Phosphor Samples Research Articles

Effect of the synthesis route on luminescence dynamics and thermographic properties of Sm3+ doped Ba2Mg(PO4)2 phosphor

The present study investigates the impact of synthesis routes on the structure, optical, and thermographic properties of Ba2Mg(PO4)2:xSm3+ (x = 2 mol.%) phosphor. The two techniques used for the synthesis were combustion synthesis (CS) and solid-state reaction synthesis (SSR). X-ray diffraction analysis confirmed a pure monoclinic phase with space group P21/n in both SSR and CS synthesized samples. The average crystallite size was 41 ± 0.19 nm for SSR and 21 ± 0.02 nm for CS phosphors. Using Fourier transform infrared (FTIR) analysis, the vibrational behavior of both synthesized phosphor samples was analyzed. Both samples displayed a bright orange-red photoluminescence (PL) emission, attributed to the 4G5/2→6H7/2 transition when excited with 403 nm light at room temperature. However, the intensity of PL emission was higher in the CS-prepared sample. The UV-Vis absorption measurements indicated several bands in both samples. The CIE coordinates were calculated for both samples and they corresponded to the shade of orange-red emission of the Sm3+ ions. The study also included an investigation into the temperature-sensing characteristics of the synthesized phosphors, which was performed in the 323–673 K temperature range. The fluorescence intensity ratio (FIR) technique was used to study the non-contact temperature sensing for both samples, and the CS-prepared phosphors exhibited the maximum value of absolute sensitivity (0.00629 K−1) and relative sensitivity (0.26 % K−1) at temperature 673 K. Overall, the results indicate that the CS method provides better results in terms of luminescence and temperature sensing characteristics compared to the SSR method.

Tunable luminescence properties of the Ca3-xLuxSc2-xMgxSi3O12:Ce3+ phosphor based LD lighting

In white-light laser diodes (LD) illumination, the full width at half maximum (FWHM) of the emission spectrum of blue LD is too narrow, leading to the cyan light deficiency, while the emitting color of the material limits the red component of the device. Therefore, in this paper, Ca3-xLuxSc2-xMgxSi3O12:Ce3+ (CLSMS:Ce3+, x = 0, 0.5, 1, 1.5, 2) phosphor samples were successfully prepared based on Ca3Sc2Si3O12 (CSS) cyan-green fluorescent materials with different concentrations of Lu–Mg ions introduced in the matrix instead of Ca–Sc ions. And their luminescence properties were systematically investigated. The peak of the sample was shifted from 508 nm to 590 nm as the concentration of Lu–Mg increased. The thermal stability of the series phosphors gradually deteriorated with increasing Lu–Mg concentration. At 423 K, the emission intensity of the samples was 98.11 %, 94.13 %, 92.18 %, 81.96 % and 77.60 % of that at 298 K, respectively. And the thermal quenching activation energy also gradually decreases. The CLSMS:Ce3+ fluorescent materials were prepared into LD devices and tested. It was found that the series of samples showed a gradual decrease in cyan-green light and a gradual increase in red light with increasing Lu–Mg concentration. The CSS compounded with CaLu2Mg2Si3O12 (CLMS) obtained a white LD device with color coordinates of (0.3440, 0.3455), and the cyan and red components of the samples were compensated. In summary, this study demonstrates that CLSMS:Ce3+ is a very promising fluorescent material to extend the color gamut coverage of fluorescent materials. And it has a potential reference value for the field of white-light LD lighting.

Influence of Annealing Temperature on the Structural and Luminescence Features and Thermoluminescence Trap Parameters of Ca2Al2SiO7: Ce3+ Phosphors

Cerium-doped Ca2Al2SiO7 phosphors were synthesized via the combustion technique and annealed at 1073 K, 1173 K, and 1373 K. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), photoluminescence (PL), and thermoluminescence (TL) studies were performed to explore the variation of structural, morphological, luminescence, and TL properties with annealing temperature. The XRD plot showed an increase in crystallinity with an increase in annealing temperature. Similarly, the enhancement of PL intensity with an increase in annealing temperature supports the increased crystallinity of the phosphor samples. Detailed analysis of traps and trap parameters was carried out using the principle of TL. Samples were irradiated with different γ-ray doses, and, on heating, luminescence was observed. Thus, TL glow curves were drawn and deconvoluted using computerized glow curve deconvolution (CGCD) and Chen’s peak shape method to study the traps and trap parameters. With increasing annealing temperature, an increase in TL intensity was observed. Regardless of annealing temperature, every sample displayed a linear dose–response for doses ranging from 3 Gy to 500 Gy. TL investigations suggested that the produced phosphors are suitable candidates for gamma dosimetry applications.

