Order–disorder transformations and phase equilibria in strongly nonstoichiometric compounds

Neutron Diffraction Study of Hydrogen Thermoemission Phenomenon from Powder Crystals

“…As a result of annealing the dehydrogenated sample disintegrated into disordered solid solution of nitrogen in -Zr − hexagonal  phase (structure of L  3 type) and a cubic -phase (Fig.2e) corresponding to the equilibrium phase diagram of Zr-N system (Gusev, 2001). It should be noted that the annealing of hydrogenous Zr 2 N 0,86 H 0,76 phase under similar conditions does not lead to decay or change of crystal structure.…”

“…Thus, by means of dehydroge-nation of the preliminary hydrogenated sample, three modifications of the oversaturated solid solution ZrN 0.43 which do not exist in the equilibrium phase diagram have been obtained. (Gusev, 2001) reveals that under a hydrogen pressure of 10 5 Pa, all samples, including biphase ones, form the sol. s. -Zr 2 N 0.86 H 0.76 (space group P 3 m1).…”

“…greater than z ideal). Annealing the obtained phase in an evacuated and sealed quartz ampoule at T> 370 0 C results in decay corresponding to the equilibrium phase diagram of the Ti-N system (Gusev, 2001). Lowtemperature vacuum evacuation of hydrogen was also studied in solid soluti-ons TiC 0,45 H 0,90 , TiC 0,45 H 0,64 , and TiC 0.35 H 0.43 (Khidirov et al, 2008).…”

Physical Properties of the NbC Carbide

“…The atoms in this structure have octahedral coordination, and the carbon atoms occupy half of the octahedral interstices of the metallic sub-lattice [3]. At temperatures around 1050°C, there is a order-disorder reaction resulting in a carbide with stoichiometry Nb 6 C 5 and trigonal structure (space group P3 1 ) [3,17,[27][28][29][30][31][32][33][34][35][36]. In this carbide, atomic planes with and without defects are stacked alternately [3].…”

A model for understanding the formation energies of nanolamellar phases in transition metal carbides and nitrides

“…At low non-metal vacancy concentrations (relative to the B1 structure), a vacancy ordered phase can be observed at the chemical composition of M 6 X 5 , where M denotes the metal atoms and X denotes the non-metal atoms [22]. In particular to the carbides, this phase is known to exist in the group VB carbides and is predicted to exist in the IVB carbides, although the exact crystal structure of this phase is still debated [23]. The current literature has not identified any vacancy ordered structures at this composition in the nitrides, however phase diagrams do show the potential to create both metal and nitrogen vacancies in the B1 lattice.…”