Co-doped Phosphors Research Articles

Blue LED-pumped intense short-wave infrared luminescence based on Cr3+-Yb3+-co-doped phosphors

The growing demand for spectroscopy applications in the areas of agriculture, retail and healthcare has led to extensive research on infrared light sources. The ability of phosphors to absorb blue light from commercial LED and convert the excitation energy into long-wavelength infrared luminescence is crucial for the design of cost-effective and high-performance phosphor-converted infrared LEDs. However, the lack of ideal blue-pumped short-wave infrared (SWIR) phosphors with an emission peak longer than 900 nm greatly limits the development of SWIR LEDs using light converter technology. Here we have developed a series of SWIR-emitting materials with high luminescence efficiency and excellent thermal stability by co-doping Cr3+-Yb3+ ion pairs into Lu0.2Sc0.8BO3 host materials. Benefitting from strong light absorption of Cr3+ in the blue waveband and very efficient Cr3+→Yb3+ energy transfer, the as-synthesized Lu0.2Sc0.8BO3:Cr3+,Yb3+ phosphor emits intense SWIR light in the 900–1200 nm from Yb3+ under excitation with blue light at ~460 nm. The optimized phosphor presents an internal quantum yield of 73.6% and the SWIR luminescence intensity at 100 °C can still keep 88.4% of the starting value at 25 °C. SWIR LED prototype device based on Lu0.2Sc0.8BO3:Cr3+,Yb3+ phosphor exhibits exceptional luminescence performance, delivering SWIR radiant power of 18.4 mW with 9.3% of blue-to-SWIR power conversion efficiency and 5.0% of electricity-to-SWIR light energy conversion efficiency at 120 mA driving current. Moreover, under the illumination of high-power SWIR LED, covert information identification and night vision lighting have been realized, demonstrating a very bright prospect for practical applications.

Sensitive mechanoluminescence from Eu2+, Tm3+ co-doped Sr3Al2O5Cl2 phosphors

In this paper, sensitive mechanoluminescence (ML) phosphors Sr3Al2O5Cl2:Eu2+, Tm3+ have been developed. The effect of co-doped Tm3+ ions on the ML properties of the samples were investigated. The results showed that the ML emission, afterglow emission and photoluminescence were similar all consisted of a broad band peated at 610 nm, which can be ascribed to the 4f65 d1→4f7 transition of Eu2+. This result indicated that the ML also originated from the Eu2+ emitting center not the Tm3+ ions. The thermoluminescence and ML results have confirmed that the shallow traps (0.656 eV) created by the Tm3+ ions answered for the origin of sensitive ML. Furthermore, following the increase of co-doped Tm3+ ions, the density of shallow trap increased greatly, which brought out strong sensitive ML intensity accordingly. When the content of Tm3+ reached 0.05, sensitive ML intensity of the sample arrived at the strongest under the compressive load of 10–50 N. In addition, the obtained results also showed that the deep traps can provide the possibility to produce long time stable ML emission under strong compressive load of 10–800 N. Even after 120 min, stable obvious ML signals can be observed. All these results suggested that Sr3Al2O5Cl2:Eu2+, Tm3+ phosphors possessed great potential in precious detection of weak stress and long time stable ML detection.

Up-conversion luminescence performance of Tm3+/Yb3+ co-doped strontium cerate phosphors

Tm3+/Yb3+ co-doped Sr2CeO4 phosphors were fabricated via a high-energy ball milling technique. The structural, morphological, and luminescence characteristics were analyzed by XRD technique, field emission scanning electron microscopy, and up-conversion luminescence spectra, respectively. The structural X-ray diffraction patterns indicate their orthorhombic structure. Under excitation at 975 nm, the up-conversion luminescence spectra of Sr2CeO4:Tm3+/Yb3+ samples with various concentrations of Yb3+ were observed. The phosphor containing 10 mol% Yb3+ ions exhibited optimal up-conversion luminescence. All the samples show emission peaks at 478, 652, and 801 nm, which are assigned to the 1G4 → 3H6, 1G4 → 3F4, and 3H4 → 3H6 transitions of Tm3+. A detailed analysis of the up-conversion mechanisms is proposed based on simplified energy level diagram. The results show that the Sr2CeO4:Tm3+/Yb3+ phosphor has potential application prospects in wide-range and light emitting devices.

