STUDY OF THE PHASE AND IMPURITY COMPOSITION OF PD—BA AND PT—BA CATHODE ALLOYS

We have  studied the  phase and  impurity composition of Pd—Ba  and  Pt—Ba cathode alloys obtained on an A 535.02TO arc melting plant using a technology developed by AO Shokin NPP Istok. The study  showed that  the  concentration of detrimental impurities (C; Zn; Cu; Al) in the specimens is within the allowed range. Pd—Ba tapes are rich in Ba but this does not compromise their quality. We have confirmed the earlier found domination of two−phase composition in Pd—Ba and Pt—Ba alloys where  one of the phase is an intermetallic compound (Pd5Ba, Pt5Ba) and the other  is a noble metal(the matrix). The intermetallide is distributed in the  platinum  metal  matrix quite inhomogeneously, this tangibly impairing the operation parameters of cathodes produced from these alloys. For the first time we have shown the high efficiency  of transmission electron microscopy for studying Pd—Ba and  Pt—Ba cathode alloys. We have  for the first time found the Pd2О phase in Pd—Ba. It may significantly reduce the secondary electron emission coefficient and the quality of devices based on this alloy. We have determined the Pd and Pd5Ba grain size in the Pd—Ba alloys and the Pt and Pt5Ba grain size in the Pt—Ba alloys. All the Pd and Pt5Ba grains contain high densities of randomly arranged dislocations, and Pt5Ba grains  contain internal  stresses. Recommendations have been given concerning the improvement of the current Pd—Ba and Pt—Ba cathode alloy tape  technology.

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