Bluish-green emission of novel BaAl2Ge2O8:Eu2+ phosphors under near-ultraviolet excitation

A new class of phosphor samples, denoted as Ba1–xAl2Ge2O8:xEu2+ (BAGO:xEu2+) was synthesized using Pechini-type sol–gel technique and subsequently underwent thermal reduction in CO atmosphere. The morphology and structural characteristics of both the BAGO host lattice and the Eu2+ ions activated BAGO phosphors were investigated through field-emission scanning electron microscopy and X-ray diffractometry analyses, respectively. The BAGO host lattice has micro-sized particles and the Rietveld refinement reveals the presence of a monoclinic crystal phase, characterized by the space group I12/c1 (No. 15). Introducing Eu2+ ions into Ba2+ sites under CO conditions reduces the particle size, switching from micrometer to nanoscale. Within the near-ultraviolet spectrum (353 nm), the BAGO:xEu2+ phosphors exhibit a broadband blueish-green photoluminescence (PL) emission characterized by a peak band at 492 nm. This phenomenon is attributed to the 4f6 5d1 → 4f7 electronic transition. The BAGO:0.02Eu2+ phosphor sample exhibits the strongest bluish-green PL emission, and a comprehensive description of the concentration quenching mechanism between Eu2+ ions is revealed. Additionally, the thermal stability of the optimized BAGO:0.02Eu2+ phosphor was investigated, and its activation energy was estimated. Therefore, the synthesized bluish-green BAGO:0.02Eu2+ phosphor holds the promise of being a novel and promising candidate for utilization in white-light-emitting diode applications.

Effect of Ce codoping on the thermoluminescence dosimetry and photoluminescence behavior of SrBPO5:Dy/Sm/Eu

Effect of Ce on the thermoluminescence and photoluminescence of Dy, Sm and Eu in SrBPO5 was investigated. Samples of Sm, Dy, Eu doped and Ce-Dy/Sm/Eu codoped SrBPO5 were prepared through the high temperature solid-state synthesis route. Prepared phosphor samples were checked for their phase purity with powder X-ray diffraction analysis. Thermoluminescence glow curves were recorded for the phosphors and explored for the dosimetric applications. TL glow curves of 20 Gy gamma irradiated SBP:Dy0.01−1/Sm0.01−1/Eu0.01−1 and SBP:Ce1-Dy0.01−1/Sm0.01-Eu0.01−1 were obtained with 2 K/s heating rate. Gamma dose response of the phosphor samples were studied from 5 mGy to 100 Gy. The SBP:Ce1-Dy0.5 and SBP:Ce1-Sm1 demonstrated excellent dose linearity to gamma dose. The thermoluminescence behavior indicated that, Ce codoping has profound effect on the amount and type of traps and the glow peak intensity of Ce codoped SBP:Dy/Sm enhanced significantly. The photoluminescence study suggested efficient exchange type energy transfer interaction between excited states of Ce3+ and Dy3+/Sm3+ in the SrBPO5 host. The results confirmed the suitability of SBP:Ce-Dy/Sm phosphors for the thermoluminescence applications. The range of dose linearity of SBP:Ce-Dy, and SBP:Ce-Sm phosphor were found to be better than the commercial CaSO4:Dy and could be promising materials for personal as well as accidental dosimetry.

Synthesis, Structural and Fluorescence Investigations of Novel Li2Ba5W3O15:Sm3+ Phosphors for Photonic Device Applications.

