Abstract:White emission produced by Ti-doped MgAl2O4 phosphor powder is reported, which is in contrast to blue emission from most Ti-doped single crystals of MgAl2O4. The white emission peak consists of four deconvoluted peaks: 440, 490, 550, and 620 nm, when was excited by 260 nm wavelength. Ti4+ in octahedral sites was found to contribute mostly to greenish blue emissions at 490 and 550 nm. The red emission at 620 nm was produced by abundant Mg2+ and O2− vacancies in the spinel powder.
“…1b. In contrast, the Ti-doped micron-sized MgAl 2 O 4 of our previous work [12] shows high crystallinity, attributed to the high-temperature treatment of the MgAl 2 O 4 powder (1300 °C for 2 h).Fig. 1
a XRD pattern for Ti-doped nano MgAl 2 O 4 powder synthesized at 500 °C 1 h with reference peaks of MgAl 2 O 4 from JCPDS and b , c TEM images of the powder
…”
Section: Resultsmentioning
confidence: 97%
“…The blue emission of Ti-doped MgAl 2 O 4 single crystals is attributed to Ti 4+ in Al (octahedral) sites, which was the only form of Ti ions in the single crystals [10, 11]. However, Ti-doped MgAl 2 O 4 micron-sized powder was shown to have both Ti 3+ and Ti 4+ equally occupying both Al (octahedral) and Mg (tetrahedral) sites [12]. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…Fig. 2Photoluminescence of Ti-doped MgAl 2 O 4 : a 260 nm excitation, b nano, and c micron [12] powders synthesized at 500 °C, 1 h, and 1300 °C, 2 h, respectively
…”
Section: Resultsmentioning
confidence: 99%
“…Strong blue emission is observed from single crystals of Ti-doped MgAl 2 O 4 ; the disappearance of the red emission is attributed to charge compensation through the addition of Ti 4+ [10, 11]. However, in our previous work, we found that Ti-doped micron-sized MgAl 2 O 4 powder heat-treated in air produced a white emission [12]. The difference was explained via the occurrence of red and green emissions in addition to the blue observed from Ti-doped MgAl 2 O 4 single crystals.…”
Section: Introductionmentioning
confidence: 99%
“…The difference was explained via the occurrence of red and green emissions in addition to the blue observed from Ti-doped MgAl 2 O 4 single crystals. Our previous work [12] also simulated the mechanism for the red emission via intrinsic Schottky defect associate, (V O
·· –V Mg ′′) x . The present work reports the visual observation of extrinsic Schottky defects on the surface of Ti-doped MgAl 2 O 4 nanopowder and relates it to the difference in the emission spectra between micron and nano systems.…”
Ti-doped nano MgAl2O4 for white emission was synthesized by combustion method. Extrinsic Schottky defects, Al vacancies and Ti4+ dopant in Al sites, which are considered to be responsible for bluish-white emission, were observed by STEM on the surface of Ti-doped nano MgAl2O4 powder. The stabilities of the Schottky defect associates, (TiAl
·–VAl′′′)′′, were demonstrated by DFT calculation. The emission behavior was interpreted with these results.
“…1b. In contrast, the Ti-doped micron-sized MgAl 2 O 4 of our previous work [12] shows high crystallinity, attributed to the high-temperature treatment of the MgAl 2 O 4 powder (1300 °C for 2 h).Fig. 1
a XRD pattern for Ti-doped nano MgAl 2 O 4 powder synthesized at 500 °C 1 h with reference peaks of MgAl 2 O 4 from JCPDS and b , c TEM images of the powder
…”
Section: Resultsmentioning
confidence: 97%
“…The blue emission of Ti-doped MgAl 2 O 4 single crystals is attributed to Ti 4+ in Al (octahedral) sites, which was the only form of Ti ions in the single crystals [10, 11]. However, Ti-doped MgAl 2 O 4 micron-sized powder was shown to have both Ti 3+ and Ti 4+ equally occupying both Al (octahedral) and Mg (tetrahedral) sites [12]. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…Fig. 2Photoluminescence of Ti-doped MgAl 2 O 4 : a 260 nm excitation, b nano, and c micron [12] powders synthesized at 500 °C, 1 h, and 1300 °C, 2 h, respectively
…”
Section: Resultsmentioning
confidence: 99%
“…Strong blue emission is observed from single crystals of Ti-doped MgAl 2 O 4 ; the disappearance of the red emission is attributed to charge compensation through the addition of Ti 4+ [10, 11]. However, in our previous work, we found that Ti-doped micron-sized MgAl 2 O 4 powder heat-treated in air produced a white emission [12]. The difference was explained via the occurrence of red and green emissions in addition to the blue observed from Ti-doped MgAl 2 O 4 single crystals.…”
Section: Introductionmentioning
confidence: 99%
“…The difference was explained via the occurrence of red and green emissions in addition to the blue observed from Ti-doped MgAl 2 O 4 single crystals. Our previous work [12] also simulated the mechanism for the red emission via intrinsic Schottky defect associate, (V O
·· –V Mg ′′) x . The present work reports the visual observation of extrinsic Schottky defects on the surface of Ti-doped MgAl 2 O 4 nanopowder and relates it to the difference in the emission spectra between micron and nano systems.…”
Ti-doped nano MgAl2O4 for white emission was synthesized by combustion method. Extrinsic Schottky defects, Al vacancies and Ti4+ dopant in Al sites, which are considered to be responsible for bluish-white emission, were observed by STEM on the surface of Ti-doped nano MgAl2O4 powder. The stabilities of the Schottky defect associates, (TiAl
·–VAl′′′)′′, were demonstrated by DFT calculation. The emission behavior was interpreted with these results.
Aluminum hydroxides are considered to be a potential abundant, low‐cost blue emissive material to construct UV‐pumped white light‐emitting diodes (WLEDs). In this work, a single‐source precursor chemical vapor decomposition method is adapted to fabricate stable, strongly emissive aluminum hydroxide phosphors with photoluminescence quantum yield of up to 69% in solid state by thermal decomposing aluminum diacetate hydroxide (Al(OH)(Ac)2) at temperatures (260–360 °C) in N2 atmosphere. It exhibits layered, amorphous structure and its emission of aluminum hydroxide is enhanced by electron‐donating surface hydroxyl groups and originates from F+ centers and carbon‐related defects contributing to UV (388 nm) and blue (450–520 nm) spectral regions, respectively. Employing the as‐fabricated aluminum hydroxides as blue phosphor and CuInS2 nanocrystals as red phosphor, high color rendering and high‐efficiency WLEDs with luminous efficiencies up to 37 lm W−1 and high color rendering index of 91 are fabricated. This is the best performance reported so far for aluminum hydroxide based LEDs.
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