Recent achievements in single crystal growth of actinide compounds

Abstract

Important progress has been achieved in solid state physics of the element uranium since large and perfect single crystals of uranium metal and compounds are available. To allow similar progress in the solid state physics of the other actinide elements, a large effort has been undertaken at the European Institute for Transuranium Elements to grow single crystals of actinide compounds with cubic crystal structure like the dioxides, the monopnictides, the monochalcogenides, and some intermetallic compounds. The single crystals enable the measurement of physical properties related to the electronic structure in order to extend the knowledge of chemical bonding in the 5 f transition elements. The different steps allowing the preparation of actinide samples for solid state physics investigations are: • preparation of actinide metals • refining of actinide metals • preparation of compounds by direct synthesis between the elements of the highest available purity • crystal growth • characterization, orientation and encapsulation of the single crystals Actinide dioxides. Actinide dioxide single crystals are obtained by chemical vapour transport (UO 2, NpO 2) using TeCl 4 as transporting agent or by high temperature solution growth with lead vanadate as solvent (ThO 2, NpO 2, PuO 2). Actinide monopnictides. Actinide monopnictide single crystals are grown by the mineralisation technique. Large single crystals (up to 1 2 cm 3 of PuAs, PuSb, PuBi were prepared. Actinide intermetallic compounds. Pulling from the levitated melt in a Hukin crucible by the Czochralski technique allows the preparation of intermetallic compound single crystals (AnX 3 or Laves phases). A single crystal of PuFe 2 (θ 4 mm, 1 = 5 cm) was prepared.