The swelling and exfoliation behaviors of layered potassium ruthenate and the resultant unilamellar crystallites of RuO2.10.2− with nanosheet morphology were studied. The reaction of layered H0.2RuO2.1·0.9H2O with tetrabutylammonium hydroxide (TBA+OH−) was found to be extremely sensitive to the interlayer water content. The use of highly hydrous layered protonic ruthenate was essential for obtaining direct exfoliation. The swelling behavior was also affected by the ratio of TBA+ to ion-exchangeable H+ in the layered compound. At low ratios of TBA+/H+≤1, the layered precursor scarcely exfoliated and mostly deposited as an intercalation compound. In the intermediate TBA+/H+ range, an auburn colloidal suspension containing exfoliated nanosheets was formed, while much larger ratios were less favorable for the exfoliation.

Three novel lanthanum benzenedicarboxylates La2(BDC)3(H2O)4 (1), La4(BDC)3(OH)6 (2) and La3(BDC)2(OH)5 (3) (BDC = 1,4-benzenedicarboxylate) were synthesized by hydrothermal reactions and their structures determined from single crystal X-ray diffraction. All three compounds are 3D framework structures consisting of layers of LaOn polyhedra cross-linked by BDC ligands along the layer stacking direction. In 1 the layers contain separated [LaO6(H2O)2] polyhedra that are bridged by the carboxylate groups of the BDC anions. Compounds 2 and 3 both have highly condensed lanthanum oxide-hydroxide polyhedra. In 2 the layers are wavy and consist of [LaO5(OH)4] and [LaO4(OH)5] polyhedra that share common corners, edges, and faces. In 3, the layers are similar but comprise [LaO3(OH)5] and [LaO4(OH)5] polyhedra.

The crystal growth of lanthanum hexaboride (LaB6) thin films was examined by applying the laser molecular beam epitaxy (laser MBE) process. C-axis (100) highly-oriented LaB6 thin films could be fabricated on ultrasmooth sapphire (α-Al2O3 single crystal) (0001) substrates with atomic steps of 0.2 nm in height and atomically flat terraces. The obtained film exhibited a smooth surface with root mean square roughness of 0.15 nm. The lattice parameter of the LaB6 thin film was close to the bulk value reported previously. In the case of deposition on commercial mirror-polished sapphire substrates, the grown film was amorphous. The resistivity of the prepared crystalline LaB6 thin films was as low as 2.2 × 10−4 Ω cm and almost constant in the temperature range of 10–300 K.

Topochemical reaction strategies based on two-step intercalation methods are studied. Reactions involving reductive followed by oxidative intercalation are quite effective in making new compounds; the synthesis and characterization of (A2Cl)LaNb2O7 (A = Rb, Cs) are presented. An alternative synthetic route, oxidative followed by reductive intercalation, is also discussed.

We present in here the study by means of electron energy loss spectroscopy (EELS) of several rutile based oxides, having in common the presence of octahedrally oxygen coordinated chromium, [Cr-O6], in three different formal oxidation states: Cr4+ in CrO2, a regular rutile; Cr3+ in CrOOH, a H bonded orthorrombic distorted rutile and in CrTaO4, a metal disordered rutile and Cr2+ in CrTa2O6 an ordered trirutile structure. A linear relationship is observed between the formal oxidation state of chromium in all these rutile oxides and the separation between the Cr-L2,3 and O-K energy loss peaks.

The physical properties of the layered iron superconductors and related phases are discussed starting from first principles calculations. The electronic structure is described as that of metallic Fe2+ square lattice sheets with substantial direct Fe-Fe hopping and interactions with the neighboring anionic pnictogens or chalcogens. The materials have a semi-metallic band structure, and in particular the Fermi surface consists of small cylindrical electron sections centered at the zone corner, and compensating hole sections at the zone boundary. The density of states N(EF) is high placing the materials near itinerant magnetism in general, and furthermore the small Fermi surface sections are well nested leading to a tendency towards a spin density wave. Comparison of experimental and density functional results imply the presence of exceptionally strong spin fluctuations in these materials. Superconductivity is discussed within this context.

