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Enhanced crystallinity and thermal stability of Ba2+ and Al3+–O2− co-substituted Sr2Si5N8:Eu2+

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Abstract

By co-substituting a cation (M2+: Ba2+ or Ca2+) and Al3+–O2− into Sr2Si5N8:Eu2+ in a solid-state method, we successfully synthesized the nitrido-alumino-silicate phosphors Sr(2−y)MySi5−xAlxN8−xOx:Eu2+ (Ba-AlO-258 (My = Ba0.3, x > 0) and Ca-AlO-258 (My = Ca0.3, x > 0)), which were compared with conventional AlO-258 (y = 0, x > 0), Ba-258 (My = Ba0.3, x = 0), Ca-258 (My = Ca0.3, x = 0), and 258 (y = 0, x = 0). SEM exhibited that the morphology and particle size were very different between Ba-AlO-258 and the Ca-AlO-258 and AlO-258. The crystallinity was evaluated by determining the lattice strain from the peak-width of the XRD pattern. It was found that the crystallinity of Ba-AlO-258 was much higher than that of Ca-AlO-258 and AlO-258 under the same synthesis conditions. We proposed the significance of a size balance between the ionic part, (Ba, Sr, Ca)–(N, O)n, and covalent part, (Si, Al)–(N, O)4 tetrahedron, where the larger Ba2+ (than Sr2+) matches the larger Al3+ (than Si4+) in crystal 258. The emission peaks of the three phosphors shifted to longer wavelengths with the substitution of Si4+–N3− with Al3+–O2−. The temperature dependency of our new Ba-AlO-258 was the best in all phosphors. We found that the co-substitution of M2+ (Ba2+ or Ca2+) and (AlO)+ improved the temperature dependency, although the conventional single substitution of (AlO)+ made it worse. From the advanced thermo-luminescence measurement (excitation: blue light), the significant improvement of the temperature dependency of the emission at blue excitation was strongly considered due to a continuous supply of the red emission from the electron at the trap center. The new Ba-AlO-258 is believed to be the best blue LED phosphor in the well-known industrial 258 series because of its superior thermal property and crystallinity.

Graphical abstract: Enhanced crystallinity and thermal stability of Ba2+ and Al3+–O2− co-substituted Sr2Si5N8:Eu2+

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Supplementary files

Article information


Submitted
25 Feb 2020
Accepted
09 Jun 2020
First published
11 Jun 2020

J. Mater. Chem. C, 2020, Advance Article
Article type
Paper

Enhanced crystallinity and thermal stability of Ba2+ and Al3+–O2− co-substituted Sr2Si5N8:Eu2+

Z. Li, T. Seto and Y. Wang, J. Mater. Chem. C, 2020, Advance Article , DOI: 10.1039/D0TC00965B

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