7 research outputs found
Aluminate red phosphor in light-emitting diodes : theoretical calculations, charge varieties and high-pressure luminescence analysis
This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 104-2113-M- 002-012-MY3 and MOST 104-2923-M-002-007-MY3). This research was also supported by National Centre for Re- search and Development, Poland (Grant No. PL- TW2/8/2015).Searching for a non-rare earth-based oxide red-emitting phosphor is crucial for phosphor-converted light- emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited Sr4Al14O25:Mn phosphor exhibiting red emission peaked at ~653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of Sr4Al14O25:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of Sr4Al14O25 were analyzed by density functional theory calculation using the hybrid exchange- correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman 27Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent on the luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial β-SiAlON:Eu2+ green phosphor, and Sr4Al14O25:Mn red phosphor were evaluated for commercial applications: using the present Sr4Al14O25:Mn red phosphor converted LED as backlighting source.PostprintPeer reviewe
Interface-engineered resistive switching in Ag/SrTiO
For Ag/Nd0.7Ca0.3MnO3/YBa2Cu3O7 (Ag/NCMO/YBCO) heterostructures, we investigate effects of an SrTiO3 (STO) buffer layer inserted into the Ag/NCMO interface upon the room-temperature resistive switching. In comparison with the non-buffered (Ag/NCMO/YBCO) structure, the insertion of the STO buffer layer can greatly enhance the electric-field-induced-resistance (EPIR) effect. The STO-buffered (Ag/STO/NCMO/ YBCO) device can be switched on-and-off between the higher to lower resistance states at an EPIR ratio of 253% with pulsed voltage  ±1.5 V and 405% with pulsed voltage  ±3.0 V. The enhanced EPIR ratio is attributed to a combined effect of the migration of oxygen vacancies near the interface and ferroelectric polarization of the STO buffer
Narrow Red Emission Band Fluoride Phosphor KNaSiF<sub>6</sub>:Mn<sup>4+</sup> for Warm White Light-Emitting Diodes
Red
phosphors AMF<sub>6</sub>:Mn<sup>4+</sup> (A = Na, K, Cs, Ba,
Rb; M = Si, Ti, Ge) have been widely studied due to the narrow red
emission bands around 630 nm. The different emission of the zero-phonon
line (ZPL) may affect the color rendering index of white light-emitting
diodes (WLED). The primary reason behind the emergence and intensity
of ZPL, taking KNaSiF<sub>6</sub>:Mn<sup>4+</sup> as an example, was
investigated here. The effects of pressure on crystal structure and
luminescence were determined experimentally and theoretically. The
increase of band gap, red shift of emission spectrum and blue shift
of excitation spectrum were observed with higher applied pressure.
The angles of ∠FMnF and ∠FMFÂ(M = Si, Ti, Ge) were found
clearly distorted from 180° in MF<sub>6</sub><sup>2–</sup> octahedron with strong ZPL intensity. The larger distorted SiF<sub>6</sub><sup>2–</sup> octahedron, the stronger ZPL intensity.
This research provides a new perspective to address the ZPL intensity
problem of the hexafluorosilicate phosphors caused by crystal distortion
and pressure-dependence of the luminescence. The efficacy of the device
featuring from Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup> (YAG) and KNaSiF<sub>6</sub>:Mn<sup>4+</sup> phosphor was 118 lm/W
with the color temperature of 3455 K. These results reveal that KNaSiF<sub>6</sub>:Mn<sup>4+</sup> presents good luminescent properties and
could be a potential candidate material for application in back-lighting
systems
Aluminate red phosphor in light-emitting diodes:theoretical calculations, charge varieties and high-pressure luminescence analysis
Searching for a non-rare earth-based oxide red-emitting phosphor is crucial for phosphor-converted light- emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited Sr4Al14O25:Mn phosphor exhibiting red emission peaked at ~653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of Sr4Al14O25:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of Sr4Al14O25 were analyzed by density functional theory calculation using the hybrid exchange- correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman 27Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent on the luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial β-SiAlON:Eu2+ green phosphor, and Sr4Al14O25:Mn red phosphor were evaluated for commercial applications: using the present Sr4Al14O25:Mn red phosphor converted LED as backlighting source