Tantalum nitride (TaN) is a chemical compound that consists of tantalum and nitrogen. It is known for its high hardness, wear resistance, and thermal stability, which makes it a popular material for various applications, particularly in the fields of coatings for cutting tools, decorative coatings, and diffusion barriers in microelectronics. The crystal structure of tantalum nitride plays a critical role in determining these properties.

The crystal structure of TaN can vary depending on the synthesis conditions and the ratio of tantalum to nitrogen. Several different phases of tantalum nitride have been identified, each with unique structural characteristics. The crystal structure of tantalum nitrides is examined by X-ray and electron diffraction techniques and the following seven phases are identified: TaN～0.05 (cubic, β-phase), Ta2N (hexagonal, γ-phase), δ-TaN (hexagonal), ε-TaN (hexagonal), Ta5N6 (hexagonal), Ta4N5 (tetragonal) and Ta3N5 (tetragonal or monoclinic). Thin films of Ta nitrides for electron diffraction study were prepared by nitriding thin evaporated films of tantalum in ammonia and nitrogen. By heating thin films of Ta3N5 in vacuum, the phase transformations occur successively as follows: Ta3N5→Ta4N5→Ta5N6→ε-TaN→Ta2N.

References:

[1] TERAO N. Structure of Tantalum Nitrides[J]. Japanese Journal of Applied Physics, 1971. DOI:10.1143/JJAP.10.248.