Traditional High Temperature Solid State Research Articles

Reversible multimode modulations in photochromic transparent Eu3+doped K0.5Na0.5NbO3 based ceramics

Rare-earth doped transparent photochromic materials have attracted extensive attention in applications of optical information storage and optical switching, in which the high transparency and large fluorescence modulation ratio are required. In this work, 0.94 (K0.5Na0.5)NbO3-0.06 (Sr0.5Ba0.5) (Zn1/3Bi2/3)O3: x wt% Eu2O3 ceramics (KNN-SBZB: xEu) with x=0.1, 0.2, 0.3, 0.4 were prepared by traditional high temperature solid state sintering reaction method. High transmittance (T) was achieved due to the small grain size (less than 110 nm) and the highly symmetrical phase structure. High optical transmittance of 69.27 % at 780 nm and 78.24 % at 1100 nm were obtained in the KNN-SBZB: 0.3Eu ceramic, while large luminescence intensity modulation ratio (∆RL) ∼94.9 %, transmittance (∆RT) ∼5.76 % and diffuse reflectivity (∆ABS) ∼12.59 % were achieved in KNN-SBZB: 0.2Eu ceramic (T ∼62.92 % at 780 nm). Additionally, both the transmittance modulation and luminescence intensity modulation of KNN-SBZB: xEu ceramics show good stability after 10 cycles.

Inorganic/organic bilayer--modified CaS:Eu2+,Ce3+ phosphor and luminescent film laminated glass for efficient solar energy utilization

CaS:Eu2+,Ce3+ are widely used in various fields, which is due to their excellent luminescent properties. However, the traditional high-temperature solid state synthesis of CaS has the disadvantage of large particle size and easy agglomeration. Also, the CaS-based material is unstable and decomposes easily in humid air. In the present study, CaS:Eu2+, Ce3+(here denoted as CaS:EuCe) phosphors with a uniform particle size, good dispersion, and small particle size (Dv50 = 13.46 μm, abbreviated as D50) have been obtained using a novel coprecipitation-mesophase decomposition (CMD) method. In addition, the inorganic-organic bilayer modification technology has been used to form core-shell structured CaS:EuCe@CaZnOS@Si69 phosphors, which could resist acidic/basic solutions and moist air. Its surface property changed from hydrophilicity (water contact angle 37.28°) to hydrophobicity (water contact angle 112.23°). Finally, the optimized phosphor was used to prepare luminescent film laminated glass, which showed the potential for use in plant growth. The reaction process of the CaS phosphor, as prepared by the CMD method, and the mechanism of the bilayer surface modification, have here been discussed in detail. We believe that the here-developed synthesis method provides a new strategy for the preparation of high-performance chalcogenide phosphors.

Effect of nano-SiO2 on performances of KBaYSi2O7: Eu3+ red phosphor for NUV-pumped LEDs

KBaY0.9Si2−xSixO7: 0.1Eu3+ phosphors were prepared by traditional high temperature solid state reaction method at 1050 ℃ with nano and micron SiO2 as raw materials. The particle size of nano-SiO2 is 15, 30 and 50 nm. The crystal structure, morphology, luminescence intensity and thermal stability of the samples were characterized by XRD, SEM, photoluminescence spectra and temperature-dependent fluorescence spectra, respectively. The results show that the phosphor is a single matrix, and the mixing of nano-SiO2 increases the particle size and improves crystallization of the phosphor. KBaY0.9Si0.4Si1.6O7: 0.1Eu3+ mixed by nano-SiO2 with particle size of 15 nm has the improved performance of luminescence intensity enhanced by 13.7 % and thermal stability enhanced by 11 %. CIE coordinates are (0.670, 0.330) and close to the standard redlight source. Therefore, KBaY0.9Si0.4Si1.6O7: 0.1Eu3+ has a broad prospect in red phosphors for NUV excited LEDs.

