Order-disorder phase transformations and specific heat of nonstoichiometric vanadium carbide |
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| Authors: | V N Lipatnikov A I Gusev P Ettmeier W Lengauer |
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| Institution: | 1. Institute of Solid-State Chemistry, Ural Branch of the Russian Academy of Sciences, 620219, Ekaterinburg, Russia
2. Institut für Chemische Technologie Anorganischer Stoffe, Technische Universit?t Wien, A-1060, Wien, ?sterreich
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| Abstract: | AbstractA study has been made of the order-disorder phase transformations in the homogeneity region of the VCy nonstoichiometric cubic vanadium carbide (0.66<y<0.88). It has been established that an ordered V6C5 phase with monoclinic (space group C2/m) or trigonal (P31) symmetry, and a cubic (space group P4332) ordered V8C7 phase can form in the VCy carbide below 1450 K, depending on the actual composition. The effect of off-stoichiometry and structural vacancy ordering
on the specific heat of the VCy carbide has been investigated. The temperatures and heats of the reversible order-disorder equilibrium transitions have been
determined. The ordering in the VCy carbide is shown to be a first-order phase transition. An equilibrium diagram of the V-C system taking into account ordering
in the nonstoichiometric vanadium carbide has been constructed.
Fiz. Tverd. Tela (St. Petersburg) 41, 529–536 (March 1999) |
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