An unexpectedly high antiferromagnetic transition temperature (TN = 130 K) has been observed in the double perovskite Ba2154SmMoO6 as a result of a strong interplay between spin, orbital and lattice degrees of freedom. A variable temperature neutron diffraction study of Ba2154SmMoO6 demonstrates that the orbital order below TN is as a result of a Jahn-Teller distortion of the MoO6 octahedra.

A novel ceramic synthesis technique, flame spray pyrolysis (FSP) was investigated for the production of nanophosphor particles. Among the various types of synthesis technique for phosphors, FSP is a powerful method which is capable of producing particles with good crystallinity and high luminescence efficiency. Red light emitting Eu3+ doped Y2O3 nanophosphor was prepared by FSP from nitrate based liquid precursors with high flame temperature. Flame temperature is an important factor to obtain phosphor particles with dense and spherical shape. Different molar percentage of urea was added into the precursor, addition of urea increases the temperature in the flame zone and promotes the formation of nano-size and spherical shaped particles. The importance of urea in the precursor to obtain well dispersed Y2O3:Eu3+ nanophosphor has been studied. The characteristics of nanophosphor such as crystallinity, morphology and photoluminescence in the presence of different moles of urea in nitrate based aqueous solution were investigated. On varying the overall concentration of the precursor, both the optical properties and crystallinity were investigated. XRD spectra showed as-prepared phosphors were obtained directly as cubic phase Y2O3:Eu3+ nanophosphor with high crystallinity and without any post-heat treatments. Luminescence intensity of nanophosphor increased with the amount of urea till 2 M percentages, further increase in urea concentration was found to reduce the PL intensity. We have developed a continuous single-step fabrication method for nanocrystalline Y2O3:Eu3+ nanophosphor without any post-heat treatments procedure.

Methanol has high volumetric energy density and is relatively easy to handle, thus methanol fuel cells have potential applications in automobiles and portable devices. There are two types of methanol fuel cells. The direct type cell oxidizes methanol for power generation while the indirect type first converts methanol to hydrogen and uses it as fuel. Indirect methanol fuel cell has several advantages. It has a higher efficiency compared to the direct type, and does not need hydrogen supply and storage as in the hydrogen fuel cell. However, its size is larger and it is heavier as reforming methanol and removing CO are required. Meanwhile, the catalyst with mechanical support such as ceramic foam or honeycomb accounts for a significant part of its total weight. Thus, its applications are limited, especially in portable devices. As a remedy, we have developed a high surface area/weight ratio, low cost and self-supported catalyst for the indirect methanol fuel cell by using porous biomorphic Cu/CeO2/Al2O3. This ternary system is produced via a chemical method by using cotton as templates. Cu/CeO2 is a catalyst for reforming methanol and for oxidation of CO, and the Al2O3 is to prevent segregation of the Cu and CeO2 fine particles.

To prepare this biomorphic Cu/CeO2/Al2O3, a 0.5 M Boehmite solution was prepared with C9H21O3Al via the Yoldas process. It was then mixed with 0.5 M Cu(NO3)2 and 0.5 M Ce(NO3)3 solutions. The weight percentage ratio of Cu:Ce:Al was 3:2:5 in the mixture. Cotton balls were soaked in the mixture, and they were air dried before sintered in air at temperatures ranged from 400°C to 800°C. The sintered samples were further reduced with diluted hydrogen at 250°C for 2 hours. The final products were characterized via SEM, TEM, XRD, BET, DTA and TGA.

We found that the products maintained the original macroscopic shape and size of the cotton ball and no obvious shrinkage was observed. The SEM images showed that the original internal fibrous networks in the raw cotton was retained in the biomorphic product, however, the fibers became hollow. The XRD result confirmed that the Cu/CeO2/Al2O3 compound was produced when the sintering temperatures between 500°C and 700°C. The sizes of the Cu and CeO2 particles in the products were in nanometer scale. When the sintering temperature was higher than 700°C, CuAl2O4 was produced. When temperature was below 500°C, Cu2O was produced. From the DTA and TGA results, the pyrolysis of soaked cotton occurred between 190°C and 380°C. The sample weight decreased to about 16% of its original at 380°C, and kept almost constant at higher temperatures. The BET area of our products was about 100m2 per gram, which was comparable to those of similar products synthesized by other methods. Our products are self supported and mechanical support was not required. It is expected that the weight of catalysts can be greatly reduced and the energy utilization of the indirect methanol fuel cell can be improved.

