furthermore, to assess practical application of the novel phosphor, a blue-emitting LED chip combined with NSYWO: 0.8 mol% Mn4+has been packaged. The light from both the blue-emitting LED chip and NSYWO: Mn4+ phosphor was shown to be effectively utilized, revealing a good promise for application of the phosphor in the field of plant growth lighting. [Display omitted] A novel far-red emitting Mn4+-activated NaSr 10 Y 5 W 4 O 30 phosphor for plant growth lighting. [ABSTRACT FROM AUTHOR]

The current theoretical knowledge about thermoluminescence allows its study through numerical simulations, by solving a set of differential equations that describe system properties. These models, based on experimental evidence, have been used to reproduce the phenomenon of fading and thermal quenching suffered by materials used by Radiation Dosimetry Services such as LiF:Mg;Ti, commercially called TLD-100. These studies have been carried out by adding both possible charge transitions between localized and delocalized levels and complex thermoluminescence models that allow charge transitions between localized levels. • Study of the optical effects of TL materials related to Fading and Thermal Quenching. • Numerical simulation of the realistic behavior of a thermoluminescent material. • Relationship between optical effects and trapped charge transitions between localized levels. • Implementation of transitions between levels located in the Thermoluminescence model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cool white light emissive Y 2 Si 2 O 7 :Dy3+ developed via gel-combustion method, having triclinic crystal structure with P-1 space group. • NUV 352 nm excitation produced different emission peaks of Dy3+ ions, analogous to 4F 9/2 →6H 15/2, 13/2 and 11/2 transitions. • Quadrupole-quadrupole interaction responsible for concentration quenching. • Optimum sample maintain luminescence stability 80.4 % upto 423 K temperature with 0.2503 eV of activation energy. We report on development and properties of Dy3+ doped Y 2 Si 2 O 7 (YPS) phosphor, a key development in efficient, sustainable lighting via phosphor converted white light emitting diodes (pc-wLEDs). Using gel-combustion method, we synthesized a series of Y 2-x Si 2 O 7 :xDy3+ (x = 1–8 mol %) phosphors. The prepared samples were characterized for their structure, morphology and elemental composition using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) respectively. Diffraction exploration verified triclinic structure and phase purity of fabricated samples. TEM image displayed particle agglomeration with nearly spherical structures. Optical parameters were assessed through diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra analysis. On 352 nm excitation, distinct luminous peaks from Dy3+ ions, analogous to 4F 9/2 →6H M (M = 15/2, 13/2, and 11/2) transitions, were observed. Particularly, intense emission at 571 nm resulted from the 4F 9/2 →6H 13/2. The optimal amount of Dy3+ was determined to be 5 mol %, with concentration quenching attributed to quadrupole–quadrupole interaction. Y 1.95 Si 2 O 7 :5 mol % Dy3+ phosphor possessed activation energy of 0.2503 eV and demonstrates good thermal stability. Thus, these results indicate that the synthesized Y 2 Si 2 O 7 :Dy3+ phosphors are well suited for white light applications. [ABSTRACT FROM AUTHOR]

A luminescence quenching enhanced infrared (IR) detector has been developed to achieve highly sensitive recognition of human body by adding metallic luminescence quenchers. Spherical Ag NPs were mixed with Ru(phen) 3 2+ complex to obtain temperature-sensitive Ag/Ruphen/PVDF films. The relationships among luminescence output, temperature rise and silver addition were investigated and a satisfactory combination of enhanced luminescence factor and temperature change was found with an addition of 5 mol% of 71 nm Ag NPs. It is found that the metal-enhanced luminescence output is insignificant compared to its thermal ingredient since silver provides additional possible electron transfer channels, promoting non-radiative transitions and weakening luminescence. Besides, the Ag NPs induced additional temperature rise bringing further reduction of luminescence. The photothermal effect of Ag NPs can attain a higher temperature change under a certain IR radiation without an observed degradation of luminescence output. A coupled optical-thermal model was established to explain the schematic of the constructed infrared thermal detector. The non-invasive detections of moving and stationary human by the detector were successfully demonstrated. The work tends to provide an engineered optical-thermal model in luminophores and construct highly sensitive luminescence-based infrared thermal detectors. [Display omitted] • Improvement of luminescence thermal quenching of luminescence materials by photothermal effect of Ag NPs. • Highly sensitive infrared thermal detection using the coupling effect of photothermal and thermal quenching. • Demonstration of moving and stationary human detection using luminescent thermal detector. [ABSTRACT FROM AUTHOR]