In the current study, Sm3+ ions doped Lithium Barium Tungstate (Li2Ba5W3O15) (LBW) phosphors with the ability to emit orange-red light were made using the traditional high-temperature solid-state reaction technique. The structure and phase of the as-synthesized phosphor samples were examined via X-ray diffraction (XRD) patterns. The diffraction peaks of the undoped LBW and Sm3+ ions doped LBW phosphors closely resemble those of the Joint Committee on Powder Diffraction Standards (JCPDS) pattern with card number 01-072-1717. Scanning electron microscopy (SEM) was employed for the analysis of the morphological characteristics of the synthesized phosphor material. Fourier Transform Infrared (FT-IR) spectroscopy was used to study several vibrational and molecular bands present in the host matrix. Using diffuse reflectance spectra (DRS), the optical band gap values (Eg) were evaluated by applying Tauc's method. The photoluminescence (PL) spectra characteristics at λex = 336nm indicate the emission of dopant ions (Sm3+) in the deep orange-red region corresponding to 4G5/2 → 6H5/2 transition (at 581nm) with concentration quenching after 2mol % of Sm3+ ions. Using the PL spectra, the CIE chromaticity coordinates of LBWS2.0 phosphor were estimated and found in the deep visible orange-redarea, indicating the potential use of the prepared phosphor material for phosphor-converted white light emitting diodes (w-LEDs) applications. Double exponential behaviour can be seen in the PL decay spectralprofiles obtained under λem = 581nm and λex = 336nm. The experimental lifetimes (τexp) decrease as the concentration of Sm3+ ions rise. The temperature-dependent PL (TDPL) and activation energy results show that the as-synthesized phosphor has considerably superior thermal stability. The results of the current research contemplate us the applicability of Sm3+ ions doped LBW phosphor for photonic devices such as w-LEDs.

Using (Ba,Ca)ScO2F:Bi3+,K+ phosphor with great performance and strong heating stability for LED backlight screens

diodes emit illumination (LED) display study is focused on straitband green phosphor samples yielding significant effectiveness as well as heating consistency. The cation substitution design technique was used to create Ba1-xCaxScO2F:0.001Bi3+,0.001K+ with x of 0-0.12) perovskite phosphors that emit strait green illumination when activated by a 415 nm chip. The impact of Ca2+ replacement for Ba2+ in the crystal structures of Ba1- xCaxScO2F:0.001- Bi3+,0.001K+ and photoluminescence characteristics were examined. In the space group Pm3m, all of the phosphors have a cubic perovskite-type structure. The development of cell characteristics and the lengthiness of the Ba/ Ca/K/Bi-O bonds were studied. Beneath 415 nm chip stimulation, the phosphors with an interior quantum effectiveness of 77.4 percent produce strong green radiation reaching the peak at 510 nm. The increase of luminous effectiveness and heating steadiness in response to local structural change was thoroughly addressed. The cation substitution design technique discussed here might be a significant way to realizing spectrum modulation by regulating the micro-surrounding within the latticework to achieve outstanding LED backlighting screens.

Effect of Mg2+ and Zn2+ addition on photoluminescent and photoacoustic spectroscopy of La2O3:Er3+/Yb3+ phosphors

Photoluminescence (PL) and photoacoustic spectroscopy (PAS) are important techniques for materials characterization. The La2O3: Er3+/Yb3+ phosphors samples were synthesized by combustion method and annealed at 800–1200 °C for 2 h for improved photoluminescence properties. XRD data confirmed that all samples have pure hexagonal phase and FE-SEM shows irregular granular-like morphological structures and particle size that improved with annealed temperature. Then the photoacoustic (PA) amplitude and upconversion (UC) emission intensity were successively measured by a homemade PA cell under 980 nm laser excitation. A comparative relationship was made between PA and UC varying excitation power. Then, the authors showed the effect of codoped Mg2+ and Zn2+ ions on the radiative and non-radiative properties. It is observed that UC emission intensity for Zn2+ codoped La2O3: Er3+/Yb3+ phosphor has maximum, and also observed prominent absorption peaks at 521, 658, and 955 nm. These results indicate its high potential for application in photo-thermal therapy and upconversion imaging.