Ceria doped-yttrium aluminum garnet (Y3Al5O12:Ce3+, YAG:Ce), which is known as an efficient phosphor, have been widely used in optical display and lighting applications. Improved wet chemical method, sol-gel, has been studied, since conventional solid-state reaction requires a high-temperature and prolonged heating to obtain the pure phase. However, there has been little information, such as on pre-firing temperature, concerning high-quality powder formed by the wet chemical process. In this work, YAG:Ce was synthesized with a salted sol-gel process in which a water solution of inorganic salt with citric acid as additive. Transparent starting sol was pre-fired at 200 ˜ 300°C for 2 hrs in air and final annealing to obtain phase-pure YAG:Ce particles was performed at 1100°C for 2 hrs in argon. The effects of pre-firing temperatures on the crystal structure, morphology and luminescence were investigated. Effects of residual organics in the pre-fired gel on the properties of finally annealed phosphors will be fully discussed on the basis of the results of thermal analysis and chemical structure.

The lithium intercalation chemistry of LiNb6Cl15, a 16 e− Nb-cluster, has been explored in order to obtain new Nb-cluster compounds. As a result, three different phases have been detected. Full de-intercalation of lithium produces Nb6Cl15, a new 15 e− Nb-cluster. The oxidation reaction is reversible since lithium can be intercalated again to produce the parent LiNb6Cl15. On the other hand, intercalation of lithium into LiNb6Cl15 seems to proceed through two single phases with the following stoichiometries: Li1.5Nb6Cl15 and Li3Nb6Cl15. For these two compositions the extra electrons (0.5 and 2 respectively/formula) should enter the eg* molecular orbitals arising from Nb-Nb interactions inside the cluster. The reductions of LiNb6Cl15 leading to these two new electron-rich Nb-cluster are reversible as detected by chronopotentiometry.

The crystal structures of gallium sulfides prepared under solvothermal conditions, using 4-picoline as a solvent, are described. These materials contain [Ga10S16(NC6H7)4]2− clusters, in which the terminal S2− anions have been replaced by covalently bonded 4-picoline molecules. Whilst these phases contain isolated supertetrahedral clusters separated by organic moieties, linkage of such clusters via organic ligands is possible under suitable reaction conditions. These organically-functionalised supertetrahedra could therefore be used to design novel Metal-Organic frameworks (MOFs) in which the normally-encountered metal centers are replaced by supertetrahedral clusters.

We investigated the fabrication of Si nanocrystals, including thin films, by annealing the SiO/C/SiO thin films in an Ar atmosphere. The SiO/C/SiO trilayered thin films were deposited on α-Al2O3 (0001), Si (111), or ITO-coated borosilicate glass substrates at room temperature by pulsed laser deposition using dual sintered SiO and graphite targets. The SiO/C/SiO thin films subjected to heat treatment at 500°C included nanocrystalline Si. Measurements by synchrotron radiation X-ray diffraction indicated the formation of Si nanocrystals having a size of 5–10 nm. Fourier transform infrared spectra showed that Si–O stretching and vibrational peak intensities of the as-deposited thin film decreased remarkably after annealing. The C layer in the SiO/C/SiO trilayered thin films is considered to play a role in enhancing the chemical reaction that produces Si nanocrystals through reduction of SiO during heat treatment. The annealed SiO/C-based thin films, including Si nanocrystals, exhibited photosensitive conduction behavior in current–voltage measurements.

