Thermodynamic Properties of Li-LiH (LiD, LiT) Systems. The Phase Diagram

Konstantin A. Yakimovich, Tatiana Biryukova

Joint Institute for High Temperatures Russian Academy of Sciences, Moscow, Russia.
The Institute of Informatics Problems, Russian Academy of Sciences, Moscow, Russia.

DOI: 10.4236/ojpc.2012.23019                

Abstract

The paper presents a comprehensive critical review and detailed analysis of the literature, published in the field of the phase diagram solution Li-LiH (LiD, LiT). Special attention is paid to the completeness of the source information on the paper’s topic resulting in an extended reference list. Particularly, paper reviews rarely used sources including little-known publications from research centers, proceedings of the international scientific meetings and dissertations. These publications were more thoroughly analyzed in order to make the information available to the scientific society.

Keywords

Diagram; Phase Equilibrium; Lithium Hydride; Deuteride

1. Introduction

The phase diagram of the Li-LiH system is complex. Many investigators have studied its individual parts by different methods such as plotting thermograms, analysis of the electrical resistance as a function of temperature and composition of the solution, and measurement of the partial pressure of hydrogen or of its isotopes when the condensed phase is in equilibrium with the vapor. These studies have identified several systematic features in the phase diagram of the Li-LiH system.

2. The Phase Diagram

The temperature-composition diagram for the systems under consideration is shown schematically in Figure 1 (x is the mole fraction of lithium hydride in the condensed phase). The α-phase (on the left-hand side), which is enriched with lithium, is arbitrarily distinguished from the β-phase (on the right-hand side), which is enriched with hydride. The subscript l or s denotes the liquid or the solid phase, respectively. This system has eutectic properties at point с as well as monotectic properties (the line dfg).

Above the monotectic temperature, the liquid phase has a broad immiscibility zone. Experimental data show that the boundaries of the immiscibility zone (the curve dkf) are essentially the same for the Li-LiH and Li-LiD systems. At the same time, the experiment shows that the position of point с with respect to temperature and concentration is slightly different in these systems.

The characteristic points in the diagram for a Li-LiH system according to [1-3] are given in Table 1 (the concentrations at points f and g are rough estimates).

Figure 2 shows the behavior of the isotherms in the pressure-composition diagram of the Li-LiH system above the temperature of the monotectic. The concentration

Conflicts of Interest

The authors declare no conflicts of interest.

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