Pure-green upconversion emission and high-sensitivity optical thermometry of Er3+-doped stoichiometric NaYb(MoO4)2

The optical temperature sensor based on fluorescence intensity ratio (FIR) offers significant advantages for rapid and non-contact temperature measurements. However, the application of optical temperature sensors is limited by the challenge of identifying advanced materials with high response sensitivity. In this study, phosphor and single-crystal states stoichiometric NaYb(MoO4)2 with Er3+ doping were prepared by solid-state reaction method and Czochralski method, respectively, for promising optical thermometry applications. The structure of the phosphor and single-crystal state samples were investigated. High-purity upconversion (UC) emissions were achieved from stoichiometric NaYb(MoO4)2:Er3+ samples with a maximum green-to-red ratio up to 70.3, which opens up numerous possibilities for their application as pure-green color converters. Besides, the UC emission spectra were monitored with respect to temperature, and the fluorescence intensity ratios (FIRs) of the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+ ions were investigated to evaluate the optical temperature sensing behaviors of NaYb(MoO4)2:Er3+. Importantly, the distinctions of optical temperature sensing behaviors between phosphor and single-crystal state samples were analyzed. The results suggest that stoichiometric NaYb(MoO4)2:Er3+, especially for single-crystal state NaYb(MoO4)2:Er3+, hold great promise as FIR-based optical temperature sensors. In addition, the results can also open up the research interests for employing stoichiometric materials and single crystal materials as optical thermometry applications.

Synthesis, characterization and enhanced photoluminescence and temperature dependence of ZrO2:Dy3+ phosphors upon incorporation of K+ ions

This study reports the successful synthesis and comprehensive characterization of ZrO2:Dy3+ phosphors with the incorporation of K+ ions. The introduction of Dy3+ and K+ in the ZrO2 lattice as lanthanide activators demonstrates its potential as an efficient host material. The structural integrity of ZrO2 remains unaltered following the doping process. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of Zr-O and O-H stretching, along with H2O bending modes in the phosphor sample. The wide luminescence band seen at 460 nm is attributed to luminescence defects in the ZrO2 induced by oxygen, and the presence of water molecules. Photoluminescence (PL) spectra analysis reveals pronounced emission peaks at 491 and 578 nm, corresponding to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions, respectively, upon excitation at 349 nm. Optimizing the Dy3+ doping concentration to 0.4 wt% and achieving a critical distance of 31.82 Å resulted in efficient energy transfer. Notably, co-doping K+ as a charge compensator significantly enhances the luminescence intensity. Moreover, at lower temperatures, direct excitation of Dy3+ ions through our pump wavelength, coupled with exciton-mediated energy transfer, leads to a remarkable increase in PL intensity. Tailoring the doping concentrations effectively shifts the emission spectrum of the phosphor mixture, aligning with the standard white light illumination coordinates (0.333, 0.333). This property positions the material as a promising candidate for applications in white light-emitting diodes (WLEDs) and various high-quality lighting applications. The enhanced photoluminescence and temperature dependence observed in ZrO2:Dy3+ phosphors upon the incorporation of K+ ions pave the way for their potential utilization in advanced luminescent devices.

Synthesis and photoluminescence characterisation of Ca2La2O5:Eu3+, a novel red-emitting phosphor: a comprehensive study

ABSTRACT A novel low-melting-temperature chemical flux method was used to synthesise a Ca2La2O5 lattice doped with Eu3+ ions in the range of 0.5-2.5 mol-%. The phosphors were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, particle size distribution, photoluminescence (PL), and Fourier transform infrared spectroscopy, respectively. The PXRD pattern revealed the hexagonal crystal structure with the space group P63/m. The microstrain (ϵ) was found to not vary with different concentrations of dopant and the negative means compression in the lattice. Particles of varying sizes and irregular shapes were observed from the SEM micrographs. The EDAX mapping revealed that all the constituent elements were found to be in appropriate ratios. Interestingly, the Ca2La2O5:xEu3+ (x = 0.5-2.5 mol-%) phosphor samples were excited at 590 nm, showing a Stokes-shifted red-PL with significant intensities at 615 and 627 nm. Unconventionally, when the phosphor is excited at 590 nm, the Eu3+ ion-characteristic luminescence owing to 5D0→7FJ (J = 0, 1, 2, 3, 4) transitions are manifested. Another remarkable observation is that the PL at 627 nm corresponding to 5D0→7F3 transition was much stronger than the 615 nm emission of Eu3+ corresponding to 5D0→7F3 transition, indicating high colour purity among the available red-emitting phosphors.