Preparation of novel KAlSiO4: Ce3+ broadband cyan-emitting phosphors via partial cation substitution for applications in white-light LEDs

Broadband cyan-emitting phosphors with strong absorption between 300 and 400 nm are ideal replacements for traditional blue and green phosphors used in commercial light-emitting diodes (LEDs). In this paper, a series of K1-xAlSiO4: xCe3+(x = 0.02–0.06) broadband cyan phosphors were prepared using the traditional high-temperature solid state method and the cation un-equivalent substitution strategy. It was found that the KAlSiO4 matrix has a monoclinic structure with high symmetry. The experimental and theoretical optical band gaps of the host were 5.6 eV and 4.86 eV, respectively. After doping with Ce3+, strong absorption was observed in the near ultraviolet region. The optimum Ce3+ doping concentration in the host was 0.04 as indicated by the strongest observed emission intensity. The full width at half maximum of the emission spectra of the series of samples are all greater than 120 nm and covered the blue and green wavelength ranges (370–600 nm). The luminous intensity of the K0·96AlSiO4: 0.04Ce3+phosphor at 150 °C was 91.1% of that at room temperature, and the Gaussian peak of the emission spectrum slightly broadened. These results were also combination with theoretical DFT calculations. It was found that the phosphor had very good thermal stability and rigidity. The phosphor was also mixed with a commercial red phosphor, interfaced with a UV chip and packaged into an LED. This LED was characterized and had a color rendering index greater than 90 across a broad range of drive currents. This work highlights the utility of the fabricated phosphor as means of simplifying white-light LED fabrication.

Structure, morphology and optical characterization of Sm3+-doped MgGeO3 nanocrystals for warm white light emitting devices

Orange-red emitting Sm[Formula: see text]-doped MgGeO3 phosphors were synthesized by traditional high temperature solid state method. The powders were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), UV-Vis spectrometer and photoluminescence (PL) spectra. XRD, SEM and EDS analysis results revealed that MGO:Sm phosphor samples were successfully synthesized. and the optimum MGO:0.1% mol Sm[Formula: see text] phosphor exhibited good photoluminescence emission intensity, thermal stability, life time and color purity. The diffuse reflectance spectra give the results of sample absorption, reflectance, transmittance and optical band gap. The larger optical band gap is 5.25 eV and the stronger photoluminescence intensity [Formula: see text] when the doping concentration is 0.1[Formula: see text] mol. The dipole–dipole interaction is the main mechanism of the concentration quenching phenomenon. The thermal activation energy of the sample is 0.176 eV, and the life time of the prepared sample can reach 14.76 [Formula: see text]s, due to the correlated color temperature (CCT) of less than 2000 K, the potential application value in warm white light emitting device.

Structural, electrical and photochromic properties of Na0.5Bi4.5Ti4O15:xEr3+ ferroelectric ceramics

In view of the excellent piezoelectric performances of bismuth layered structure ferroelectrics at high temperature, Na0.5Bi4.5Ti4O15:xEr3+ ceramics have been successfully manufactured by the traditional high temperature solid state method. The influence of additive (Er3+) concentration on the phase structure, morphology and electrical properties of ceramics has been investigated. After Er3+ ion introduction, the ferroelectric properties are palpably enhanced, and the 2Pr reaches 30 μC/cm2 at x = 0.004. Furthermore, the ferroelectric domain structure of ceramics was characterized by PFM for the first time. Meanwhile, a reversible photochromic (PC) reaction and the associated luminescence modulation are achieved. It is found that a higher ΔIdec of 83.6% is obtained using down-conversion (DC) mode than up-conversion (UC) one. More importantly, an additional exposure to natural light can further enhance the ΔIdec from 73% to 80.5% after 407 nm irradiation. The present investigation suggests that the modified NBT ceramics with multiple performances facilitate the development of multifunctional materials used in electric devices, anti-counterfeiting and information storage.

Excellent upconversion luminescence and temperature sensing performance of CdMoO4:Er3+,Yb3+ phosphors.

