Inverse‐Tunable Red Luminescence and Electronic Properties of Nitridoberylloaluminates Sr(2−x )Ba( x )[BeAl(3)N(5)]:Eu(2+) (x=0–2)

The nitridoberylloaluminate Ba(2)[BeAl(3)N(5)]:Eu(2+) and solid solutions Sr(2−x )Ba( x )[BeAl(3)N(5)]:Eu(2+) (x=0.5, 1.0, 1.5) were synthesized in a hot isostatic press (HIP) under 50 MPa N(2) atmosphere at 1200 °C. Ba(2)[BeAl(3)N(5)]:Eu(2+) crystallizes in triclinic space group [Formula: see text] (no. 2) (Z=2, a=6.1869(10), b=7.1736(13), c=8.0391(14) Å, α=102.754(8), β=112.032(6), γ=104.765(7)°), which was determined from single‐crystal X‐ray diffraction data. The lattice parameters of the solid solution series have been obtained from Rietveld refinements and show a nearly linear dependence on the atomic ratio Sr : Ba. The electronic properties and the band gaps of M (2)[BeAl(3)N(5)] (M=Sr, Ba) have been investigated by a combination of soft X‐ray spectroscopy and density functional theory (DFT) calculations. Upon irradiation with blue light (440–450 nm), the nitridoberylloaluminates exhibit intense orange to red luminescence, which can be tuned between 610 and 656 nm (fwhm=1922–2025 cm(−1) (72–87 nm)). In contrast to the usual trend, the substitution of the smaller Sr(2+) by larger Ba(2+) leads to an inverse‐tunable luminescence to higher wavelengths. Low‐temperature luminescence measurements have been performed to exclude anomalous emission.