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

The nitridoberylloaluminate Sr-2[BeAl3N5]:Eu2+ 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 degrees C. The crystal structure was solved and refined from single-crystal X-ray diffraction data (P (1) over bar (no. 2), Z = 2, a = 6.061(2), b = 6.982(3), c = 7.872(4) angstrom, alpha = 102.22(3), beta = 112.62(2), and gamma = 104.02(2)degrees). The crystal structure of Sr-2[BeAl3N5]:Eu2+ is made up out of a network of vertex- and edge-sharing AIN, tetrahedra and trigonal-planar BeN3 units. The negative charge is compensated by Sr2+ ions occupying three crystallographic sites. Sr2+ ions are coordinated by seven and eight N atoms, respectively. After irradiation of Eu2+ doped samples with blue light (440-450 nm), strong red luminescence (emission maximum at approximate to 612 nm; full width at half-maximum (fwhm) 65-73 nm (1715-1966 cm(-1)) is observed. Until now, Sr-2[BeAl3N5]: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 redemitting phosphors such as Sr[LiAl3N4]:Eu2+ (SLA), Sr[Li2Al2O2N2]:Eu-2(+) (SALON), Sr-4[LiAl11N14]:Eu-2(+), or Sr[Mg3SiN4]:Eu-2(+) (SMS).