Lead monoxide exists at room temperature in two forms, namely α-PbO, litharge (red, tetragonal) and β3-PbO massicot (yellow, orthorhombic). The weak bonds along the c axis and the ferroelastic nature of the incommensurate phase prevent the growth of single crystals suitable for high quality diffraction techniques (very small ferroelastic domains and frequent stacking faults in these layered structures). A structural determination of the incommensurate structure was proposed in the superspace group C2mb(0β;0) using the integrated intensities extracted from powder diffraction patterns. More recently an electron microscopy study suggested the existence of systematic extinctions affecting the satellite reflections and it supports the more symmetric space group Cmma(0β0)s. In this paper, high resolution powder diffraction patterns (synchrotron) were refined in the incommensurate phase using the Rietveld method. Various superspace groups and forms for the modulated displacements were tested. The consequences of this structural model on the electronic structure are analysed using also ab-initio calculations.

The orthorhombic clathrate compound Eu4Ga8Ge16 orders antiferromagnetically at about 8 K. The magnetic structure is established by neutron powder diffraction while the thermal expansion and atomic displacement parameters are studied by synchrotron powder diffraction. The Eu spins align along the a-axis and achieve a zero-temperature magnetic moment equivalent to that of the free Eu2+ ion. The thermal expansion is largest along the a-axis while the expansion along c has almost the same magnitude as that along b. The Eu displacement parameters display significant residual values at 0 K, largest in the c direction.

We report preparation and thermoelectric properties of c-axis aligned and densified Ca3Co4O9 and [Ca2(Co0.65Cu0.35)2O4]0.624CoO2 polycrystals. The c-axis alignment and densification were accomplished by magnetic alignment and spark plasma sintering methods, respectively. The obtained samples showed high degrees of c-axis orientation and relative densities, which were close to those of single crystals, resulting in the highest values of power factors in Ca3Co4O9 and [Ca2(Co0.65Cu0.35)2O4]0.624CoO2 polycrystals.

Variable-emittance radiators based on the metal-insulator transition of (La,Sr)MnO3 have been developed. The emittance property of the material was evaluated from infrared reflectance spectra; that is, (La,Sr)MnO3 shows low emittance at low temperature but high emittance at high temperature. Moreover, the emittance property significantly changes at the metal-insulator transition temperature, where the material changes from a highly reflective (i.e., low emissivity) metal to a less reflective (i.e., high emissivity) insulator. The (La,Sr)MnO3 thin-films fitted on a spacecraft surface can, therefore, be used to automatically control the emmisive heat transfer from the spacecraft without the need for electrical power. The developed (La,Sr)MnO3 thin-film radiator also greatly reduces the weight and production cost of the thermal control devices.

All the known phases in the PbF2/SnF2 system have structures derived from the fluorite-type β-PbF2, and are either disordered, and therefore cubic, or ordered with lattice distortion and superstructures. In addition, they are the highest performance fluoride-ion conductors, with PbSnF4 being the very best. In this work, a new phase, Pb2SnF6 has been prepared and characterized. Contrary to the other lead(II) tin(II) fluorides known up to date, the structure of Pb2SnF6 is a superstructure of a-PbF2, instead of β-PbF2, with a large (4 × 4) bidimensional supercell. Pb2SnF6 is prepared by the reaction of a-PbF2 with an aqueous solution of SnF2.

High quality Bi2O3 based Er-doped films for planar waveguide amplifier have been deposited by sputtering from sintered targets. It was found that both the amount of residual water and the Er concentration in films mainly affected a lifetime of the fluorescence at 1530nm. By optimizing these parameters, we have obtained films with a lifetime over 3msec, as the same as that of bulk glass prepared by the melting method.

Bi(III)-containing perovskites Bi1/2Ag1/2TiO3 and Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni) were synthesized under oxygen pressure as high as approximately 1 MPa and under a pressure as high as 6 GPa, and the lattice distortions were investigated. It was found that ferroelectric Bi1/2Ag1/2TiO3 may be rhombohedrally distorted. In constrast, Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni), the structure of which is different from GdFeO3-type compound, is monoclinically distorted. The ratio of lattice parameters of the monoclinic perovskite-subcell for Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni), am/bm is larger than that of GdFeO3-type perovskites, though the tolerance factor is close. In addition, it was found that Bi(Ni1/2Ti1/2)O3 undergoes a first-order phase transition from a GdFeO3-type phase(high-temperature phase) at around 490 K. These results indicate that the Bi3+ character in Bi(III)-containing perovskites strongly influences the structure distortion.