In this work, the luminescent properties of blue-emission (Ca/Sr) 2 P 2 O 7 : Eu2+ phosphors prepared by hydrothermal synthesis method are extensively investigated. The Rietveld refinement verified that Eu2+ was successfully doped into the phosphors. The SEM results showed that the samples of Ca 2 P 2 O 7 and Sr 2 P 2 O 7 were composed of tetragonal particles and short nanorods particles, respectively. Under ultraviolet excitation, the blue emission peak of the sample had a small full width half maximum (FWHM), with Ca 2 P 2 O 7 (λ em = 417 nm, FWHM = 24 nm), Sr 2 P 2 O 7 (λ em = 420 nm, FWHM = 28 nm). The quantum efficiencies of Ca 2 P 2 O 7 : Eu2+ and Sr 2 P 2 O 7 : Eu2+ were 70.13 % and 69.26 %, respectively. Under the temperature of 480 K, the luminescence intensity of Ca 2 P 2 O 7 : 0.03Eu2+ and Sr 2 P 2 O 7 : 0.03Eu2+ phosphors decreased to 30.02 % and 82.47 % of the initial intensity. Therefore, (Ca/Sr) 2 P 2 O 7 : Eu2+ phosphors with narrow-band blue emission have potential applications in Light emitting diodes and transparent display. • (Ca/Sr) 2 P 2 O 7 : Eu2+ phosphors were synthesized via the hydrothermal synthesis method. • Sr 2 P 2 O 7 : Eu2+ phosphor composed of short rods, about 700 nm in length and 200 nm in width. • The FWHM of Ca 2 P 2 O 7 : 0.03Eu2+, Sr 2 P 2 O 7 : 0.03Eu2+ were 24 nm, 28 nm, respectively. • The quantum efficiencies of Ca 2 P 2 O 7 : Eu2+ and Sr 2 P 2 O 7 : Eu2+ were 70.13 % and 69.26 %, respectively. • At 480 K, the luminescence intensity of Sr 2 P 2 O 7 : 0.03Eu2+ phosphors decreased to 82.47 % of the initial intensity. [ABSTRACT FROM AUTHOR]

Abstract Here, we report a very sensitive, non-contact, ratio-metric, and robust luminescence-based temperature sensing using a combination of conventional photoluminescence (PL) and negative thermal quenching (NTQ) mechanisms of semiconductor BiFeO3 (BFO) nanowires. Using this approach, we have demonstrated the absolute thermal sensitivity of ~ 10 mK−1 over the 300–438 K temperature range and the relative sensitivity of 0.75% K−1 at 300 K. Further, we have validated thermal sensitivity of BFO nanowires quantitatively using linear regression and analytical hierarchy process (AHP) and found close match with the experimental results. These results indicated that BFO nanowires are excellent candidates for developing high‐performance luminescence-based temperature sensors. Graphical abstract

The silicon‐based light‐emitting devices are the bottleneck of fully integrated silicon photonics. Doping silicon with erbium (often along with oxygen) is an attractive approach to turn silicon into a luminescent material, which has been explored for decades. One of the main challenges is the strong thermal quenching effect that results in weak photoluminescence (PL) efficiency. Herein, it is shown that the co‐doping of fluorine with erbium ions can significantly suppress the thermal quenching effect and Auger recombination, resulting in a three‐order‐of‐magnitude increase in PL compared to Er/O‐doped crystalline silicon. As a result, relatively strong PL is observed from fluorine‐doped silicon at room temperature.

