New Ta3Ве Phase in the Film Coatings of Tantalum–Beryllium Alloys

Resumo

Ta–Be solid-solution–alloys have been obtained for the first time by ion-plasma sputtering and co-deposition of ultradispersed Ta and Be particles in the range of concentrations of Be from 1.1 to 85.8 at % in the film, which is a confirmation of the thermofluctuation melting and coalescence of small particles. A regular character of changes of the unit-cell volume of the solid solution of Be in β-Ta has been established. Upon the vacuum annealing at 800°C of a sample with Be concentration at a level of 26.8 at %, there was a new phase, identified as Ta₃Be, with a tetragonal face-centered lattice with p arameters a = 0.7579 ± 0.0003 nm and c = 0.7370 ± 0.0005 nm. The X-ray diffraction data for the identification of this intermetallic compound are given. The performed electron-microscopic investigations have shown that the thermal expansion coefficient of the Ta₃Be phase is greater than that of the solid solution of Be in β-Ta. The study of the temperature dependence of the electrical resistance of the Ta₃Be phase upon cooling from room temperature to 10 K has shown that this phase has a metallic character of the R(T) dependence. The Ta₃Be phase does not possess superconducting properties down to 10 K.