In this paper, Er3+/Yb3+ co-doped CdMoO4 phosphors were prepared by a traditional high temperature solid state reaction method. Based on the 3D network structure of the CdMoO4 host and the efficient Er3+/Yb3+ upconversion luminescence combinations, excellent green emission properties were observed when the prepared sample is irradiated with a laser at about 980 nm. For optical temperature sensors based on the fluorescence intensity ratio (FIR), the prepared phosphors have excellent sensitivity to temperature in the range of 293 to 473 K. With increasing environmental temperatures, the absolute sensitivity of the CdMoO4:0.02Er3+,0.08Yb3+ sample reached a maximum at about 473 K (Sa = 1.388% K-1). The calculated relative sensitivity of the optical temperature sensor was Sr = 1.631% K-1 at 293 K. This is due to the sensitive thermally coupled energy levels (TCLs) of the Er3+ ions (2H11/2 and 4S3/2) in the CdMoO4 structure. Therefore, it is shown that the prepared CdMoO4:0.02Er3+,0.08Yb3+ phosphor has excellent applications in non-contact optical temperature measurement.

Synthesis and luminescence properties of NaBaPO4:Tm3+,Dy3+ white-light emitting phosphors with enhanced brightness by Li+ co-doping

In this paper, a series of NaBaPO4:Tm3+, Dy3+, Li+ (NBPO) single-doped and co-doped phosphors were synthesized successfully by the traditional high-temperature solid state reaction method. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and fluorescent decay curves. The XRD results showed that samples NaBaPO4: Tm3+, Dy3+ were matched well with the standard profile NaBaPO4.White light emission can be achieved by simply adjusting the doping concentration of Tm3+ and Dy3+ ions in NaBaPO4 host. The CIE coordinates (0.3192,0.2951) of phosphor NBPO: 0.01 Tm3+, 0.04Dy3+ was closest to the coordinates of ideal white light. The enhanced emission intensity was achieved by doping Li+ ions. When the Li+ ions doping concentration was 0.01, the emission intensity reached the maximum, which was 2.2 times the emission intensity of the non-doped Li + phosphor. The results demonstrated the promising application of NaBaPO4: Tm3+, Dy3+, Li+ phosphor for near-UV white LEDs.

Preparation of a Novel Red Y2MoSiO8: Eu3+, Dy3+ Phosphor

A novel Eu3+ ion-doped and Dy3+ ion-doped yttrium silicomolybdic (Y2MoSiO8) phosphor was prepared by traditional high temperature solid state reaction at 1200°C. The Y2MoSiO8 monodoped Eu3+ phosphors were excited at 395nm, the peak emission of red light is at 618nm and 595nm. The concentration of Eu3+ ions affects the emission intensity of the fluorescent substance. Y2MoSiO8: Eu3+, Dy3+ phosphors excited at 370 and 395nm, it can emit red light at peaks of 617nm and 611nm, respectively, widen the absorption band of Eu3+ in single doping, and improve the luminous intensity. This phosphor has the advantages of simple preparation, high luminous efficiency and easy industrialization.

Design, synthesis and photoluminescence properties of a new orange-red phosphor K3BiTaP3O13:Sm3+

In this work, a series of K 3 Bi 1- x TaP 3 O 13 : x Sm 3+ ( x = 0.02–0.12) phosphors were synthesized using traditional high-temperature solid state reaction and their photoluminescence properties were studied. With 403 nm light excitation, three main peaks at 560–570 nm, 596–608 nm and 643–651 nm appeared, due to the 4 f →4 f characteristic transition of Sm 3+ . The best concentration of Sm 3+ ions doping is x = 0.06, and further increasing Sm 3+ will decrease the emission intensity because of concentration quenching effect. The decay curves of K 3 Bi 1- x TaP 3 O 13 : x Sm 3+ were recorded, showing decreasing luminescent lifetimes with increasing Sm 3+ concentrations. The CIE coordinates of K 3 Bi 0.94 TaP 3 O 13 :0.06Sm 3+ were (0.5515, 0.4455) corresponding to orange-red color. Furthermore, the phosphor had good thermal stability, retaining 86.9 % intensity at 200 ℃ of that at 25 °C. These results indicate that K 3 Bi 1- x P 3 O 13 : x Sm 3+ is a good orange-red phosphor for LED applications.