Tm3+/Yb3+ codoped CaGdAlO4 phosphors for wide-range optical temperature sensing

In this paper, single-phase CaGd1-x-yTmxYbyAlO4 (CGA:Tmx,Yby, 0.0005 ≤ x ≤0.005, 0.06 ≤ y ≤0.14) phosphors were synthesized by a combustion method in combination with a following heattreatment. It is found that their average grain sizes are in the range of ∼0.60–1.74 μm. For these phosphors under 980 nm excitation at room temperature, four sharp emission bands at 474, 651, 693 and 801 nm can be attributed to the 1G4→3H6, 1G4→3F4, 3F2,3 → 3H6 and 3H4→3H6 transitions of Tm3+ involving in the three-photon and two-photon processes. When x and y are equal to 0.001 and 0.10, respectively, the strongest UC emission intensity can be acquired. By employing the optimal phosphors, the wide-range temperature sensing from 173 to 823 K was realized based on LIR693/801 and FWHM801 parameters. The SA−LIR and SR−LIR in the temperature range from 300 to 823 K are in the range of 0.19–6.55 × 10−4 K−1 and 2.93–0.38 × 10−2 K−1, respectively. The SA−FWHM and SR−FWHM in the temperature range from 173 to 823 K are in the range of 4458-2044 × 10−4 K−1 and 0.20–0.05 × 10−2 K−1, respectively. Furthermore, our result demonstrates that CGA:Tm0.001,Yb0.1 phosphors has potential applications in wide-range optical temperature sensing working under extreme conditions.

A dual-mode self-referenced optical thermometry with high sensitivity based on Er3+-Yb3+ co-doped Sr2YTaO6 thermochromic phosphor

Up conversion luminescent materials Sr2YTaO6: Er3+, Yb3+ phosphors were prepared by high temperature calcination. In view of the formation, temperature characteristics, and photoluminescence features of the sample, X-ray diffraction and photoluminescence were used. Under the excitation at 980 nm, the series of samples is significantly stimulated by Er3+ up-conversion luminescence and Yb3+ sensitization at 524, 550 and 659 nm. According to the diversity of temperature sensing performance from these three highest peaks, a dual-mode temperature sensor on account of fluorescence intensity ratio (thermally coupled level between 2H11/2 and 4S3/2, and nonthermally coupled energy levels between 2H11/2 and 4F9/2) is achieved by using a single luminescent center. Moreover, the phosphor has strong thermal stability, which is helpful to improve the accuracy of temperature measurement. Under the temperature measurement of a dual-mode temperature sensor, it is calculated that the optimal absolute sensitivity Sa of thermally coupled energy level is 0.78 × 10−3 K−1 (473 K) and relative sensitivity Sr is 1.32 %K−1 (293 K), and the maximum optimal absolute sensitivity Sa of non-thermally coupled energy level is 1.02 × 10−4 K−1 (473 K) and relative sensitivity Sr is 0.58 %K−1 (293 K). All results imply that Sr2YTaO6: Er3+, Yb3+ phosphors are promising materials for self-referenced optical temperature measurement.

