Bonding, Lattice Parameter, Density and Defect Structure of TiN Containing an Excess of N
From combustion analyses (TiN → TiO 2), Kjeldahl N-determinations, and gas analyses, it was found that the composition of the titanium nitride used was Ti 0.904±0.010 N, which agreed very well with that obtained by the lattice parameter and density method. From its chemical behavior (dissolution in HF with NH 4 + formation in the presence of oxidizers, especially KMnO 4, and N 2-production at elevated temperatures) and furthermore, from the heats of formation, lattice energy, hardness and high melting point, the conclusion is drawn that the bonding in the nitride is of a mixed type. It appears to be predominantly ionic and to some extent metallic. The partially metallic character of the bonding is evidenced in the release of N 2 during heating, and accounts for the high electrical conductivity and magnetic properties of the nitride. Since the N atoms do not accept all the available valence electrons (from Ti) the radius of the N-anions is smaller than found for N 3-. Using Pauling's formula and a ligancy of 5, a value of r = 1.426 Å is obtained for N. With this value and r = 0.69 Å (for Ti 3+, a lattice parameter α = 4.232 Å is calculated in reasonable agreement with the experimental value a = 4.23986 ± 0.00007Å. The thermal expansion coefficient α 25 is 5.71 × 10 -6 ° C -1 (between 10 and 65° C). The experimental density d 25 is 4.975 ± 0.004 g cm -3 (X-ray density, 5.394 g cm -3). There are 4.94% vacancies in the cationic and 0.175% vacancies in the anionic sublattice of all the sites, 8 per unit cell, of the nitride. © 1967.
M. E. Straumanis et al., "Bonding, Lattice Parameter, Density and Defect Structure of TiN Containing an Excess of N," Acta Metallurgica Sinica (English Letters), Elsevier, Jan 1967.
The definitive version is available at https://doi.org/10.1016/0001-6160(67)90156-3
Materials Science and Engineering
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© 1967 Elsevier, All rights reserved.