Despite its importance as a cathode material in primary alkaline batteries, the structure of γ-MnO2 is still not well determined. Different authors have suggested that a number of different polymorphs, as well as highly disordered phases, may be present in γ-MnO2. The origin of this structural complexity remains largely unexplained. In this paper we use first principles methods to explore the energetics of the MnO2 system. We find a number of low-energy polymorphs with similar energies, suggesting that relatively small changes in the energetics might influence the stable phases. Using nonzero-temperature models we demonstrate that thermal disorder is not the cause of structural disorder in these materials. However, we then show that point (Ruetschi) defects, even in surprisingly low concentrations, have a dramatic effect on the phase stability. We propose that Ruetschi defects may be the key to some of the structural complexity in γ-MnO2, and that any realistic structural study must take them into account.

Nanostructured cobalt particles with and without a ceramic coating have been synthesized using a wet chemical method. The structure and magnetic properties of synthesized powder were characterized using x-ray diffraction (“XRD”), high-resolution transmission electron microscopy (“HRTEM”), and a Quantum Design (SQUID) magnetometer. The cobalt nanoparticles are of either face-centered cubic (“fcc”) and/or hexagonally close-packed (“hcp”) crystalline structures. The average grain size is ∼14 nm for cobalt (either fcc or hcp) with an amorphous silica coating, and the average grain size is ∼9 nm for hcp cobalt and 26 nm for fcc cobalt without a silica coating. The effect of annealing temperature on grain size and magnetic properties are addressed.

Open framework materials are of great interest due to the applications in the fields of adsorption, ion exchange, molecular sieving and catalysis. Metal phosphates are very important open framework materials due to the rich crystallography. Several new iron phosphate materials have been synthesized and characterized in our lab. Two new iron (III) phosphates, FePO4, have been synthesized from careful dehydration of hydrothermally prepared monoclinic and orthorhombic hydrated phosphates FePO4·2H2O. Reversible insertion and extraction of lithium into new iron phosphate hydroxide materials with 3-d rod-packing framework shows it to be an excellent intercalation material. Several other transition metals are also incorporated successfully into these compounds without changing the structure. With ethylenediamine as template, 1-D chain, 2-D layered and 3-D network iron phosphate materials were synthesized. The structure, electrochemical and magnetic properties of these compounds were studied. Meanwhile, two new zinc phosphates with methylammonium templates were also synthesized. There are infinite Zn-O-Zn chains in one of the compounds, while closed 4-member circuits made up from Zn-O-Zn linkage present in the other.

We investigated synthesis, structure, composition as well as electric and magnetic properties of copper tantalum oxide single crystals and powder samples. It was possible to flux-grow single crystals of undoped Cu2Ta4O12. To modify the copper content in this structure, tetravalent and hexavalent ions like titanium and tungsten have been incorporated. Rietveld refinement data as well as magnetic and dielectric properties are presented.

Bismuth layer structured ferroelectrics show interesting physical property variations as a function of external parameters viz., temperature, frequency and magnetic field. In some of these materials, when a magnetic ion is incorporated in the lattice, they show simultaneous ferroelectricity and magnetism, thus exhibiting magnetoelectric output under the influence of an external magnetic field. This paper reports the synthesis and characterization of Bi6Mn2Ti3O18(BMT) which is isomorphous with Bi6Fe2Ti3O18(BFT). The material was prepared both by solid state and microwave sintering routes. The characterization includes X-ray, SEM, conductivity, dielectric constant and pyroelectric coefficient. The results are compared with Fe containing analogue.

Members of the Ruddlesden-Popper system, La2Ni(1-x)CoxO4+δ (0.00 ≤ × ≤ 1.00), were synthesized and studied for their potential use as cathodes for solid-oxide fuel cells. An unusual structural trend has been noted across the series, which appears to correlate with the oxygen-hyperstoichiometry observed. Details of the structural variance by x-ray and neutron diffraction, as well as selected physical properties for this system will be presented.

Results of SDFT calculations were used to construct and check features of a generally applicable qualitative approach to understanding magnetic coupling in rare-earth-rich compounds. Using fragments based on structures of metal-rich lanthanide compounds, we have investigated molecular and low-dimensional extended structures, including Gd3I6(OPH3)12, Gd6I12Co(OPH3)6, and Gd2Cl3. Open-d-shell clusters facilitate strong ferromagnetic coupling whereas in the closed-d-shell systems prefer antiferromagnetic coupling. The f-d exchange interaction, mediated by spin polarization of both filled and partially-filled metal-metal bonding orbitals, was described for the model system Gd3I6(OPH3)12n+ using basic perturbation methods. This method has been successful for predicting the magnetic ground state for models of Gd[Gd6I12Fe] and Gd2Cl3.