Thermally stable Na2ZrO3: Eu3+ phosphors for UV excited tricolor white LEDs

Researches are going on to promote a highly thermally stable and efficient phosphor material for the red component of the tri-color white LEDs. Herein, Eu3+ activated Na2ZrO3 phosphors were designed through the traditional high temperature solid state reaction method. The structural studies such as crystallinity, phase purity and surface morphology of the prepared samples were examined from the powder XRD and FE-SEM techniques. The photoluminescence study illustrates that the phosphor can be excited through the charge transfer band and the characteristic excitation wavelength of Eu3+ ions. The emission spectra present pure red emission, resulting from the prominent peak at 608 nm ascribe to the 5D0 → 7F2 transition of Eu3+ ions. Temperature dependent PL and lifetime measurement from 300 K to 475 K with an interval of 25 K were employed to get a deeper insight into the thermal stability of the phosphor. The emission intensity goes on decreasing with an increase in temperature. The activation energy of thermal quenching estimated from the Arrhenius plot is found to be 0.195 eV. Almost 60% of the initial intensity at room temperature is still maintained above 200 °C and the CIE coordinates also remain stable at the higher temperature. The average lifetime of the excited state of Eu3+ ions varied from 0.74 ms to 0.71 ms within the observed temperature range. The above results point out that the aforementioned sample shows good thermal stability and it can be applied as the red emitting phosphor for wLED, operated in the high temperature region.

A novel Al3+ modified Li6CaLa2Sb2O12:Mn4+ far-red-emitting phosphor with garnet structure for plant cultivation

A novel-far red emission Li6CaLa2Sb2O12 (LCLSO):Mn4+ phosphor was prepared by traditional high temperature solid state reaction method. The morphology, spectral characteristics and luminescence properties of the phosphors were all studied systematically. Based on the results, when x = 0.0045 (x represents the doping concentration of Mn4+), the emission intensity of LCLSO:xMn4+ phosphor reaches the maximum, and the concentration quenching occurs after the Mn4+ doping concentration exceeds 0.0045. In addition, the effect of Al3+-doped on the luminescent properties of the materials was also studied. The optimum doping concentration of Al3+ is y = 0.009 (y represents the doping concentration of Al3+), and the luminescence intensity of Mn4+ can be increased about 4 times. Moreover, the integrated luminescence intensity, the thermal activation energy, and decay time can be obtained via calculation. In summary, LCLSO:Mn4+, Al3+ phosphor exhibits good luminescence efficiency and thermal stability, and possesses the latent application foreground in plant growth lighting.

Mn4+ doped tetratungstate Sr9Gd2W4O24 far-red phosphor: Synthesis, luminescence properties, and potential applications in indoor plant cultivation

The red oxide phosphors activated by Mn4+ have become a research hotspot because of their excellent physical/chemical stability, which can be applied in the field of light-emitting diodes (LED) plant growth lighting. Here, a new type of Sr9Gd2W4O24 (SGWO):Mn4+ red phosphor was prepared by traditional high temperature solid state reaction method. The phase compositions and morphologies of powders were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The luminescent properties of the samples with varying Mn4+ concentrations were investigated, and the photoluminescence excitation (PLE) spectra illustrate that samples can be effectively excited by near-ultraviolet/blue light. Furthermore, typical concentration quenching occurs when the doping concentration of Mn4+ exceeds 0.4 mol%. In addition, the thermal activation energy of the sample was calculated to be 0.3641 eV. Importantly, under the excitation of near-UV light at 365 nm, SGWO:0.004Mn4+ phosphor can emit bright far-red light. All the results indicated that SGWO:Mn4+ phosphors have potential application value in indoor plant cultivation.

