Phase-selective synthesis of lead-free CsMnBr3 and Cs3MnBr5 nanocrystals dependent on solvent concentration.

We demonstrate the crystal phase-selective synthesis for lead-free cesium manganese bromine perovskite nanocrystals synthesized by the modified hot-injection method due to changing the concentration of solvent (trioctylphosphine; TOP). The compositions synthesized were determined by the amount of TOP solvent, and the structure phase of the nanocrystals was selected from hexagonal CsMnBr3 to tetragonal Cs3MnBr5 as the amount of TOP solvent increased. The emission peaks of CsMnBr3 and Cs3MnBr5 nanocrystals were observed at 650 nm (red) and 520 nm (green), respectively. After a durability test at 85°C and 85% humidity for 24 h, the lead-free perovskite CsMnBr3 nanocrystal powder maintained its initial emission intensity, and the metal halide Cs3MnBr5 nanocrystal powder exhibited an increase in red emission due to the post-synthesis of CsMnBr3 nanocrystals.

Eu3+-doped Bi2MoO6 phosphors for highly sensitive and visible H2S gas indicator material: optical and color properties, and gas sensing performance.

Bi2MoO6:Eu3+ phosphors were synthesized by a solid state reaction, and H2S gas sensing performance was investigated. The Bi2MoO6:Eu3+ phosphors showed an excellent red emission due to f-f transition of Eu3+. Owing to the exposure to H2S gas, the emission intensity of the phosphors dramatically decreased to 40% of the initial value. The body color of the phosphor changed from yellow-white to dark brown. The response of the Bi2MoO6:Eu3+ phosphors for H2S gas was started from 10 ppm, and the emission intensity exponentially decreased with increasing the concentration until 500 ppm.

Enhancement of the optical properties of CsPbBr3 perovskite nanocrystals using three different solvents.

Green-emitting CsPbBr3 perovskite nanocrystals were synthesized by the modified hot-injection method using three different solvents. The produced nanocrystals showed a narrow green emission band centered at 515-520 nm with full width at half-maximum (FWHM) values of approximately 18-20 nm. The highest photoluminescence quantum yield (PLQY) was obtained for the nanocrystal sample synthesized using a paraffin liquid solvent, with a value of 70.1% under excitation at 450 nm. The CsPbBr3 nanocrystals film light-emitting diodes (LED) chip module showed a luminous efficacy of 40.7lm/Wrad. The white LED (WLED) with green CsPbBr3 and red CsPbI3 nanocrystal films emitted bluish-white light with a high color rendering index of 89, and the luminous efficacy of the WLED reached 16.3lm/Wrad.

Development of high luminous efficacy red-emitting phosphor-in-glass for high-power LED lighting systems using our original low Tg and Ts glass.

Red-emitting phosphor-in-glass (PiG) materials with a high luminescence efficiency were developed by co-firing commercial red-emitting (Sr,Ca)AlSiN3:Eu2+ (SCASN) phosphor and our original glass frits with a composition of Li2O-Na2O-ZnO-Al2O3-B2O3-P2O5, which has a low Tg (271°C) and Ts (380°C) temperatures. By optimizing the sintering temperature and the content of the phosphor, the highest luminous efficacy was obtained for the 3 wt.% SCASN-based PiG sintered at 400°C, which showed a luminous efficacy of 25 lm/W rad by combining the PiG materials with a blue light-emitting diode (LED) chip-on-board (COB, incident power = 100 mA). The internal quantum efficiency of this sample under excitation at 450 nm was 53%. The PiG-based LED maintained a high luminous efficacy when the incident power of the blue COB increased up to 5.5 W (47 lm).

Development of NaY9Si6O26:Yb3+ phosphors with high thermal stability for NIR anti-counterfeiting: study of its crystal structure and luminescent properties.

Near-infrared (NIR) radiation has generated considerable industrial and research interest. However, NIR phosphors for this are limited by low quantum efficiency and broad spectra. Rare-earth-containing compounds doped with activators as host systems for NIR phosphors may resolve these limitations. Yb3+-doped NaY9Si6O26 phosphors were synthesized using a conventional solid-state reaction method. The main phase of the synthesized phosphor samples exhibited a hexagonal structure NaY9Si6O26 phase, and had an angular-shape with an average grain size of 1-3 µm. The NaY9Si6O26:Yb3+ phosphors showed a near-infrared emission from 950 to 1100 nm, which was attributed to the 2F5/2 → 2F7/2 transition of Yb3+ ions under 270 and 920 nm excitation. The excitation spectra, recorded by monitoring the emission at 985 nm, showed two bands in the ultraviolet and infrared regions, which correspond to the charge transfer transition and the 2F7/2 → 2F5/2 transition of Yb3+ ions. At 300 °C, the emission intensity of the NaY9Si6O26:Yb3+ phosphor remained constant at 82%. Furthermore, the thermal degradation was negligible after cooling, suggesting the possibility of application in advanced anti-counterfeiting applications.