Bi ions-doped materials have attracted increasing attention because of their potential applications in LED light sources and imaging displays. However, the correlation between local glass network structure and visible emission of Bi ions is rarely discussed, which hinders the optimization of Bi ions-doped glass. In this work, we prepared the Bi ions-doped borosilicate glasses (Bi-Glass) with tunable visible emissions by changing the content of B 2 O 3. Their optical properties, structure, and temperature-dependent emission were investigated systematically. All the Bi ions-doped glasses show broadband luminescence from 350 nm to 700 nm, the emission bands show a blue shift from 454 nm to 435 nm when the concentration of B 2 O 3 increases from 0% to 10%. The emission intensity reaches the maximum value of 5% B 2 O 3 concentration, which attributes to the number and distribution of bismuth ions luminescent centers. Furthermore, thermoluminescence is observed in this glass system. In this study, the coordination structure around the active centers of bismuth can be changed by modifying the glass network structure, promoting the research of tunable luminescence of bismuth ions-doped glass. [ABSTRACT FROM AUTHOR]

This research aims at investigating the deterioration of limestone rocks due to the influences of thermal quenching and salt crystallization weathering tests and predicting their long-term durability. Therefore, six types of limestones were quarried from different provinces of Egypt and subjected to 50 cycles of thermal quenching and 25 cycles of salt crystallization weathering processes. The porosity, Schmidt hammer rebound hardness, ultrasound pulse velocity, Brazilian tensile strength, and uniaxial compression strength were determined before and after weathering processes. In addition, the mathematical decay function model was developed to evaluate the degradation rate of samples against weathering processes. Results proved that the cyclic salt crystallization deteriorates the physico-mechanical characteristics of the studied limestone more strongly than the thermal quenching cycles do. The decay constant and half-life indexes obtained here indicate that the degradation rate differs for various limestone specimens under thermal and salt weathering processes. This model also showed that the deterioration rate of the studied rocks was higher during cyclic salt crystallization in comparison with thermal quenching. Therefore, the rock degradation rate and or long-term durability under cyclic thermal and salt processes can be estimated accurately. These results show that the studied limestones can be used as building stones in regions exposed to frequent cyclic thermal and salty weathering conditions for long periods without degradation. However, partial attention should be given to LSG limestone rocks characterized by increased porosity and water absorption characteristics. [ABSTRACT FROM AUTHOR]

Optical thermometry, especially the recently developed single-band ratiometric (SBR) temperature measurement method, has attracted considerable attention. However, SBR thermometry, compared with the traditional dual-band ratiometric method, is quite limited as it is still in infancy stage. In this paper, we propose a novel SBR thermometry depending on the combination of charge transfer state as well as ground state absorption. Upon excitation of these two different mechanisms, the red emission of Pr3+ (3P 0 →3F 2 transition) in the low-cost host of calcium tungstate shows totally reverse response to the variation of temperature. Relying on this interesting feature, a sensitive SBR thermometry is established with success, and its optical property has been also investigated in detail. The maximum relative sensitivity is found to be ∼1.5% K−1 at 380 K. [ABSTRACT FROM AUTHOR]

Excitation and photoluminescence spectra of CaAl2O4:Eu3+ nanoluminophores were studied over wide intervals of temperature from 10 to 300 K and laser excitation level from 40 to 2.3·103 kW/cm2. Photoluminescence spectra of CaAl2O4:Eu3+ had the shape of narrow lines and were located at 550–750 nm in the visible spectral region. The position and shape of the photoluminescence spectra of the investigated nanopowders were extremely stable at high levels of laser excitation up to 2.3·103 kW/cm2 at a constant luminescence efficiency up to 60 kW/cm2. The photoluminescence efficiency dropped reversibly if the excitation level was increased further. The threshold of an irreversible drop in the luminescence efficiency was not reached. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenide (TMD) monolayers and their heterostructures have attracted considerable attention due to their distinct properties. In this work, we performed a systematic investigation of MoS2/WSe2 heterostructures, focusing on their temperature-dependent Raman and photoluminescence (PL) characteristics in the range of 79 to 473 K. Our Raman analysis revealed that both the longitudinal and transverse modes of the heterostructure exhibit linear shifts towards low frequencies with increasing temperatures. The peak position and intensity of PL spectra also showed pronounced temperature dependency. The activation energy of thermal-quenching-induced PL emissions was estimated as 61.5 meV and 82.6 meV for WSe2 and MoS2, respectively. Additionally, we observed that the spectral full width at half maximum (FWHM) of Raman and PL peaks increases as the temperature increases, and these broadenings can be attributed to the phonon interaction and the expansion of the heterostructure’s thermal coefficients. This work provides valuable insights into the interlayer coupling of van der Waals heterostructures, which is essential for understanding their potential applications in extreme temperatures.

