Phase Relations in the Thorium-Nitrogen System

The binary Th-N phase diagram is illustrated in Fig. 2. Two equilibrium compounds are indicated, ThN [1] with a NaCl-type crystal structure [2] and Th3N4 [3] recently designated as a-Th3N4 [4] with a trigonal structure [5]. 

The Th-N phase diagram, drawn by the authors of this article. 

The various sources of data are as follows the Th(l)-ThN two-phase region data are 

Th-ThN Region. Nitrogen dissolves in metallic Th raising the temperature of the allotropic transformation, a-Th- p-Th, from 1365 to 1605 20°C where the solubility in a-Th is 7.4 0.2% N [6]. The temperature dependence of the N solubility in a-Th has been measured by Gerds, Mallett [7] and is given by the equation 

The melting point of pure p-Th metal, 1754 15°C, is increased by N additions [1,8] to a peritectic point at 1800 25°C [6]. The peritectic reaction on cooling is 

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