Novel intense blue emitting Bi2Zr2O7:Ce3+ nanocomposites insertion into flexible polymer films for anti-counterfeiting, long-term storage fingerprints, and display device applications

The development of multifunctional organic/inorganic hybrid materials for anti-counterfeiting and food packaging applications can be achieved through the use of polymer nanocomposites containing poly(vinyl alcohol) (PVA) and chitosan (CS), as well as Ce3+-activated Bi2Zr2O7 nanocomposites (PCBC NCs). However, synthetic methods for these nanocomposites are often time- and energy-intensive, leading to heterogeneous films that require compatibilizers to disperse the organic matrix's inorganic nanoparticles (NPs). This study used a simple solution casting approach to impregnate the appropriate phosphor sample into PVA-CS (PC) flexible films, resulting in luminous ink for high-security anti-counterfeiting applications. Using this nanocomposite ink offers an even higher level of security, as the prints can be submerged in copper chloride (CuCl2) aqueous solutions to quench the luminous message. The masked fingerprints used for long-term storage (up to 12 months) exhibit stable level 1–3 ridge features with high contrast and sensitivity, which may improve printing quality and performance in the fight against counterfeiting. In addition, a mathematical model implemented in Python-based software was used to investigate the latent fingerprints of level 1–2 ridge features.

Study on the structure and luminescence properties of a novel Li3Sc2(PO4)3: Eu3+ orange-red emission phosphor for wLEDs

The manufacture of high-efficiency and stable red phosphor is the key to solve the matter of high color temperature and poor color rendering of commercial white light-emitting diodes (wLEDs). In this work, a series of Li3Sc2-x(PO4)3: xEu3+ (x = 0–0.4) phosphor samples were prepared by conventional solid-phase reaction. The structure and optical properties of Li3Sc2(PO4)3: Eu3+ are investigated. When the doping amount of Eu3+ is 0.3 mol, phosphors have the highest luminescence intensity. The temperature-dependent characteristics of the prepared phosphors are studied. The combined emission intensity at 423K is 77.4% of that at 298K, showing significant thermal stability. Finally, the prepared Li3Sc2(PO4)3 phosphor package is tested in the LED device. The results of the color temperature of 5423K, as well as color rendering index (CRI) (Ra = 81.6) and color coordinate CIE (0.3343, 0.3471), are satisfactory, suggesting that this red phosphor has potential for wLEDs applications.

Synthesis, characterization and thermoluminescence properties of MgB4O7 phosphor co-doped with Tm and Dy

The luminescent and dosimetric properties of the MgB4O7 phosphor co-doped with Tm and Dy ions (MgB4O7:Tm,Dy) obtained by the solution combustion technique were investigated. With the prepared material, sintered dosimeters in pellet form were made. The MgB4O7 dosimeters doped with Tm and Dy with 0.25 and 0.10 mol% respectively and sintered at 1223 K for 3 h showed a sensitivity almost 11 times greater than the sensitivity of the TLD-100 commercial dosimeter. The TL response as a function of the gamma dose showed linearity up to 50 Gy followed by a supralinearity region and, above 500 Gy, the saturation region of the electron traps is reached. The fading of the main TL peak was negligible in the first five days after irradiation reaching 13% after 60 days and the lower detection limit was 43 μGy. The kinetic parameters were determined using the deconvolution method revealing general and second order kinetics. The morphology, crystallography and photoluminescence of the prepared phosphor samples are also reported.

Synthesis and photoluminescence of novel blue‐emitting phosphor of Eu2+‐activated fluoroborate BaGaBO3F2

AbstractPure and Eu2+‐activated fluoroborate BaGaBO3F2 was prepared using high‐temperature solid‐state reaction. BaGaBO3F2 is a wide band semiconductor with the indirect transition characteristic. The excitation and luminescence spectra of the phosphor were measured, and it was found that Eu2+‐activated BaGaBO3F2 exhibits a bright blue color under ultraviolet (UV) light. The narrow emission band peaked at 425 nm is attributed to the transitions of 4f65d→4f7(8S7/2), and the Stokes shift estimated for this phosphor sample is 3140 cm−1. The lifetime of the luminescence is also reported. The absolute quantum efficiency (QE) of the phosphor was evaluated, and it was found that the absolute QE decreases with increasing Eu2+ concentration. The phosphor shows an excellent quantum efficiency of 72.5% and a high thermal activation energy of 0.342 eV. The study concludes that Eu2+‐doped BaGaBO3F2 phosphor has promising luminescence application abilities and can be used as a blue‐emitting phosphor in a variety of applications.

