The first preparation of superionic BaSnF4, BaSnF4(ssr), was carried out in 1975 by direct reaction at high temperature between appropriate amounts of BaF2 and SnF2 under inert conditions in sealed copper tubes. In the present work, BaSnF4(aq2) was synthesized for the first time by the wet method. X-ray powder diffraction and Mössbauer spectroscopy were used to characterize the products, and show that BaSnF4(aq2) and BaSnF4(ssr) are the same material.

We report preparation of highly grain-aligned and densified [Ca2CoO3-δ]0.62CoO2 bulks and a change of thermoelectric performance for their bulks with different oxygen deficiencies (dgrl). The highly c-axis aligned and highly densified samples which showed low electronic resistivities at room temperature, were obtained by combination of magnetic alignment and spark plasma sintering methods. Electronic resistivity p and Seebeck coefficient S along the ab plane were systematically changed with oxygen contents and a power factor was consequently enhanced up to 3.5×10--6 Wcm-1K-2 at 300K for the sample annealed at 500°C in air. Moreover, the magnetic properties also showed a systematic change with oxygen contents.

Nanostructured ferrites possess more advantages than the conventional ferrite materials and have been a research focus recently. In this work, a series of nanostructured Ni0.5Zn0.5Fe2O4 were synthesized by a citrate reaction method followed by calcining at various temperatures with the goal of obtaining pure phase Ni0.5Zn0.5Fe2O4 nanoparticle while keeping the size small. X-ray diffraction, transmission electron microscopy, SQUID magnetometry and Mössbauer spectroscopy (ME) have been employed to characterize the crystal structure, phase homogeneity, particle size, the conditions for reaction completion, and the magnetic properties. The results show that the saturation magnetization Ms at both 10K and 300K increase with increasing calcination temperature Tca, but particle size also increases with Tca. Three factors, the incomplete reaction for ferrite phase formation, the surface effect and superparamagnetic behavior, are found to be responsible for low Ms values at lower Tca. Based on a detailed analysis of nanostructure and magnetic properties in ferrites, the optimal conditions for synthesizing nanostructured Ni0.5Zn0.5Fe2O4 have been established.

The synthesis and structure of triple layered Bi2Ln2Ti3O12 Aurivillius phases, prepared from K2Ln2Ti3O10 Ruddlesden - Popper precursors has been investigated. In structural terms, these materials may be considered as being composed of a regular intergrowth of [Bi2O2]2+ fluorite and [Ln2Ti3O10]2- perovskite-type layers. A significant degree of cation disorder is present in the Bi2Ln2Ti3O12 system, involving the cross substitution of Ln / Bi cations onto the Bi / Ln sites in the fluorite and perovskite-type layers, respectively. Bi / Ln disorder destabilises the presence of the Ln cation in the perovskite-type layer as the size mismatch of the Bi / Ln cations increases. Cation disorder in the Bi2Ln2Ti3O12 system is therefore significantly suppressed as the size of the lanthanide cation is reduced.

Negative thermal expansion behavior has been found in many oxides where oxygen or a cation has a coordination number of two. The MO2, AM2O7, A2M3O12, AMO5, and AO3 families, where A is an octahedral cation, M a tetrahedral cation, and the oxygen coordination is two, have been investigated for their thermal expansion properties. Negative thermal expansion has been found in all families except the AO3 family, where very low thermal expansion was found in the case of TaO2F. Open networks are necessary to allow free transverse thermal motion of oxygen, which is the apparent cause negative thermal expansion in these families. This openness leads to two problems. One is that structure collapse transitions tend to occur as the temperature is lowered. There is little or no thermal expansion below this transition. A solution to this problem is to maintain sufficient ionic character in the bonds holding the network together. The other problem is that when the networks become sufficiently open, they tend to hydrate. This hydration destroys the negative thermal expansion of the network.

