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In the RE-Ru-Al systems, in the region with high content of rare earth elements a number of isostructural compounds RE 10 RuAl 3 (RE = Gd, Tb, Dy, Ho, Er, Tm) were identified. The structures of the obtained compounds belong to ordered variant of anti -Co 2 Al 5 -type with a hexagonal cell, space group P 6 3 / mmc (No. 194), Pearson symbol hP 28 , Z = 2, the cell parameters a = 9.5901(19) Å, c = 9.6504(17) Å (Gd); a = 9.5029(17) Å, c = 9.5746(20) Å (Tb); a = 9.4761(17) Å, c = 9.5544(13) Å (Dy); a = 9.4235(9) Å, c = 9.5132(7) Å (Ho); a = 9.3967(6) Å, c = 9.4761(5) Å (Er); a = 9.3589(12) Å, c = 9.4277(10) Å (Tm). All compounds were synthesized by arc-melting the stoichiometric quantities of elementary components. The structures were determined by X-ray diffraction analysis of a single crystal and refined by the Rietveld method from powder X-ray diffraction patterns. In the structure of the compound Ho 10 RuAl 3 one of the three holmium sites - Ho3 - was mixed with Al, which is reflected in the composition of the intermetallide: compound with Ho shows a small deviation from composition RE 10 RuAl 3 and an adequate formula of the compound is Ho 10‒x RuAl 3+x (x = 0.07). The crystal structure of the compounds can be represented as rows of trigonal prisms with rare earth atoms at the vertices, centered by ruthenium atoms, alternating with a pair of empty octahedra of rare earth atoms along the direction c of the unit cell. Rows of prisms and octahedrons separate distorted icosahedrons RE[Al 6 RE 6 ] with a rare earth atom in the center, connected by common triangular faces. All obtained compounds have a congruent melting pattern. [Display omitted] • Six novel ternary intermetallic compounds RE 10 RuAl 3 (RE = Gd, Tb, Dy, Ho, Er, Tm) were prepared. • Two fundamentally different ways of describing the crystal structure of the obtained compounds were considered. • Compound Ho 10 RuAl 3 is characterized by a mixed occupancy of one of the holmium sites by aluminum and holmium atoms. • Intermetallic compounds RE 10 RuAl 3 (RE = Gd, Tb, Dy, Ho, Er, Tm) melt congruently. [ABSTRACT FROM AUTHOR]

Abstract: Six new transition metal(III) phosphites A I[VIII(HPO3)2], where A=K (1), NH4 (2) and Rb (3) and A I[FeIII(HPO3)2] where A=K (4), NH4 (5) and Rb (6) have been synthesized under hydrothermal conditions and the solid-state structures were solved from single-crystal X-ray diffraction data. These compounds crystallize in the hexagonal system, space group P63 mc (no. 186), with a=5.3294(2)Å and c=12.3130(5)Å for 1, a=5.3330(2)Å and c=12.8760(4)Å for 2, a=5.3459(2)Å and c=12.6850(8)Å for 3, a=5.3256(1)Å and c=12.2362(3)Å for 4, a=5.3229(2)Å and c=12.8562(4)Å for 5, a=5.3393(2)Å and c=12.6913(5)Å for 6, with Z=2 in the six phases. The crystal structures of these compounds are isotypic and exhibit a layered structure stacked along the c-axis with the A + cations located in the interlayer space. The [M III(HPO3)2]− sheets are formed by MO6 octahedra interconnected by HPO3 tetrahedral phosphite oxoanions through sharing vertices. Thermal analysis shows a large range of stability for compounds containing potassium and rubidium cations with decomposition starting around 550K for stable compounds and above 840K for the most stable compounds leading in general to pyrophosphate compounds. Triangular nets of metallic centers are observed within the layers in which antiferromagnetic interactions are evidenced by magnetic susceptibility measurements suggesting magnetic frustration. [Copyright &y& Elsevier]