Eu2+-activated Ca5Si2Al2N8 – A novel nitridoalumosilicate red phosphor containing the special polyhedron of separated corner-shared [Al2N6] and [Si2N6

Abstract

In this work, a novel nitride based Eu2+ activated phosphor of Ca5Si2Al2N8 has been successfully synthesized by the solid-state reaction at the constant pressure. The crystal structure has been refined using the Rietveld refinement. The Ca5Si2Al2N8 crystallizes in Orthorhombic with lattice parameters of a=9.2336(12)Å, b=6.1317(8)Å, c=15.5049(20)Å and V=877.85(31)Å3, respectively. The special polyhedrons of [Al2N6] and [Si2N6] built up by the edge shared SiN4 and AlN4 tetrahedrons have been found in the Ca5Si2Al2N8, and the Al and Si ions are arranged in the separated sites. The three Ca2+ sites with the coordination number of six, seven and eight provide suitable sites for Eu2+ ions to occupy. The luminescence spectra of Eu2+ doped Ca5Si2Al2N8 show that a red light with the peak at 643nm (FWHM≈92nm) can be observed, and the broad excitation band ranges from 350nm to 565nm. The excellent thermal stability has also been detected, which shows that the intensity at 150°C is still beyond 90% of the initial intensity.