Yellow single crystals of aluminum silicon nitrides containing strontium and europium were prepared by heating starting mixtures of Sr3N2, Si3N4, AlN, and EuN at 2050°C and 0.85 MPa of N2 for 8 hours. Single-crystal X-ray diffraction revealed that prismatic crystals 20-100 μm in size were Sr0.31Al0.62Si11.38N16:Eu (trigonal, a=7.7937(2) Å, c=5.6519(2) Å, space group P31c), which are isotypic with Sr-α-SiAlON, Srm/2Alm+nSi12−m−nN16−nOn, with m=0.62 and n=0. The Eu2+ content was approximately 1 at.% of Sr contained in the framework of corner-sharing (Al/Si)N4 tetrahedra with an occupancy of 0.154(2). Block-shaped crystals with a side length of 50-300 μm were a new polytypoid of Sr-α-SiAlON, Sr2.97Eu0.03Al6Si24N40. Streak lines were observed in the direction of the c* axis in the X-ray oscillation photographs, indicating stacking faults of the structure. The fundamental X-ray reflections were indexed with a hexagonal cell (a=7.9489(3) Å, c=14.3941(6) Å). The structure was analyzed with a model of space group P6 in which one of the six Al/Si sites was statistically split into two sites with occupancies of 0.673(5) and 0.227(5). The atomic arrangements in the layers of the structure were similar to those of Sr-α-SiAlON, but the stacking sequences of the layers were different. The peak wavelengths and full widths at half maximum of emission spectra measured for the single crystals of Sr0.31Al0.62Si11.38N16:Eu and Sr2.97Eu0.03Al6Si24N40 were 583 nm and 87 nm, and 584 nm and 91 nm, respectively, under 400 nm wavelength light excitation at room temperature.
- phosphors and luminescent materials
- single crystals
- X-ray diffraction