Development of a cyan blue-emitting Ba3La2(BO3)4:Ce3+,Tb3+ phosphor for use in dental glazing materials: color tunable emission and energy transfer.

The Ce3+/Tb3+ doped Ba3La2(BO3)4 phosphors were synthesized by a conventional solid state reaction method. The synthesized phosphor samples are a single phase of Ba3La2(BO3)4 and showed angular-shaped fine grains with average particle size from 5 µm to 10 µm. The Ba3La2(BO3)4:Ce3+ phosphors showed an asymmetric broad blue emission under excitation at 365 nm and the Ba3La2(BO3)4:Tb3+ phosphors exhibited typical green emission assigned to the 4f-4f transition of Tb3+ under excitation at 254 nm. Under near-UV (365 nm) excitation, Ba3La2(BO3)4:Ce3+,Tb3+ phosphors showed both a blue emission band and green emission peaks due to Ce3+ and Tb3+, respectively. By optimizing the composition, cyan-blue emission with high color purity (CIE chromaticity coordinate values x = 0.2557 and y = 0.3839) was obtained for the Ba3La2(BO3)4:0.05Ce3+,0.03Tb3+ phosphor, and the internal quantum efficiency of the phosphor at the excitation wavelength of 365 nm is estimated to be 50%. The dental glazing paste prepared by mixing organic binder, Ba3La2(BO3)4:Ce3+,Tb3+ phosphors, and low T g glass was successfully vitrified when it was heated at 600 and 700 °C, and showed high chemical stability of the luminescence properties in acidic aqueous solution (pH = 4).

Effect of α-Al2O3 Particle Size in a Slurry on the Physical Properties of Chemically Strengthened Thin Glass Prepared by the Spray Method.

Chemical strengthening is considered as the most suitable method for strengthening thin glass sheets used in mobile phones. The spray method of chemical strengthening requires a slurry to be sprayed on the glass sample to be strengthened. This slurry is prepared by mixing various compounds. In this study, the influence of α-Al2O3 particle size in the slurry on the physical properties of the chemically strengthened glass prepared by the spray method was investigated. The compressive stress (CS) was dramatically enhanced as the particle size of Al2O3 in the slurry decreased. The glass sample with 13 nm α-Al2O3 including the KNO3-Al2O3 slurry exhibited the highest CS of 905 MPa, and the depth-of-layer (DOL) of this sample was 37 µm. The same slurry composition also achieved the highest bending strength of 640 MPa under different heat treatment conditions. The optimization of the heat treatment conditions, such as temperature and time duration, resulted in the highest value of CS (916 MPa) obtained for the sample heated at 400 °C for 1.5 h, and the maximum DOL (65 µm) was obtained for the sample at 480 °C for 4 h.

Single Crystal Growth and Crystal Structure Analysis of Novel Orange-Red Emission Pure Nitride CaAl2Si4N8:Eu2+ Phosphor.

Single crystal of novel orange-red emission CaAl2Si4N8:Eu2+ phosphor was grown by our original vapor phase technique, and the precise crystal structure was investigated for the first time by single crystal X-ray diffraction analysis. The crystal structure of CaAl2Si4N8:Eu2+ single crystal was verified to be an α-Si3N4-type trigonal structure (space group P31c) with a = 0.79525(9) nm, c = 0.57712(8) nm, and z = 2. The Ca atoms were coordinated to seven nitrogen atoms and located in the three-dimensional framework formed by (Al, Si)N4 tetrahedra. The single-crystal CaAl2Si4N8:Eu2+ phosphors exhibited a broad reddish-yellow emission with a peak at 600 nm under near-UV and blue light excitation. When increasing the temperature up to 150 °C, the emission intensity of the CaAl2Si4N8:Eu2+ phosphor decreased to 88% of the initial value at 25 °C.

Rare-earth-free white emitting Ba2TiP2O9 phosphor: revealing its crystal structure and photoluminescence properties.

A high intensity bluish-white emitting Ba2TiP2O9 phosphor was synthesized by a conventional solid-state reaction method and the precise crystal structure was investigated for the first time by Rietveld refinement analysis. Ba2TiP2O9 has a monoclinic crystal structure with a space group C2/c (no. 15), which is built out of PO4 tetrahedra and TiO5 pyramidal polyhedra connected to form a chain structure along the c-axis. The emission of Ba2TiP2O9 is due to a charge transfer transition between Ti(4+)-O(2-) in the pyramidal TiO5. The obtained Ba2TiP2O9 was excited efficiently by UV and VUV and displayed a bright bluish-white luminescence.