Electronic and optical responses, Compton spectroscopy and manifestation of trapping centres of LiF:Mg,Ti

Electronic structure to judge trapping centres and activation energies in Mg-doped (2–8%) and Mg,Ti co-doped (2–3% each) LiF phosphors are presented using full-potential linearized APW method. Compton measurement for LiF is performed for appropriate choice of exchange-correlation potentials used in electronic properties. It is seen that 2–6% of Mg activator leads to formation of electronic traps with activation energy between 0.79 and 0.49 eV. At high concentration (>6%) of Mg, the formation of trap centres vanishes. Co-doping of 2% Mg,Ti permits the formation of trap centres, which is in contrast to higher concentrations. Mg-3s states play key role in the building of electronic trap centres. Higher concentration of Ti and Mg activators in LiF leads to the widening of 3d and 3s states, respectively. Analysis of optical response (frequency-dependent dielectric constants, trapping centres, and absorption coefficients) of 2% Mg-doped and 2% Mg,Ti co-doped LiF suggest their dosimetric applications and in ultra-violet detection.

Photoluminescence properties and energy transfer of ZnNb2O6: Eu3+, Sm3+ orange-red phosphors for WLEDs

Eu3+, Sm3+ co-doped ZnNb2O6 orange-red phosphors were synthesized through the solid-state reaction method for the first time. The microstructure, photoluminescence properties, decay time, energy transfer mechanism, thermal stability and CIE chromaticity coordinates of Zn1-x-yNb2O6: xSm3+, yEu3+ phosphors were studied systematically. The XRD patterns and refinement results demonstrate that the rare earth ions have been effectively doped into ZnNb2O6 host lattices. Under the excited of 406 nm, the main emission peak intensity of Sm3+ decreased and Eu3+ increased with increasing of Eu3+ ion concentration in the Zn0.99-yNb2O6: 0.01Sm3+, yEu3+ phosphors, which due to the energy transfer from Sm3+ to Eu3+. Through the decay time measurements, energy transfer mechanism was proved to the electric dipole-electric dipole effect in the resonance transfer mode, and the transfer efficiency of ZnNb2O6: 0.25Eu3+, 0.01Sm3+ phosphor is calculated as 85.39%. Through the analysis of thermal stability properties of the co-doped sample, the thermal activation energy of thermal quenching is calculated to be 0.235 eV. The CIE chromaticity coordinates for co-doped sample are located at the orange-red region, the correlated color temperature and color purity are calculated to be 1927 K and 95.87%, respectively. In addition, a WLED device can be obtained by combing the co-doped sample with commercial blue (BaMgAl10O17: Eu2+) and green ((Sr, Ba)2SiO4: Eu2+) phosphors on a 395 nm N-UV LED chip. These results indicate that ZnNb2O6: Eu3+, Sm3+ phosphor is a promising candidate for WLEDs.

Luminescent properties and mechanism study of Yb3+/Er3+ Co-doped GdBa3B9O18 phosphors

Er3+ and Yb3+ co-doped phosphors Gd0.97-xEr0.03YbxBa3B9O18 (x = 0, 1%, 5%, 10%) were synthesized by high temperature solid-state method. X-ray diffraction (XRD) measurements showed that the synthesized samples have a hexagonal structure. The excitation spectra and emission spectra were measured under different excitation conditions. With the increasing of Yb3+ concentration, the visible emission intensity of Er3+ decreases but the near-infrared emission of Yb3+ increases under the excitation of cyan light. Through down-conversion, the quantum efficiency of Yb3+ with concentration of 10% was calculated up to 130%. When the phosphor is excited with 980 nm infrared laser, the up-conversion visible emission intensity increases with the increasing of Yb3+ concentration. The result indicated that Yb3+ can sensitize the up-conversion luminescence of Er3+. The present work shows that the energy transfer between Yb3+ and Er3+ ions is reversible at different excitation wavelengths.

