PHASE FORMATION IN Li2MoO4-Rb2MoO4-MMoO4 (M = Ca, Sr, Ba, Pb) SYSTEMS AND THE CRYSTAL STRUCTURE OF О±-Rb2Pb(MoO4)2
I. A. Gudkova, Z. A. Solodovnikova, S. F. Solodovnikov, E. S. Zolotova, N. V. Kuratieva
Keywords: lithium, rubidium, alkaline-earth metals, lead, binary molybdates, phase relations, solid solutions, crystal structure, palmierite
Pages: 1101-1107
Abstract
A subsolidus triangulation of Li2MoO4-Rb2MoO4-MMoO4 (M = Ca, Sr, Pb, Ba) systems is performed. The RbLiMoO4-Rb2M(MoO4)2 (M = Pb, Ba) joins, where 11 mol.% long Rb2M(MoO4)2-based solid solutions are found, are studied in most detail. Ternary molybdates do not form in the systems, which is confirmed by spontaneous flux crystallization. The α-Rb2Pb(MoO4)2 crystals are obtained and their crystal structure is solved (а = 20.9724(15) Å, b = 12.1261(8) Å, с = 16.1171(10) Å, β = 115.728(13)°, С2/m space group, R = 0.0695, Z = 16), which is a monoclinic superstructure of the palmierite type and has the largest cell volume and the most complex structure among lead-containing palmierites. One of the MoO6 tetrahedra is orientationally disordered over two sites; lead atoms are shifted from the centers of their coordination polyhedra to one of their faces and have cn = 6-8; for rubidium cations cn = 10-12.
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