The thermodynamic properties of zirconium nitride are presented, including the phase diagram of the Zr—N system, homogeneity region, temperature and composition corresponding to congruent melting of ZrN_x, enthalpy of formation, as well as electronic structure and chemical bond in zirconium nitride. An equation is given approximating the temperature dependence of the heat capacity of crystalline ZrN in the temperature range of 298.15—3970 K. Temperature dependences of specific heat and electrical resistance of liquid zirconium nitride of the composition 0.9ZrN+0.1ZrO₂ (up to 4500 K) measured by heating with a microsecond current pulse are presented. The main practical significance of these results is that ZrN serves as an inert matrix for mixed nitride fuel (U, Zr)N and (Pu, Zr)N for fast neutron reactors.

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Keywords: nuclear fuel matrices, zirconium nitride, phase diagrams, solid phases, melting, liquid state, enthalpy of formation, enthalpy, specific heat, electrical resistance, temperature measurement, pulsed current heating method PACS: 05.70.−a, 64.70.D−, 65.40.−b (all) DOI: 10.3367/UFNe.2024.02.039654 URL: https://ufn.ru/en/articles/2024/10/d/ Citation: Aristova N M, Onufriev S V, Savvatimskiy A I "Thermodynamic properties of zirconium nitride in the condensed state" Phys. Usp. 67 (10) (2024) Received: 4th, October 2023, revised: 28th, January 2024, accepted: 27th, February 2024 Оригинал: Аристова Н М, Онуфриев С В, Савватимский А И «Термодинамические свойства нитрида циркония в конденсированном состоянии» УФН 194 1082–1094 (2024); DOI: 10.3367/UFNr.2024.02.039654