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 Eu 2+ activated phosphor of Ca 5 Si 2 Al 2 N 8 has been successfully synthesized by the solid-state reaction at the constant pressure. The crystal structure has been refined using the Rietveld refinement. The Ca 5 Si 2 Al 2 N 8 crystallizes in Orthorhombic with lattice parameters of a  = 9.2336 (12) A, b  = 6.1317 (8) A, c  = 15.5049 (20) A and V  = 877.85 (31) A 3 , respectively. The special polyhedrons of [Al 2 N 6 ] and [Si 2 N 6 ] built up by the edge shared SiN 4 and AlN 4 tetrahedrons have been found in the Ca 5 Si 2 Al 2 N 8 , and the Al and Si ions are arranged in the separated sites. The three Ca 2+ sites with the coordination number of six, seven and eight provide suitable sites for Eu 2+ ions to occupy. The luminescence spectra of Eu 2+ doped Ca 5 Si 2 Al 2 N 8 show that a red light with the peak at 643 nm (FWHM ≈ 92 nm) can be observed, and the broad excitation band ranges from 350 nm to 565 nm. The excellent thermal stability has also been detected, which shows that the intensity at 150 °C is still beyond 90% of the initial intensity.