Luminescence properties of Tb3+/Eu3+ ions activated LiLaSiO4 phosphors for solid-state lighting and flexible display applications

The synthesis and luminescence properties of Tb3+ and Eu3+ single- and co-doped LiLaSiO4 (LLSO) phosphors with energy transfer mechanisms were reported. The rare-earth ions doped LLSO phosphors were synthesized via a solid-state reaction method and their physical characterizations such as phase purity, surface morphology, and elemental analysis were investigated systematically. For the Tb3+ and Eu3+ single- and co-doped LLSO phosphors, their photoluminescence (PL) properties were studied in detail. The LLSO:Tb3+ and LLSO:Eu3+ single-doped phosphors showed superior red and green emissions due to 5D4→7F5 and 5D0→7F2 in the optimized characteristic electronic transitions under ultraviolet (UV) irradiation, respectively. The luminescence performances for both the LLSO:Tb3+ and LLSO:Eu3+ phosphors were optimized at 0.125 mol of doping ion concentration. Under UV excitation, by adjusting the Eu3+ ion concentration in LLSO:0.125Tb3+/Eu3+ phosphors, the tunable emissions from green to red via yellow-orange were obtained. Thus, the tunable emission spectra and luminescence decay lifetimes with increasing the doping content of acceptor ions (Eu3+) confirmed an efficient energy transfer from Tb3+ to Eu3+ ions in the co-doped samples. The critical distance between Tb3+ and Eu3+ was determined to be 13.26 Å and the energy transfer mechanism from Tb3+ to Eu3+ ions was demonstrated to be a dipole-dipole mechanism interaction. In addition, the temperature-dependent PL study was carried out for the LLSO:0.125Tb3+/0.025Eu3+ co-doped phosphor sample and it showed better thermal stability against the temperature quenching. The Tb3+ and Eu3+ single- and co-doped LLSO/polydimethylsiloxane (PDMS) flexible composite films were fabricated by mixing the phosphor powders and PDMS solution. Benefiting from the effective protection of the PDMS matrix, the luminescence stability of the composite films was greatly enhanced. Based on the excellent properties of the synthesized phosphors, Tb3+ and Eu3+ single-doped and Tb3+/Eu3+ co-doped LLSO phosphors could serve as a single-phase multicolor-emitting phosphor under UV excitations.

Wide colour tunability through cross relaxation and energy transfer in a Eu3+/Tb3+:ZnGa2O4 phosphor

In this article, the Tb3+, Eu3+ activated/co-activated ZnGa2O4 phosphors were synthesized using solid state reaction method to study the structural and optical characteristics. The XRD and SEM techniques, were used to study the crystallinity, phase purity and particles size whereas the EDS measurement approved the existence of different elements present in the phosphor samples. The FTIR and diffuse reflectance spectra of phosphor samples were studied to know the phonon frequency and the optical band gap. The PLem spectra of Tb3+ activated ZnGa2O4 phosphor contain blue, green and orange red emissions on 378 nm excitation. A colour tunability from blue to green regions was seen to arise due to cross relaxation on increasing the concentrations of Tb3+ ion. The Eu3+ activated ZnGa2O4 phosphor exhibited a strong red emission under 393 nm excitation. Further, the Eu3+ activated ZnGa2O4:Tb3+ phosphor showed colour tunability from blue to bluish white and from green to red under 260 and 378 nm excitations, respectively. Moreover, an energy-transfer (ET) has been observed from Tb3+ to Eu3+ ions with energy transfer mechanism as dipole-dipole interaction. The ET efficiency for 0.8 mol% Eu3+ in ZnGa2O4:0.05 Tb3+ phosphor has been found 97%. Under 260 nm excitation, the Eu3+/Tb3+ co-activated ZnGa2O4 phosphor also emits blue, green and red bands. Thus, the Tb3+, Eu3+ co-activated ZnGa2O4 phosphor may be useful for solid-state lighting applications.