Adjustable luminescence properties of Eu3+ and Bi3+ codoped Ca3Zn3Te2O12 phosphor

Ca3Zn3Te2O12:Bi3+, Ca3Zn3Te2O12:Eu3+, Ca3Zn3Te2O12:Eu3+/Bi3+ are prepared successfully in air. The crystal phase, microscopic image, and optical properties of samples are investigated by the X-ray difractometer, scanning electron microscopy, and edinburgh steady-state FLS 980 spectrograph. The green emission of Ca3Zn3Te2O12:Bi3+ phosphor with excitation at 314 nm is observed and its broad emission spectrum in the range of 360 - 790 nm is attributed to the 3P1 → 1S0 transition of Bi3+ ion. Under excitation at 395 nm, the red emission of Ca3Zn3Te2O12:Eu3+ is found, the chromaticity coordinates are (0.6392, 0.3605), and its PL spectrum is in the rang of 575 - 750 nm because of the 5D0 → 7F0,7F1, 7F2, 7F3, and 7F4 transations of Eu3+ ion. The doping Bi3+ ion can affect the luminescence properties of Ca3Zn3Te2O12:Eu3+ phosphor. The adjustable color light from green to yellow of Ca3Zn3Te2O12:Eu3+, Bi3+ phosphor with excitation at 314 nm is revealed when Eu3+ concentration is changed from 0 to 12 mol%. When the excitation wavelength is 395 nm, Ca3Zn3Te2O12:Eu3+, Bi3+ phosphor only emits red light with emission spectrum in the rang of 575 - 750 nm. The energy level diagrams of Eu3+ and Bi3+ in Ca3Zn3Te2O12:Eu3+, Bi3+ are drawn, which is used to analyze the luminous mechanism of samples.

Tunable multicolor luminescence and energy transfer mechanism in Eu3+/Dy3+ co-doped Ca2Sb2O7 phosphor under UV excitation

A series of Ca(2-x-y)Sb2O7:xDy3+,yEu3+ phosphors with tunable multicolor luminescence were synthesized via solid-state reaction method. The XRD, EDX and HR-TEM analysis confirmed the phase purity and the crystallinity of the samples. Under ultraviolet (UV) excitation, Ca(2-x-y)Sb2O7:xDy3+,yEu3+ phosphors exhibit characteristic emission bands of both Dy3+ and Eu3+ ions, along with an intense blue emission band of the host. The emission peaks at 575 and 660 nm correspond to 4F9/2 →6H13/2 and 4F9/2 →6H11/2 transitions of Dy3+ ions, and the peaks at 528 and 612 nm originate from 5D1 →7F1 and 5D0 →7F2 transitions of Eu3+ ions, respectively. There exists efficient energy (ET) transfer from host to Eu3+/Dy3+ ions, as well as from Dy3+ to Eu3+ ions. The decay lifetime of host and Eu3+/Dy3+ emissions were calculated to be in the microsecond range. By properly modulating the concentration of Eu3+/Dy3+ ions, the CIE chromaticity coordinates of the samples vary from (0.144, 0.097) to (0.446, 0.312). Hence, multicolor emission which can be tuned from blue to bluish-white and eventually to reddish-white can be obtained in the warm CCT region. The results indicate that Ca2Sb2O7:Dy3+,Eu3+ phosphor could be a promising candidate for UV excited WLEDs and multicolor displays.

Eu3+ and Mn4+ co-doped BaLaMgNbO6 double perovskite phosphors for WLED application

Red light component for white light emitting diodes (WLEDs) keeps attracting the researchers’ attention to obtain high color rendering index (CRI). Here, Eu3+ and Mn4+ co-doped BaLaMgNbO6 double perovskite red phosphors were acquired by solid-state reaction method. Both the red emission of Eu3+ and deep-red emission of Mn4+ could be realized under the excitation of near ultraviolet light. The concentrations of Eu3+ and Mn4+ in BaLaMgNbO6 were optimized to be 30.0 mol% and 0.1 mol%, respectively. Temperature dependent emission of Eu3+ and Mn4+ were carried out to reveal the thermal stability of this red phosphor. Optimized BaLa0.7Eu0.3MgNb0·999Mn0·001O6 was mixed with commercial blue and green phosphors to obtain WLEDs. The CRI of the fabricated device reaches 90.2, confirming this red phosphor an excellent candidate as red light compensation for WLEDs.