In this study, a series of trivalent europium-doped tungstate and molybdate samples were synthesized using an improved sol-gel and high-temperature solid-state reaction method. The samples had different W/Mo ratios and were calcined at various temperatures ranging from 800 to 1000 °C. The effects of these variables on the crystal structure and photoluminescence characteristics of the samples were investigated. It was found that a doping concentration of 50% for europium yielded the best quantum efficiency based on previous research. The crystal structures were found to be dependent on the W/Mo ratio and calcination temperature. Samples with x ≤ 0.5 had a monoclinic lattice structure that did not change with calcination temperature. Samples with x > 0.75 had a tetragonal structure that remained unchanged with calcination temperature. However, samples with x = 0.75 had their crystal structure solely dependent on the calcination temperature. At 800–900 °C, the crystal structure was tetragonal, while at 1000 °C, it was monoclinic. Photoluminescence behavior was found to correlate with crystal structure and grain size. The tetragonal structure had significantly higher internal quantum efficiency than the monoclinic structure, and smaller grain size had higher internal quantum efficiency than larger grain size. External quantum efficiency initially increased with increasing grain size and then decreased. The highest external quantum efficiency was observed at a calcination temperature of 900 °C. These findings provide insight into the factors affecting the crystal structure and photoluminescence behavior in trivalent europium-doped tungstate and molybdate systems.

The minimization of thermal quenching, which leads to luminescence loss at high temperatures, is one of the most important issues for near‐infrared phosphors. In the present work, we investigated the properties of near‐infrared Ca(Sc,Mg)(Al, Si)O6 : Cr3+ phosphors with a pyroxene‐type structure under blue light excitation. The CaScAlSiO6 : Cr3+ end member of Ca(Sc,Mg)(Al,Si)O6 : Cr3+ phosphor led to broadband emission at a full‐width half maximum of 215 nm, whereas the CaMgSi2O6 : Cr3+ end member exhibited high thermal stability at 150 °C, with an intensity of 88.4 % of that at room temperature. The structural analysis and density functional theory calculations revealed the absence of soft conformations and local space confinement contributed to the high structural rigidity and weakened the thermal quenching effect. [ABSTRACT FROM AUTHOR]

(Ce0.002 Y0.998âˆ' x Lu x)AlO3 (x  = 0.000, 0.010, 0.100, 0.200) single crystals were grown and characterized to clarify the effects of Lu substitution in Ce:YAlO3 on its crystal structure, optical properties and thermal stability of Ce3+ luminescence. The lattice constants of (Ce0.002 Y0.798 Lu0.200)AlO3 were comparable to those of Ce:YAlO3, so the crystal structure was not significantly influenced by Lu substitution. Concerning the optical characterization, the absorption and emission spectra were almost the same regardless the amount of Lu substitution. This result is consistent with the assumption that the crystal field is not influenced by Lu substitution. The temperature dependences of the photoluminescence decay time showed that the quenching temperature (T 50%) tends to increase with the increasing Lu concentration. We conclude that the leading quenching mechanism is the thermally activated ionization which is suppressed by the Lu substitution in Ce:YAlO3. [ABSTRACT FROM AUTHOR]

