Actinoidmetal Boron Carbides

Abstract

The constitution i.e. the phase equilibria of the ternary systems: actinoid metal (Th,U,Pu,Np) — boron — carbon has been investigated by X-ray diffraction and metallographic techniques as well as by melting point analysis, and phase relations have been established in isothermal sections. Phase equilibria are generally characterized by the formation of several high melting ternary compounds and by incompatibility of the actinoid carbides with boron or boroncarbide. Employing X-ray single crystal, powder X-ray and neutron diffraction techniques most of the ternary boroncarbide structures have been established. Classification of these structure types closely follows the general rules for metal borides and carbides. In some cases extended homogeneous regions have been observed with replacement of boron by carbon atoms. Sensitivity against moisture increases with increasing carbon content of the compound and carbon-rich boroncarbides are decomposing as fast as actinoid carbide materials.

Magnetism was particularly investigated in case of the uranium compounds revealing ferromagnetic and/or paramagnetic behavior in accordance to the distance dependent exchange interactions (Hill plot).