Cryptomelane-type manganic acids (CMAs) synthesized by a soft-chemical redox process of KMnO4 with MnSO4 in H2SO4 and α-MnO2s by a decomposition-oxidation process of (CH3)3COK and MnCO3 at 530°C were studied by using the vibrational spectroscopy and 7Li- and 2H-MAS NMR. The infrared absorption bands of the α-MnO2s at 706cm-1 were not changed irrespective of the sort of alkali cations and their uptake amount, while large shifts of this band were observed on the CMA exchanged by alkali cations. Hence, cation-exchange sites of these solids will occupy crystallographically different positions. 7Li-MAS NMR spectra of these manganic acids showed different two chemical shifts depending on their synthetic routes. These findings suggest that different ion-exchange sites are formed at a local level in the 2×2 type tunnel, strongly depending on their synthetic conditions. These are crucial for the control of the cation affinity. These details at a molecular level cannot be obtained by using the conventional XRD analyses.

Three cross-linking reagents (PVA, glycerol and glucose) have successfully been used to synthesize non-doped and metal-doped nanosized cryptomelane materials via a solid-state preparation method. The 2×2 tunnel structure of cryptomelane was formed at 500 °C. FT-IR data show that no cross-linking reagent residues were found in the products after the reactions were complete at 800 °C. The metal dopants used were Fe, Ag, Co, Cu, Ni, and Zn. XRD data show that Fe and Co cations can be doped into the materials without the formation of additional phases. The tunnel structures of the nanosized materials exhibit long-range along the b axis, as indicated by transmission electron microscopy data. High-resolution scanning electron microscopy studies show that morphologies of the products are nanorods or nanofibers, depending on the cross-linking reagents used in the preparation. Thermogravimetric analyses indicate that these nanomaterials are thermally stable to 700 °C.

Aseries of well crystallized Ba1-xSrxMoO4 (0≤×≤1) films were prepared on molybdenum substrates in electrolytes embodied Ba2+ and Sr2+ions by electrochemical deposition at room temperature. The composition x is controlled through the starting concentrations of Ba2+ and Sr2+ ions. The measurements of XRD, SEM and XPS for these materials were carried out. The XRD analyses show that the films are good crystalline with single tetragonal structure of scheelite-type, and the a and c axes of the unit cell parameters of the films decrease with the increasing of Sr2+ concentration in the starting electrolytes; the XPS analyses reveal that the composition of the Ba1-xSrxMoO4 films is in agreement with stoichiometry, and the SEM photographs show that the films are condensed deposited.

The effect of doping europium on the structure of strontium aluminate (SrAl2O4:Eu) synthesized by spray pyrolysis was studied. Results revealed that all of the as-sprayed samples were a mixture structure of monoclinic and hexagonal phases. However, the structural behaviors of the SrAl2O4:Eu post-calcinated at 1300°C in reducing ambient for 2hrs strongly depended on the europium concentrations. As increase of the europium concentrations, a characteristic of hexagonal phase could be observed from the post-annealed samples. Up to 12 percent of strontium were replaced by the europium, the structure of the post-annealed sample achieved a pure hexagonal phase. The mechanism of the phase dependence of the SrAl2O4:Eu on europium concentration was discussed.

Three-layer Aurivillius ceramics Bi2SrCaNb2TiO12, Bi2Sr1.5Ca.5Nb2TiO12, Bi2Sr2Nb2TiO12, Bi2Sr1.5Ba.5Nb2TiO12, Bi2SrBaNb2TiO12 were formed via solid-state synthesis and their structures characterized by Rietveld analysis of powder x-ray diffraction data. Site mixing was observed for all species with the largest amount of mixing occurring in Bi2SrBaNb2TiO12. Bond valence sum calculations (BVS) showed that the A-site BVS increased from underbonded in the Bi2SrCaNb2TiO12 composition to overbonded in Bi2SrBaNb2TiO12. The A-site BVS increased linearly with lattice parameter and average A-site cation radius. Bi-site position relaxation was observed as the average size of the alkaline earth cation on the Bi-site increased. Site mixing occurs in these compounds in order to relieve interlayer strain between the (Bi2O2)2+ layer and the perovskite blocks, between the Nb and Ti-layers of the perovskite blocks, and to reduce the BVS of the perovskite A-site.

We report the synthetic conditions, physical properties and potential applications of late group 14 metal (Sn) 0D, 1D, 2D and 3D extended materials. The structures are primarily neutral chain and anionic layered compounds. The latter are charge-balanced by ammonium cations, as in and BING-7 [Sn(C2O4)F-] [NH4+] and BING-8 [Sn(PO4H)F-] [NH4+]. The neutral layered compound and chain compounds BING-1 [Na4Sn4(C2O4)F6], BING-2 [KSn(C2O4)F] and BING-4 [Sn(C2O4)(C5H5N)] have also been synthesized solvothermally. Thermogravimetric analysis (TGA) under nitrogen and in-situ variable temperature X-ray diffraction show that the materials decompose in the 200°C to 300°C range to more stable phases. Nuclear magnetic resonance (NMR) was used to monitor the ion-exchange properties of some of the materials. The intercalation properties of these materials are still being investigated.