NaLa2SbO6:Mn4+ far-red phosphor: Synthesis, luminescence properties and emission enhancement by Al3+ ions

A novel far-red emission NaLa2SbO6(NLSO):Mn4+ phosphor was prepared by traditional high temperature solid state reaction method. In the range of 200–600 nm, NLSO:Mn4+ phosphors exhibit broad excitation band centered at 322 nm and 498 nm. Under the excitation of 322 nm, the phosphor exhibits a far-red emission band centered at 707 nm in the range of 600–800 nm. In NLSO:Mn4+ phosphors, the optimum doping concentration is x = 0.003. In addition, the effect of Al3+-doped on the luminescent properties of the materials was also studied. The optimum doping concentration of Al3+ is x = 0.004, and the luminescence intensity of Mn4+ can be increased by 53%. In addition, NLSO:0.003Mn4+, 0.004Al3+ phosphors have high internal quantum efficiency and good thermal stability. The CIE chromaticity coordinates of NLSO:0.003Mn4+, yAl3+ phosphors are calculated, and which are located in the far-red region. All the results show that the synthesized phosphors have great application prospects in plant cultivation.

Tunable luminescence properties of Ba2ScTaO6:Bi3+, Eu3+ phosphors

A series of Bi3+/Eu3+ single-doped and co-doped Ba2ScTaO6 phosphors was prepared by traditional high-temperature solid state reaction method. Their structure and photoluminescence properties of the samples were systematically studied by X-ray diffraction (XRD) analysis, scanning electron microscopy, excitation and emission spectra, and decay curves. The observation of XRD patterns shows that all samples are pure phases. Under the UV excitation, the emission color of Ba2ScTaO6:Bi3+, Eu3+ can be tuned by Bi3+/Eu3+ ratio change from amaranth to orange–red, which is realized by Bi3+–Eu3+ energy transfer. In addition, the energy transfer mechanism, luminescence decay curves and chromaticity coordinates are discussed in detail. The results show that Ba2ScTaO6:Bi3+, Eu3+ is a promising red phosphor for white light-emitting diodes.

Vibrational spectroscopy and microwave dielectric properties of AY2Si3O10 (A=Sr, Ba) ceramics for 5G applications

AY2Si3O10 (A = Sr, Ba) trisilicate ceramics were synthesized by traditional high temperature solid state reaction method. X-ray diffraction patterns and Rietveld refinement revealed that AY2Si3O10 (A = Sr, Ba) ceramics belonged to triclinic and monoclinic crystal systems with Pī and P21/m space groups, respectively. The vibrational modes of [SiO4] tetrahedra, [YO6] octahedra and [(Sr/Ba)O8] polyhedra were analyzed by Raman spectroscopy. The infrared spectroscopy fitting analysis was used to determine intrinsic dielectric properties. Excellent microwave dielectric properties were measured for SrY2Si3O10 and BaY2Si3O10 with ɛr = 9.3, Qf = 64100 GHz, τf = −31 ppm/°C and ɛr = 9.5, Qf = 65600 GHz, τf = −28 ppm/°C, respectively. Both trisilicate ceramics are considered potential candidates for 5G and mm wave technology, provided τf can be further tuned.

Preparation and luminescent properties of tunable polychromatic phosphors CaNaB5O9: RE3+(RE = Dy, Eu, Tb)

A series of CaNaB5O9: RE3+ (RE = Dy, Eu, Tb, Tb/Eu, Dy/Eu) phosphors were prepared by the traditional high temperature solid state method. The crystal structure, morphology and luminous properties were characterized by powder X-ray diffraction, scanning electron microscopy and fluorescence spectra, respectively. The influence of rare earth ion doping concentration on the luminescence performance of samples was discussed. The optimal doping concentrations of Dy3+, Eu3+ and Tb3+ were 1 mol%, 15 mol% and 5 mol%, respectively. Under certain wavelength excitation, the samples CaNaB5O9: Dy3+, CaNaB5O9: Eu3+ and CaNaB5O9: Tb3+ can emit white light, red light and green light respectively. Under the near ultraviolet excitation of 369 nm, Ca1-x-yNaB5O9: xTb3+, yEu3+ phosphors can effectively transfer the excitation energy from Tb3+ to Eu3+. The luminous color changes gradually from green to yellow. Under the excitation of 393 nm, the emission spectra of CaNaB5O9: Dy3+, Eu3+ phosphors show the typical transition emission of Dy3+ and Eu3+. The red emission from energy transition of Eu3+ adds red light to the white emission of Dy3+ and decrease the color temperature. The results show that the sample CaNaB5O9: RE3+ (RE = Dy, Eu, Tb) can be the candidates of color-tunable phosphors for W-LEDs.

