Titanium nitride (TiN) is currently used as a structural and functional material in a variety of applications because of its unique properties. First of all, TiN has high hardness, wear and corrosion resistance as well as high thermal stability, which are of crucial importance for protective and decorative coatings. In addition, it is characterized by good diffusion barrier properties, low electrical resistivity, increased optical reflectance and compatibility with complementary metal-oxide-semiconductor (CMOS) processes, that makes it promising for diffusion barrier and gate applications, solar cell 8 and infrared reflector 9,10 applications as well as a coating for electrode materials in lithium-ion batteries. Recently, TiN thin films were also suggested as alternative plasmonic material, exhibiting less loss and providing other practical advantages compared to noble metals. However, easy oxidation of TiN already at temperatures of 500-550 • C, and its inherent brittleness restrict the field of its possible application in extreme thermal and mechanical conditions. An effective method of increasing TiN oxidation resistance is its alloying with aluminum. Since aluminum (as titanium) can form an fcc crystal phase, it substitutes for titanium in the crystal lattice of the nitride. The addition of Al to TiN coatings drastically increases their resistance to oxidation (from 500 • C to 800 • C), and also ensures the preservation of high values of hardness and wear resistance at temperatures up to 900-950 • C. Moreover, due to their variable optical properties TiAlN-based coatings are very promising for photothermal and solar energy applications. However, the necessity to enhance the efficiency of photothermal conversion of concentrating solar collectors claims to increase operating temperature of solar absorbers. For example, in concentrating solar power systems with gas-phase central heat receivers operating temperature can reach 1000 • C. At the same time, annealing above 900 • C results in spinodal decomposition of the metastable supersaturated Ti 1-x Al x N solid solution into TiN-and AlN-rich cubic domains. The metastable fcc AlN domains further transform into a stable hexagonal close packed AlN wurtzite phase with a pronounced volume increase of ∼24%. These structural transformations cause a sharp decrease in hardness of Ti 1-x Al x N as well as generation of microcracks which serve as fast diffusion paths, dramatically decreasing the oxidation resistance of the coatings. Moreover, Ti 1-x Al x N is fully oxidized at 1000 • C. Therefore, over the past two decades intensive efforts have been directed towards finding ways to further improve the characteristics of the Ti-Al-N system.