Subsolidus compatibility relations in the ternary system Li2O – Sb2O5 – CuO have been determined. One new copper-rich phase, LiCu4SbO7, W, and one new solid solution series, Li1-xSb1-xCu3xO3, over the composition range 0 < × ≤ 0.077 have been prepared. Eight triangles of compatibility were determined at (approximately) 1000 °C.

K2NiF4-type iron(III) oxides show a very common form of magnetic ordering, XY antiferromagnetic ordering within the layers combined with layer stacking based on alignment of spins in alternate layers. The Ising antiferromagnet Ca2MnO4 has been reported to have a doubled c-axis (ca 24Å) in the magnetic structure and we have found a similar stacking in the XY antiferromagnet Sr2FeO3F. We show here that this unusual c-axis doubling is related to the exposure of the material to air and suggest that in both Sr2FeO3F and Ca2MnO4 it may be related to the occupation of interstitial sites.

TTB-type NaNbWO6 has been used to perform sodium-proton exchange reactions by using nitric acid as an exchanging agent. The characterisation of the exchange reaction products, performed by means of chemical analysis, X-ray diffraction and thermogravimetric analysis, indicate that the exchange reaction takes place topotactically. The following formula is proposed for the obtained phase of variable composition: Na1-xHxNbWO6 (0<x<0.46).

Substituted barium ferrites powders with Ti4+-M2+ (M = Co, Zn, Sn) cationic mixtures were prepared by a sol-gel route. The materials were heat-treated in the range 925–1000 °C and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The results showed that the effect of the substitution, x was to lower the coercivity (Hc), owing to the decrease of the magnetocrystalline anisotropy of the magnetoplumbite structure of the BaM. In this regard Sn-Ti substitutions tended to decrease Hc more rapidly than Zn-Ti and Ti-Co substitutions, in that order. Regarding the saturation magnetization (Ms), Zn-Ti mixtures showed slightly better Ms than Ti-Co substitutions; however, the Sn-Ti showed a more marked decrease as x increased. As revealed by SEM, the effect of the heat-treatment temperature was to increase the volume of multi-domain particles, following a Hc decrease due to grain coarsening. Contrarily, as a result of the improved crystallinity of the samples, as observed from the XRD peaks, Ms enhancement was recorded. Crystallite sizes decreased below 100 nm as x increased, although it was also dependent on the cationic mixture. In this respect Sn-Ti substitutions needed higher treatment temperatures to yield materials with adequate crystallinity and phase constitution.

This paper is a survey of recent author's results obtained by the authors. It shows that many oxides can be obtained as thin epitaxial films in spite of their thermodynamic instability in bulk state at the film deposition conditions. This new synthetic approach, named epitaxial stabilization, is based on free energy gain due to structural coherence at the film/substrate interface. The epitaxial stabilization can be effectively used to enlarge the spectrum of new functional materials.

A family of microporous and open-framework microporous transition metal silicates have been prepared by hydrothermal synthesis at T ≤ 240 °C. The structures of the compound are based on a common principle in which anionic silicate components (layers, chains, or cluster anions) are connected by isolated transition metal polyhedra by sharing four corners in a square arrangement. Known examples of this class of compounds are reviewed and some recent progress on extending the syntheses to include organic templates are discussed.

Sr2Nb2O7 and Sr2Ta2O7 have a (110) layered perovskite structure and are efficient photolysis catalysts. Aqueous silver and lead cations were photochemically reduced and oxidized, respectively, on the surfaces of Sr2Nb2O7 and Sr2Ta2O7 crystals with a wide range of orientations. Atomic force microscopy has been used to observe the distribution of photochemically reduced and oxidized products and determine the orientation dependence of the reactivity. On surfaces with the same orientation, reaction products frequently had a non-uniform distribution. The reactivity of both compounds proved to be only weakly anisotropic, with the highest relative reactivity for both oxidation and reduction occurring for surfaces oriented between (010), (110), and (011). These low index orientations have structures similar to the ideal {110} and {100} planes in the perovskite structure, respectively. The relationship of the perovskite structure to the reactivity is discussed.