Corundum (structure)

Corundum is the name for a structure prototype in inorganic solids, derived from the namesake polymorph of aluminum oxide (α-Al₂O₃).^[1] Other compounds, especially among the inorganic solids, exist in corundum structure, either in ambient or other conditions. Corundum structures are associated with metal-insulator transition,^[2] ferroelectricity,^[3] polar magnetism,^[4][5] and magnetoelectric effects.

Structure

The corundum structure has the space group R3c. It typically exists in binary compounds of the type A₂B₃, where A is metallic and B is nonmetallic, including sesquioxides (A₂O₃),^[6] sesquisulfides (A₂S₃),^[7] etc. When A is nonmetallic and B is metallic, the structure becomes the antiphase of corundum, called the anticorundum structure type,^[8] with examples including β-Ca₃N₂^[9] and borates. Ternary and multinary compounds can also exists in the corundum structure. The corundum-like structure with the composition A₂BB'O₆ is called double corundum.^[4] A list of examples are tabulated below.

Crystal structure of corrundum. The unit cell contains 16 formulas R2W3 (R=red, W=white). Each red atom is surrounded by six white atoms, and each white by four red.

Materials that exist in the corundum structure

Chemical formula	Alternative name	Material type	Reference
Al2O3	α-Al2O3 or corundum	Oxide	[1]
V2O3		Oxide	[2][10]
Cr2O3	α-Cr2O3	Oxide	[10]
Fe2O3	α-Fe2O3 or hematite	Oxide	[10]
Ga2O3	α-Ga2O3	Oxide	[11]
In2O3	rh-In2O3	Oxide	[12][13]
Ti2O3	α-Ti2O3	Oxide	[14]
Mn2O3	ε-Mn2O3	Oxide	[15]
Rh2O3		Oxide	[16]
Ir2O3	α-Ir2O3	Oxide	[17]
Tl2O3		Oxide	[18]
Ca3N2	β-Ca3N2	Nitride	[9]
In2S3	ε-In2S3	Sulfide	[19]
Tm2S3	E-Tm2S3 or ε-Tm2S3	Sulfide	[20]
Yb2S3	E-Yb2S3 or ε-Yb2S3	Sulfide	[21]
Lu2S3	E-Lu2S3 or ε-Lu2S3	Sulfide	[22]
Cr2(CN2)3		Carbodiimide	[23]
Yb2(CN2)3		Carbodiimide	[24]
Ca3(BO3)2		Borate	[25]
Sr3(BO3)2		Borate	[26]
Eu3(BO3)2		Borate	[27]
ScFeO3		Ferrite	[28]
GaFeO3		Ferrite	[29]
InFeO3		Ferrite	[30]
CrTiO3		Titanate	[31]
NiCrO3		Chromite	[32]
InVO3		Vanadate	[33]
Ni3TeO6		Double oxide	[34]
Ni2InSbO6		Double oxide	[35]
Ni2ScSbO6		Double oxide	[35]
Mn2FeMoO6		Double oxide	[36]
Mn2FeWO6		Double oxide	[37]
Co4Ta2O9		Triple oxide	[38][39]

See also

• Corundum
• Ilmenite
• Perovskite (structure)