Tunable luminescent chromaticity of CaZnOS: Bi3+, Eu3+ with white emitting based on energy transfer

A series of Bi3+ or Eu3+ ion single doped and Bi3+ and Eu3+ co-doped CaZnOS phosphors were synthesized via high temperature solid state method. Under ultraviolet (UV) excitation, CaZnOS: Bi3+ has an intense emission band ranged from 400 to 600 nm owing to the 3P1,0 → 1S0 transition of Bi3+. And CaZnOS: Eu3+ shows superior red emissions due to the characteristic 5D0 → 7FJ (J = 1, 2, 3, 4) transitions of Eu3+. Tunable emission chromaticity from cyan, white, yellow to red is obtained by regulating the proportion of Eu3+ in CaZnOS Bi3+, Eu3+. The energy transfer mechanism from Bi3+ to Eu3+ was confirmed to be a quadrupole-quadrupole interaction based on the overlap of emission band of Bi3+ and excitation band of Eu3+ combined with the luminescent lifetime measurement. In addition, CaZnOS: 2.5 mol% Bi3+, 3 mol% Eu3+ phosphor with optimized concentrations has standard white light chromaticity coordinates (0.315, 0.323) and activation energy about 0.372 eV, which reflects its potential application in ultraviolet-chip excited white light emitting diodes (W-LEDs).

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.

A Temporal and Space Anti-counterfeiting Based on the Four-Modal Luminescent Ba2Zr2Si3O12 Phosphors.

Fluorescent anti-counterfeiting materials have been widely studied due to their high resolution and convenient identification by direct visualization of the color output. To date, the anti-counterfeiting technology of single ultraviolet excitation mode still has security problems because the single mode could be imitated easily. Here, we have successfully developed four modes of anti-counterfeiting from Eu2+ and Er3+ co-doped Ba2Zr2Si3O12 phosphors with photo, long persistent, photo-stimulated, and up-conversion luminescence behavior. The as-fabricated phosphors can emit an intense blue-green luminescence originating from the characteristic transition of Eu2+ ions and exhibit a blue-green long persistent luminescence phenomenon. Moreover, the enhancement of photo-stimulated luminescence that contributed to the effectively increased trap concentration is observed, along with the produced up-conversion phenomenon thanks to the introduction of Er3+ ions. Notably, the fluorescence rapidly changes from blue-green to stable green luminescence with the delay of excitation time under the excitation of a 980 nm laser diode. Herein, this work realizes the fast down- to up-conversion luminescence output over time, which provides the basis for its possible application in advanced multi-mode anti-counterfeiting.

An energy transfer strategy for highly luminescent green-emitting Ce3+/Tb3+ codoped Ca2LaHf2Al3O12 garnet phosphors in white light-emitting diodes

Bright, energy-efficient, and stable white lighting sources, such as light-emitting diodes, are desirable to mitigate climate change. A near-ultraviolet-excitable, green-emitting Ca2LaHf2Al3O12:Ce3+,Tb3+ garnet phosphor with high photoluminescence efficiency, prepared by solid-state synthesis, is described. X-ray diffraction Rietveld refinement reveals its garnet structure with space group Ia3¯d and crystallographic parameters a = b = c = 12.528 Å, α = β = γ = 90°, and V = 1966.470 Å3. On 408 nm excitation, it produces bright green light peaking at 543 nm owing to the 5D4→7F5 transition of Tb3+ ions and demonstrates an ultrahigh internal quantum efficiency (80%) and high external quantum efficiency (59.2%). The luminescence intensity of Ca2LaHf2Al3O12:0.05Ce3+,0.6Tb3+ is double that of a Ca2LaHf2Al3O12:0.05Ce3+ green phosphor owing to Ce3+→Tb3+ energy transfer. This Ca2LaHf2Al3O12:0.05Ce3+,0.6Tb3+ green phosphor was used to fabricate a near-UV-pumped white LED device; the resulting luminous efficacy and color rendering index at 3397 K were 17.56 lm/W and 93.1, respectively.

