Highly Robust Oxynitride Phosphor against Thermal Oxidization and Hydrolysis

Abstract

In the development of novel phosphors for various applications, chemical stability was usually neglected. However, the chemical stability of phosphors is strongly relevant to the lifetime and power limit of lighting devices. Here, we report Sr 2 Al 3 Si 7 ON 13 :Ce 3+ , a potential green-emitting candidate for lighting application with high chemical stability against thermal oxidization and hydrolysis. The Sr 2 Al 3 Si 7 ON 13 :Ce 3+ phosphor retained almost the same emission intensity after 800 °C heat treatment in air and water immersion for 5 days. DFT calculation revealed that electrons disperse continuously through the crystal framework, which is a symbol of high covalence and strong bonding. Such a highly condensed cross-linking structure may be responsible for preventing nitride from oxidization. Benefiting from the disordering O/N and Al/Si coordinate environment, Sr 2 Al 3 Si 7 ON 13 :Ce 3+ gave a broad green emission (fwhm = 124 nm), in favor of a high color rendering index (CRI) for light-emitting diode (LED) devices. Using Sr 2 Al 3 Si 7 ON 13 :Ce 3+ , a prototype of a white LED of CRI = 91 was made to demonstrate this point.

Improved Thermal and Chemical Stability of Oxynitride Phosphor from Facile Chemical Synthesis for Vehicle Cornering Lights

“…With the help of DFT calculations, and previous research, [20] the distributions of Al 3+ /Si 4+ , and O 2− /N 3− were determined by comparing the total energies of multi‐configurations for further calculations (Al 3+ in B2, B6, B8, and B9; O 2− in X9, and X14. For details see the Supporting Information, Table S3) [16,20] . The elemental composition of SrAl 2 Si 3 ON 6 by energy dispersive spectroscopy (EDS) (Figure S3) and X‐ray photoelectron spectroscopy (XPS) (Figure S4) is presented in Table S4.…”

“…The integrated intensity of SrAlSi 4 N 7 :Ce 3+ at 150 °C was 79 % of that at 25 °C (denoted by 79 %@150 °C) [15] . The oxynitride iso‐structure SrAl 3/2 Si 7/2 O 1/2 N 13/2 :Ce 3+ gave green emission with improved thermal stability of 84 %@150 °C [16] …”

“…[15] The oxynitride iso-structure SrAl 3/2 Si 7/2 O 1/2 N 13/2 :Ce 3 + gave green emission with improved thermal stability of 84 %@150 °C. [16] Orange-red emission can be obtained by doping Eu 2 + . Orange-red emitting SrAlSi 4 N 7 :Eu 2 + exhibited considerable thermal stability of 85 %@150 °C.…”

Li2Ba4Al2Ta2N8O, the First Barium Nitridoalumotantalate with BCT‐Zeolite Type Structure

“…Wen and Kakihana (2020) showed that the compound Sr 2 Al 3 Si 7 ON 13 : Ce 3+ is very stable against thermal oxidization and water immersion due to the highly condensed cross‐linked covalent [(Al,Si)(O,N) 4 ] framework [19] . The anionic framework of Sr 2 Al 3 Si 7 ON 13 is formed by corner‐sharing [(Al,Si)(O,N) 4 ] and edge‐sharing [Al(O,N) 4 ] tetrahedra, resulting in a degree of condensation of κ=∼0.7, which is defined by the ratio of tetrahedral centers to the coordinating anions (κ=n( T )/n(N,O)).…”

“…Wen and Kakihana (2020) showed that the compound Sr 2 Al 3 Si 7 ON 13 : Ce 3 + is very stable against thermal oxidization and water immersion due to the highly condensed cross-linked covalent [(Al,Si)(O,N) 4 ] framework. [19] The anionic framework of Sr 2 Al 3 Si 7 ON 13 is formed by corner-sharing [(Al,Si)(O,N) 4 ] and edge-sharing [Al(O,N) 4 ] tetrahedra, resulting in a degree of condensation of k = ~0.7, which is defined by the ratio of tetrahedral centers to the coordinating anions (k = n(T)/n(N,O)). Additionally, they could show, based on difference electron density (DED) calculations, that 2-3 covalent bonds were formed from O/N to Al/Si, which ends up in a highly covalent cross-linked framework of [(Al,Si)(O,N) 4 ] tetrahedra.…”