Synthesis and photoluminescence properties of a novel Ca2LaNbO6:Mn4+ double perovskite phosphor for plant growth LEDs

In this paper, a series of Ca2LaNbO6 (CLN):Mn4+ far-red phosphors with different doping concentration were successfully prepared by traditional high temperature solid state method at 1250 °C. The samples were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra, ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), temperature-dependent emission spectra and internal quantum efficiency (IQE). The particle size of CLN is < 3 μm. The strongest excitation peak of CLN:Mn4+ phosphors lies at 352 nm, which is attributed to the 4A2g → 2T2g transition of Mn4+ ions. The sample has a strong emission peak at 684 nm, which corresponds to the 2Eg → 4A2g energy level transition of Mn4+ ions. The optimum doping concentration of the sample is 0.03 mol%, and the quenching mechanism is dipole–quadrupole interaction. In addition, the thermal activation energy of the sample was calculated to be 0.368 eV. Importantly, under the excitation of near-ultraviolet light at 365 nm and driven by 25 mA current, the LED with CLN:0.0003Mn4+ emits bright far-red light. All the results indicated that CLN:Mn4+ phosphors have potential application value in indoor plant cultivation.

Luminescence properties and energy transfer investigations of Ce3+ and Tb3+ co-doped NaCaGaSi2O7 phosphors

The NaCaGaSi2O7:Ce3+、NaCaGaSi2O7:Tb3+ and NaCaGaSi2O7:Ce3+/Tb3+ phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by X-ray diffraction (XRD), fluorescent decay times, photoluminescence (PL) emission and excitation spectra including temperature-dependent PL properties. The effects of Ce3+ singly doped and Ce3+/Tb3+ co-doped concentrations on the structure, luminescence properties and energy transfer of NaCaGaSi2O7 phosphors were studied in detail. The results indicated that the energy transfers between Ce3+ and Tb3+ in the host occurred mainly via a dipole-dipole mechanism, and the critical distances of the ion pairs (Rc) were calculated by the quenching concentration method and spectral overlap method. The Ce3+ emission intensity and decay lifetimes decrease with the raise of Tb3+ concentration in NaCaGaSi2O7:Ce3+/Tb3+ samples. The above results indicate that NaCaGaSi2O7:Ce3+/Tb3+ can be a candidate as a host material for solid-state lighting and display fields.

The Enhancement of H2 Evolution over Sr1-1.5xTbxWO4 Solid Solution under Ultraviolet Light Irradiation.

In this work, Sr1−1.5xTbxWO4 (0 ≤ x ≤ 0.2) solid solutions were synthesized via a traditional high-temperature solid state method. Le Bail fitting on the powder X-ray diffraction (XRD) pattern showed that these solid solutions are pure phase. Scanning electron microscopy showed that the SrWO4 and Sr0.82Tb0.12WO4 samples are composed of micrometer particles and submicron crystallites, respectively. Ultraviolet–visible diffuse reflectance spectra suggested that the bandgaps of Sr1−1.5xTbxWO4 are narrower than the undoped sample. The Sr0.82Tb0.12WO4 sample, with the assistance of 1.5 wt % Ru-cocatalyst, exhibits the best performance for H2 evolution in 5 vol % aqueous triethanolamine (TEOA), which results in about 6.1 and 2.8 times efficiency improvement compared with the intrinsic SrWO4 in methanol and aqueous TEOA, respectively. All the photocatalysts recycled after the photocatalytic reactions showed no degradation when checked by powder XRD.