Improved photoluminescence and multi-mode optical thermometry of Er3+/Yb3+ co-doped (Ba,Sr)3Lu4O9 phosphors

Contactless optical thermometers have attracted extensive attentions for applications in scientific research and technological fields due to their apparent advantages. Herein, a novel sequence of Ba 3-x Sr x Lu 4 O 9 (B 3-x S x LO):Er 3+ /Yb 3+ phosphors were successfully prepared to investigate the temperature sensing property. By establishing energy transfer from Yb 3+ to Er 3+ and regulating the local lattice environment, up-conversion luminescence of Er 3+ is dramatically improved when excited by 980 nm laser. This can effectively promote signal-noise ratio and reduce the errors in temperature detection. Furthermore, a multi-mode optical thermometry, which includes the fluorescence intensity ratio (FIR) from two thermally coupled levels of 2 H 11/2 / 4 S 3/2 , FIR based on non-thermally coupled system of 2 H 11/2 / 4 F 9/2 and fluorescence lifetime of 4 S 3/2 state of Er 3+ , was explored systematically. The fabricated samples exhibit the superior temperature measurement performances containing wide temperature-sensing range, superior signal discriminability, high sensitivity and favorable repeatability, indicative of the enormous utilization prospects of B 3-x S x LO:Er 3+ /Yb 3+ for thermometry.

Up-conversion luminescence and optical temperature sensing of Er3+, Yb3+ co-doped Gd2O3 phosphors with different F-/Ln3+

In this work, the Er3+, Yb3+co-doped Gd2O3 phosphors have been prepared through a facile hydrothermal method. The optimum doping concentration of the Er3+, Yb3+ co-doped Gd2O3 phosphors are studied in detail. By studying the samples calcined at different temperatures, the process of grain forming self-assembled structure was revealed. The up-conversion luminescence intensity of the phosphors can be regulated by the ratio of NH4F and lanthanoid nitrate (F-/Ln3+) in the synthesis process. The enhancement of red and green emission intensities can reach 8.0 times, 6.7 times respectively than the sample with F-/Ln3+ = 0.5. In addition, the florescence intensity ratio based on thermally coupled energy levels by the Stark sublevels is also investigated. The maximal absolute sensitivity of optical temperature sensing reaches 1.27% K−1 at 574 K, which is 1.51 times higher than that based on traditional thermally coupled energy levels by Stark levels. Therefore, the results show that this is a useful method to improve the absolute sensitivity of optical temperature sensing and the Er3+, Yb3+ co-doped Gd2O3 phosphors have application potential in high sensitivity optical temperature sensing.

Novel broadband near-infrared emitting phosphor LiGe2(PO4)3:Cr3+ with tuning and enhancement of NIR emission by codoping Sb5+

A highly efficient novel broadband NIR emission peaking at 814 nm with a large full width at half maximum (FWHM) of 170 nm was realized in novel LiGe2(PO4)3:Cr3+ (LGP:Cr3+) with internal quantum efficiency about 90% (IQE). An innovative strategy of Sb5+ codoped phosphor (LGP:Cr3+,Sb5+) led to the increases in the luminescence intensity and thermal stability. Moreover, tunable NIR emission from 814 to 743 nm was achieved which can be ascribed to the attenuation of electron-phonon coupling with increasing Sb5+-concentration. The output powers of phosphor-converted lighting emitting diodes (pc-LEDs) by combining 460 nm chips with LGP:0.01Cr3+ and LGP:0.05Cr3+,0.05Sb5+ phosphors reached 34.68 mW @ 300 mA and 40.36 mW @ 250 mA, respectively. Our results prove that the codoped strategy can provides a new idea for research on tunable NIR phosphors.

Cation and polyhedron substitution strategies: Effects on local crystal structure and on Bi3+ and Eu3+ co-doped inverse garnet phosphors’ luminescence property

Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg3Gd2Ge3O12: Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO4] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs.

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.