Photoluminescence properties of Eu2+-activated sialon S-phase BaAlSi5O2N7

Within the scope of the search of potential LED conversion phosphors, the photoluminescence properties of Eu2+-activated BaAlSi5O2N7 sialon S-phase have been investigated. It shows a broad emission band in the wavelength range of 400–650 nm with maxima from 483 to 500 nm with increasing the Eu2+ concentration. This short-wavelength emission of Eu2+ despite nitrogen-rich coordination is attributed to lowering of the crystal field strength as a result of long distance between Eu and (N, O) anions. Due to the very rigid T12X18-4 network, T = (Si, Al) and X = (N, O), in the crystal structure of MAlSi5O2N7 (M = Sr, Ba), it is supposed that each Eu ion will create its own preferred local coordination irrespective of the occupation of the other sites by Ba or Sr ions in the MAlSi5O2N7 host lattice, which results in resembling luminescence properties for Eu2+-doped in BaAlSi5O2N7 and SrAlSi5O2N7.