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Metal flux synthesis in a low-melting eutectic mixture of lanthanum and nickel has produced a family of complex intermetallic carbide phases. La(21)Fe(8)M(7)C(12) (M = Sn, Bi, Sb, Te, Ge) has a new cubic structure featuring tetrahedra of iron atoms capped with carbon on each edge. These tetrahedra are surrounded by a La/M framework and are therefore isolated from each other. The antiferromagnetic coupling of the iron atoms is frustrated by their ideal tetrahedral arrangement; this is evidenced by magnetic susceptibility measurements on the La(21)Fe(8)Sn(7)C(12) analogue. Deviations from Curie-Weiss behavior begin at 100 K; variation in field-cooled vs zero-field-cooled behavior is seen at 5 K indicative of magnetic ordering. AC susceptibility data indicate that the temperature of this transition is frequency-dependent, behavior characteristic of spin glass systems.

The combination of early rare earth metals (La- to Gd and Yb), gold, and silicon in molten aluminum results in the formation of intermetallic compounds with four related structures, forming a new homologous series: RE[AuAl2]nAl2(AuxSi(1-x))2, with x approximately 0.5 for most of the compound and n = 0, 1, 2, and 3. Because of the highly reducing nature of the Al flux, rare earth oxides instead of metals can also be used in these reactions. These compounds grow as large plate-like crystals and have tetragonal structure types that can be viewed as intergrowths of the BaAl4 structure and antifluorite-type AuAl2 layers. REAuAl2Si materials form with the BaAl4 structure type in space group I4/mmm (cell parameters for the La analogue are a = 4.322(2) A, c = 10.750(4) A, and Z = 2). REAu2Al4Si forms in a new ordered superstructure of the KCu4S3 structure type, with space group P4/nmm and cell parameters of the La analogue of a = 6.0973(6) A, c = 8.206(1) A, and Z = 2. REAu3Al6Si forms in a new I4/mmm symmetry structure type with cell parameters of a = 4.2733(7) A, c = 22.582(5) A, and Z = 2 for RE = Eu. The end member of the series, REAu4Al8Si, forms in space group P4/mmm with cell parameters for the Yb analogue of a = 4.2294(4) A, c = 14.422(2) A, and Z = 1. New intergrowth structures containing two different kinds of AuAl2 layers were also observed. The magnetic behavior of all these compounds is derived from the RE ions. Comparison of the susceptibility data for the europium compounds indicates a switch from 3-D magnetic interactions to 2-D interactions as the size of the AuAl2 layer increases. The Yb ions in YbAu(2.91)Al(6)Si(1.09) and YbAu(3.86)Al(8)Si(1.14) are divalent at high temperatures.

Eighteen new intermetallic compounds RMn2TrxZn20� x (2oxo7; R ¼ rare-earth metal; Tr ¼ Al, In) were synthesized using low- melting mixtures of (Tr/Zn) as a solvent. Structural refinement using single-crystal X-ray diffraction data shows that the compounds are substituted variants of the cubic CeCr2Al20-type structure (Fd-3m, Z ¼ 8; unit cell parameters vary from a ¼ 14.1152(3)Afor YbMn2Al5.3Zn14.7 to a ¼ 14.8125(4)Afor SmMn2In5.9Zn14.1). The Zn and Tr elements show site preferences in the indium compounds, but not in the aluminum analogs. The substitution of trielide element for zinc modifies the valence electron count of the compounds to allow for the incorporation of Mn into the structure. Magnetic susceptibility data show no evidence of magnetic ordering down to 3 K.

New intermetallic phases were synthesized by reacting oxidic perovskites and gold metal in aluminum flux. The combination of MTiO3 (M = Ca, Sr, Ba) and Au metal in excess molten aluminum produces quaternary compounds M3Au6+xAl26Ti with a stuffed BaHg11 structure type. An analogue with M = Yb was also synthesized; it shows mixed valent behavior.

REAu4Al8Si (RE = Ce-Gd, and Yb) is the end member of a new series of intermetallic structures grown from aluminium flux; this new structure contains thick AuAl2 slabs and the ytterbium analog exhibits mixed-valent behavior.

A series of antimony-doped Ba(8)Ga(16)Ge(30) clathrates was grown as large crystals from gallium flux. These compounds form in the cubic space group Pm(-)3n, with the unit cell parameter varying from 10.784(5) to 10.9008(6) A as the amount of GaSb substituting for germanium atoms in the framework is increased. It was found that more antimony than extra gallium was incorporated into the material and that a specific site (the 24k Wyckoff site) was favored by this element. (71)Ga NMR was carried out to determine the siting of gallium; it fills the 6c site preferentially.

A silicon framework clathrate type-II compound was synthesized with rubidium and sodium atoms in cages. A single crystal of this material was characterized by both conventional and synchrotron x-ray diffraction; the structure belongs to the cubic space group $Fd\ensuremath{-}3m,$ with a cell edge of 14.738(1) \AA{}. The alkali metals are ordered in the structure, with the small cages containing sodium, and the large cages containing rubidium. Variable temperature magic-angle-spinning NMR of all three nuclei show large Knight shifts with a strong temperature dependence, unlike conventional metals. The low conductivity (200 S/cm) and high paramagnetic susceptibility $(5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\mathrm{e}\mathrm{m}\mathrm{u}/\mathrm{g})$ indicate that as the temperature is lowered, the electrons become more localized on the alkali atoms, resulting in properties consistent with a correlated narrow band metal system.

Germanium clathrates have recently received attention as potential highly efficient thermoelectric materials based on the phonon glass electron crystal (PGEC) concept [1-4]. A combined EXAFS and XANES study has been performed in order to investigate the local structure and the degree of charge transfer between the guest atoms and the framework atoms. Analysis of the Sr, Ga, and Ge K-edge XANES spectra of a Sr8Ga16Ge30 clathrate reveals that the atoms are close to neutrally charged and that the degree of charge transfer is low in agreement with recent theoretical predictions and charge density distribution measurements [3,5].

Use of the Zintl phase KSn as a source of potassium dopant in tin flux syntheses of Ba(1-x)K(x)Fe(2)As(2) allows for incorporation of large amounts of potassium with much less attack on reaction vessels compared to the use of elemental potassium as a reactant; it also enables further study of tin incorporation into the products.

Traditional aqueous methods of cation exchange in zeolites present complications for the exchange of catalytically important transition metal and rare earth ions. Ethylene oxide-based oligomers (polyethylene glycol, polyethylene glycol methyl ether, diglyme, tetraglyme, and polypropylene glycol) are being investigated as alternative media for zeolite ion exchange. Reactions using lithium as the exchanging species indicate that these solvents can be used successfully for ion exchange in hydrosodalite and dehydrated sodalite zeolites, enabling these reactions to be carried out in the absence of water. The oligomer solutions allow for the exchange of 88% to 99% of sodium ions for lithium ions after 3–5 exchange cycles at 100 °C in both hydrosodalite and dehydrated sodalite as determined by unit cell parameters and elemental analysis.

Maximum entropy method (MEM) charge density analysis has been carried out on synchrotron X-ray powder diffraction data of a series of anhydrous sodalites, M6(AlSiO4)6, M = Na, Ag, Tl. Analysis of t...