We have prepared five perovskite compounds which have two different A-site cations and examined the ordering of the A-site lattice through powder X-ray diffraction, TEM, HRTEM, HAADF-STEM, STEM-EELS. NaLaTi2O6 and NaLaZr2O6 show no indication of cation ordering by XRD but TEM analysis reveals that the A-site cations are ordered into layers in nanometer domains which have perpendicular orientations of the layers. NaLaMgTeO6 has larger domains which can be detected by XRD. XRD has revealed that both NaLaMgWO6 and KLaMnWO6 have nearly complete long range layered ordering of the A-site cations. TEM microscopy has further shown that a compositional modulation exists in both compounds. NaLaMgWO6 organizes into alternating stripes ˜24Å wide that are compositionally distinct from each other. KLaMnWO6 shows similar behaviour except with a chessboard pattern.

Exploratory synthesis of mixed oxides of rhodium has produced many new rhodates containing both Rh3+ and Rh4+. The structures of all the compounds are based on networks formed from RhO6 octahedra sharing both corners and edges. All compounds exhibit good electrical conductivity, and some also show a high thermopower.

Infinite-layer-structure epitaxial thin films of SrFeO2 and LaNiO2 respectively were prepared by low-temperature reduction with CaH2 from brownmillerite SrFeO2.5 and perovskite LaNiO3 epitaxial thin films grown on single-crystal substrates. The reduction process, removing oxygen ions from the perovskite-structure framework and causing rearrangements of oxygen ions, topotactically transforms the initial compounds to the c-axis oriented infinite-layer-structure epitaxial thin films. Consequently, the oxidation state of transition-metal ions in the film changed in wide ranges.

Prompted by renewed interest in the crystalline oxides-on-semiconductors interface, periodic density functional theory and atomistic simulation techniques are used to examine the formation of a layer of CaO on a BaO substrate. We examine how CaO islands which form at coverages less than 100% adjust to the substrate in which the cation-anion separation is substantially larger than in CaO itself. All Ca-O bond lengths in the island are shorter than that in bulk CaO. Corner O atoms in the islands are associated with particularly short Ca-O bond lengths, and the shape of the islands is dominated by (100) edges. Once formed, islands with intact edges will remain intact. Interactions between islands at larger coverages are also investigated and we see the formation of characteristic elliptical gaps and loops.

Routes to porous materials with nanoscale dimensions have been investigated. In the first example presented, porous manganese oxide has been prepared by leaching Ni metal from a nickel-manganese oxide precursor via reduction. Electron microscopy studies have revealed the presence of Ni nanoparticles on the surface, and also embedded within the porous MnO matrix. Magnetic measurements have shown exchange bias between the ferromagnetic Ni nanoparticles and the antiferromagnetic MnO phase. In the second system studied, porous nanostructures of rutile VO2 and corundum V2O3 have been prepared by reduction of amine-templated V2O5−δ nanoscrolls. The porosity of these materials has been probed by electron microscopy, N2 sorption measurements and thermogravimetric analysis.

At the moment, over 1100 borate crystal structures are listed in the Inorganic Crystal Structure Database ICSD. High-pressure investigations in this field are rare and were mainly performed from a geological point of view. Starting in 1999, systematic high-pressure / high-temperature experiments up to maximum pressures of 16 GPa have been carried out, using the multianvil technique to explore the synthetic possibilities in the field of borates under extreme conditions. This approach led to a variety of interesting new materials, which are unattainable via conventional solid state syntheses. The communication will give a short survey of the most important results in the last years.

The rational design of crystal structures, in particular noncentrosymmetric materials, and how to differentiate polar, polar-chiral, and chiral structures, is an ongoing theme in crystal engineering. In KNaNbOF5, the combination of a second-order Jahn Teller active d0 transition metal oxyfluoride anionic unit and mixed K/Na cation coordination environments are shown to result in a polar structure (space group Pna21). The crystal structure analysis of the Na/K-O/F interactions reveals that the potassium cations form one of the two contacts to the under-bonded oxide ions. These interactions satisfy the expected bond valence sums and Pauling's second crystal rule (PSCR), leading to O/F ordering and acentric packing of the [NbOF5]2− anionic unit.