Illuminating Nitridoberylloaluminates: The Highly Efficient Red-Emitting Phosphor Sr2[BeAl3N5]:Eu2+

The nitridoberylloaluminate Sr 2 [BeAl 3 N 5 ]:Eu 2+ was obtained through reaction of the binary nitrides in a hot isostatic press (HIP) under a pressure of 50 MPa N 2 and a temperature of 1400 °C. The crystal structure was solved and refined from single-crystal X-ray diffraction data ( P 1̅ (no. 2), Z = 2, a = 6.061(2), b = 6.982(3), c = 7.872(4) Å, α = 102.22(3), β = 112.62(2), and γ = 104.02(2)°). The crystal structure of Sr 2 [BeAl 3 N 5 ]:Eu 2+ is made up out of a network of vertex- and edge-sharing AlN 4 tetrahedra and trigonal-planar BeN 3 units. The negative charge is compensated by Sr 2+ ions occupying three crystallographic sites. Sr 2+ ions are coordinated by seven and eight N atoms, respectively. After irradiation of Eu 2+ doped samples with blue light (440–450 nm), strong red luminescence (emission maximum at ≈612 nm; full width at half-maximum (fwhm) 65–73 nm (1715–1966 cm –1 ) is observed. Until now, Sr 2 [BeAl 3 N 5 ]:Eu 2+ is the only member of a compound class containing only beryllium and aluminum as network building atoms in a nitride, contributing to the range of red-emitting phosphors such as Sr[LiAl 3 N 4 ]:Eu 2+ (SLA), Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ (SALON), Sr 4 [LiAl 11 N 14 ]:Eu 2+, or Sr[Mg 3 SiN 4 ]:Eu 2+ (SMS).