Real Competitors to Ruby: The Triel Oxonitridoborates AlB₄O₆N, Al_0.97Cr_0.03B₄O₆N, and Al_0.83Cr_0.17B₄O₆N

AbstractAlB4O6N, Al0.97Cr0.03B4O6N, and Al0.83Cr0.17B4O6N are the first representatives of the recently established structure‐family of oxonitridoborates containing Al3+. These compounds are isotypic to CrB4O6N and are synthesized in a multi‐anvil press under high‐pressure/high‐temperature conditions of 7.0 GPa/1350 °C. Structural refinement by single‐crystal X‐ray diffraction shows that they crystallize in the space group P63mc (no. 186) with two formula units per cell. Detailed characterization including high‐temperature X‐ray powder diffraction (HT‐XRD), electron probe microanalysis (EPMA), measurements of second harmonic generation (SHG), hardness, photoluminescence properties, vibrational spectroscopy, and band structure calculations reveal intriguing physicochemical properties that strongly resemble the famous material ruby.