Zn2GeO4 microrods obtained by thermal evaporation of a compacted powder mixture of ZnO and Ge exhibit quite intense UV luminescence at low temperatures. Herein, the luminescence properties of Zn2GeO4 microrods are studied for 2:1 and 1:1 ZnO:Ge ratio in the precursor mixture. In both cases, Zn2GeO4 microrods of high crystal quality produce a 355 nm emission under aforementioned bandgap excitation conditions at low temperatures. However, this emission vanishes at room temperature (RT) in the 1:1 samples while it is kept in the 2:1 ones. Herein this work, the thermal quenching of the UV luminescence is studied by means of steady and time‐resolved photoluminescence techniques from 4 K up to RT for both Zn2GeO4 microrods. The analysis of the results leads us to conclude that although the luminescence mechanisms are the same in both cases, a higher decay rate is observed in the 1:1 in both intensity and lifetime, which explain the observed thermal quenching at RT. [ABSTRACT FROM AUTHOR]

High-temperature solid-state reaction technique was used to prepare NaY(MoO 4) 2 :Tb3+ phosphors with different Tb3+ concentrations. XRD patterns showed that the prepared samples contained only single-phased compound NaY(MoO 4) 2. The concentration-dependent green luminescent intensity of Tb3+ was studied, and it was found that the concentration quenching process is in charge of Ozawa's model. The concentration-effect of luminescence decay of 5D 4 level was explained by the Auzel's self-generated quenching theory. Starting from the Reisfeld's theory, the analysis on the luminescence decays also indicated exchange interaction was responsible for the concentration quenching. Temperature dependences of the green emission intensity and decay were comprehended based on the crossover mechanism. A novel temperature sensing technique rooting in the fluorescence dynamics of 5D 4 level of Tb3+ in NaY(MoO 4) 2 was proposed, and the absolute and relative sensitivities were deduced and assessed. [ABSTRACT FROM AUTHOR]

Quantum rod (QR) on-chip LED is considered to be a cost-effective application method, but the thermal stability of the material is one of the prime concerns. Thermally induced photooxidation of nanomaterials, in a water-oxygen environment, is the main reason for the attenuation of its luminous intensity. In order to provide an optimized solution and improve device performance, we attempted to analyze the QR composition of CdSe/CdS and CdSe/CdS/ZnS QRs after decay using X-ray photoelectron spectroscopy (XPS) technique and studied the Attenuation mechanisms. [ABSTRACT FROM AUTHOR]

In the dual‐emitting Eu3+‐activated Sr2NaMg2V3O12 garnet, vibrationally induced thermometric response and thermochromic luminescence are investigated for the first time. Based on the diverse thermal quenching of VO43− and Eu3+ along with the advantage of variation in the fluorescence intensity ratio, a potential phosphor for sensitive dual‐mode ratiometric and colorimetric temperature sensors is proposed in which maximum absolute and relative sensitivity of 0.0135 K−1 and 1.61% K−1 are obtained at 420 K with a temperature resolution

Thermal quenching as an important and well-known effect in compounds exhibiting thermoluminescence, should be considered in thermoluminescence studies. Among the models describing the thermoluminescence phenomenon, the mixed order kinetic model provides a more realistic description of this behavior. In this work, the Thermal quenching effect is included in the mixed order kinetic model and the new thermoluminescence glow curve deconvolution function is obtained in terms of the maximum intensity and the maximum intensity temperature. The new equation reduces to the known mixed order model by equating the thermal quenching parameter to zero. Also the kinetic parameters of the peak 5 of LiF: Mg, Ti (TLD-100) thermoluminescence dosimeter considering the new equation (with Thermal quenching effect) and the previous equation (without Thermal quenching effect) for different heating rates are determined and the results are compared.

This work concerns Cr3+ and Nd3+ co-activated SrGa12O19 phosphors, which were synthesized by high temperature solid-state method using oxides and carbonates as starting materials. Luminescent samples according to SrGa12O19:Cr3+,Nd3+ comprise Cr3+ for the absorption of UV and visible radiation (250–700 nm) prior to energy transfer to Nd3+. The result of the energy transfer between Cr3+ and Nd3+ is the observation of line emission originating from Nd3+ in the near infrared range. The energy transfer from Cr3+ to Nd3+ is discussed via the variations of the lifetime values of Cr3+, and the thermal quenching behavior is also described. The strong absorption of Cr3+ in the visible range and the efficient energy transfer from Cr3+ to Nd3+ indicate that the herein presented material type can serve as a radiation converter to improve the efficiency of photovoltaic devices based on silicon cells.