Eu 2+ ‐doped strontium aluminum silicon nitrides having α‐SiAlON and polytypoid structures

Yellow single crystals of aluminum silicon nitrides containing strontium and europium were prepared by heating starting mixtures of Sr 3 N 2 , Si 3 N 4 , AlN, and EuN at 2050°C and 0.85 MPa of N 2 for 8 hours. Single‐crystal X‐ray diffraction revealed that prismatic crystals 20‐100 μm in size were Sr 0.31 Al 0.62 Si 11.38 N 16 :Eu (trigonal, a =7.7937(2) Å, c =5.6519(2) Å, space group P 31 c ), which are isotypic with Sr‐α‐SiAlON, Sr m /2 Al m + n Si 12− m − n N 16− n O n , with m =0.62 and n =0. The Eu 2+ content was approximately 1 at.% of Sr contained in the framework of corner‐sharing (Al/Si)N 4 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, Sr 2.97 Eu 0.03 Al 6 Si 24 N 40 . 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 Sr 0.31 Al 0.62 Si 11.38 N 16 :Eu and Sr 2.97 Eu 0.03 Al 6 Si 24 N 40 were 583 nm and 87 nm, and 584 nm and 91 nm, respectively, under 400 nm wavelength light excitation at room temperature.