Synthesis and Characterization of New Green Oxonitridosilicate Phosphor, (Ba,Eu)3Si6O12N2, for White LED

Abstract

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Understanding Thermal Quenching of Photoluminescence in Oxynitride Phosphors from First Principles

“…There is an additional blue shift of 0.06 eV at 300 K in the emission curve in the case of Ba 3 Si 6 O 12 N 2 :Eu. 7 Figure 2 is then confirmed and completed (in red) by the present first-principles results, as explained later.…”

“…Similar considerations lead us to 5d–4f gaps of 535 nm (2.32 eV) and 485 nm (2.56 eV) for Ba 3 Si 6 O 12 N 2 :Eu and Ba 3 Si 6 O 9 N 4 :Eu, respectively. There is an additional blue shift of 0.06 eV at 300 K in the emission curve in the case of Ba 3 Si 6 O 12 N 2 :Eu Figure is then confirmed and completed (in red) by the present first-principles results, as explained later.…”

“…The experimental absorption and emission spectra as well as their temperature dependence have been measured experimentally 7 and lead to a full width at half-maximum (fwhm) of the two emission curves at 4 K of 1500 and 1300 cm −1 for Ba 3 Si 6 O 12 N 2 :Eu and Ba 3 Si 6 O 9 N 4 :Eu, respectively. These two FWHMs are considered rather narrow and therefore it is expected that the luminescence in both compounds only comes from one luminescent center for each material (one nonequivalent crystallographic position), despite the existence of several Ba inequivalent sites (two in Ba 3 Si 6 O 12 N 2 and three in Ba 3 Si 6 O 9 N 4 ), where substitution by Eu may occur.…”

Comprehensive Band Gap and Electronic Structure Investigations of the Prominent Phosphors M2Si5N8:Eu2+ (M = Ca, Sr, Ba) Determined Using Soft X-ray Spectroscopy and Density Functional Theory

“…Given that the M 2 Si 5 N 8 system is of tremendous industrial relevance, the good agreement between our measurements and calculations, and the relatively simple variation in the band gaps with changes in AE ion, it is well worth trying to establish a larger trend between the X-ray spectroscopy band gaps and those calculated by using the mBJ and GGA potentials. Figure is a plot of calculated versus measured band gaps (using X-ray spectroscopy) of materials with a wide range of band gaps and also similar patterns in their electronic structures. ,,− To survey materials with a wide range of band gaps, both alkaline earth metal nitrides (such as the M 2 Si 5 N 8 phosphors in this study) and early transition metal oxides (here various V 2 O 5 polymorphs) are included. The high covalency between the metal and ligand sites in these compoundsthat they all follow the trend of a VB maximum formed by ligand p-states and a CB minimum formed by metal d-statesmakes their inclusion in the same graph natural.…”

“…Oxo/nitridosilicates and SiAlONs set the benchmark for phosphor-converted light-emitting diodes (pc-LEDs) upon doping with Eu 2+ and Ce 3+ . − Recently, several Mg-nitridosilicates and -nitridoaluminates, as well as the nitridoberyllo­aluminate Sr 2 [BeAl 3 N 5 ]:Eu 2+ , emerged as next-generation highly efficient red-emitting phosphor materials with superior luminescence properties and exceptionally narrow red emission. ,,− Common strategies of preparing nitridosilicates are by bottom-up syntheses using high temperatures. But novel ways of synthesis methods for M 2 Si 5 N 8 :Eu 2+ phosphors and their effect on the crystal structure and luminescence properties are the subject of thorough investigations. , Just recently, the postsynthetic design of nitridosilicates by ion exchange in metal halides was successful and led to the hitherto unknown but previously predicted alkaline-earth nitridosilicates Mg 2 Si 5 N 8 and β-Ca 2 Si 5 N 8…”