A novel multifunctional double perovskite structure phosphor La2MgTiO6:Mn4+, Eu3+

A series of La2MgTiO6: Mn4+ and La2MgTiO6: Mn4+, Eu3+ phosphors were prepared by high-temperature solid-phase method. The emission spectra of La2MgTiO6: Mn4+, Eu3+ phosphor samples under 328 nm excitation overlap with the absorbing regions of plant phytochromes PR and PFR in the far red and near infrared double wavelength range. The temperature-dependent and wavelength-dependent emission spectra show that the two distinguishable emission peaks of Eu3+ and Mn4+ exhibit clearly different temperature and wavelength responses. Thus, dual-emission optical sensing based on changes in the fluorescence intensity ratio(FIR) of Mn4+ and Eu3+ ions, the relative sensitivity of wavelength detection in the range of 288–348 nm maxima is 8.13% nm−1 at 288 nm, and relative sensitivity of optical temperature sensing in the range of 298–498 K maxima is 2.09% K−1 at 498 K, In this study, La2MgTiO6: Mn4+, Eu3+ phosphor samples with very promising optical properties can provide the possibility of application in multiple fields.

Cation substitution induced highly symmetric crystal structure in cyan-green-emitting Ca2La1-xLuxHf2Al3O12:Ce3+ solid-solution phosphors with enhanced photoluminescence emission and thermal stability: Toward full-visible-spectrum white LEDs

Highly efficient cyan-green-emitting phosphors are urgently needed for high-color-quality full-visible-spectrum white light-emitting diodes (LEDs). Herein, we report on efficient near-ultraviolet-excited cyan-green-emitting Ca2La1-xLuxHf2Al3O12:Ce3+ (CLa1-xLuxHA:Ce3+) garnet phosphors, which are developed based on the solid-solution design of chemical cation substitution. All phosphor samples present a garnet crystal structure with the Ia3‾d space group; with increasing Lu3+ ions content, the lattice could be gradually contracted, along with a high symmetry as well as rigidity. Furthermore, under the 408 nm excitation, the cyan-green emissions of CLa1-xLuxHA:Ce3+ phosphors are progressively enhanced with a slight blue-shift, due to crystal field splitting and Stokes shift. Importantly, quantum efficiency and thermal stability performances are greatly improved by introducing smaller Lu3+ ions to replace the bigger La3+ ions, owing to the high rigidity structure with high symmetry. The optimized CLa0.5Lu0.5HA:Ce3+ phosphor exhibits an intense cyan-green emission band with high internal quantum efficiency of 76.4% and external quantum efficiency of 54.4%. Through employing the as-prepared CLa0.5Lu0.5HA:Ce3+ cyan-green phosphor, we have successfully fabricated a full-visible-spectrum LED device, demonstrating a bright warm-white light emission with an extremely high color rendering index (Ra = 98.0, R9 = 95.9, and R12 = 94.3) and low correlated color temperature (3497 K) under 100 mA driving current. This study not only reveals the correlation between the crystal structure evolution and luminescent properties of phosphor materials, but also provides new strategies for the design and development of novel efficient luminescent materials for high-quality full-visible-spectrum LED lighting.

Enhanced green up/down-conversion emissions through phase transformation in Ho3+/Yb3+ co-doped Y2O3:ZrO2 phosphors in presence of Na+ ions

This study reports the intense green upconversion and downconversion emissions from Ho3+/Yb3+/Na+ co-doped Y2O3:ZrO2 phosphor prepared by traditional solid-state reaction technique for fixed concentration of Ho3+/Yb3+ ions and different concentrations of Na+ ion. The phosphor samples exhibit a multiphase crystalline structure in the absence of Na+ ions. However, with co-doping of Na+ ions (at 20 mol%), it almost turns into Y4Zr3O12 with single rhombohedral phase. When Na + ions are present in the sample, the SEM image reveals a growth in particle size. The UV–Vis–NIR measurements show an enhancement in the absorbance of doped REs ions (Ho3+/Yb3+) on Na+ co-doping. The Ho3+/Yb3+ co-doped Y2O3:ZrO2 phosphor shows an intense green upconversion (UC) emission at 549 nm due to Ho3+ ions on the excitation with 980 nm radiation. In the presence of Na + ions, a modification of the crystallinity, growth in crystallite size (particle size) and an increase in the asymmetry of the crystalline structure around the REs ions led to an enhancement in the intensity of the UC emission almost about ∼8.5 times. The Log-Log plot demonstrates the involvement of two photons in the UC process. The lifetime of the 5F4/5S2 level decreases with increasing the concentration of Na + ion. Thus, the prepared phosphor could be an excellent candidate for source of green light, finger printing, optoelectronic devices etc.