II. Structure of Perovskites 1982 A. Crystal Structure 1982 B. Nonstoichiometry in Perovskites 1983 1. Oxygen Nonstoichiometry 1983 2. Cation Nonstoichiometry 1984 C. Physical Properties 1985 D. Adsorption Properties 1986 1. CO and NO Adsorption 1986 2. Oxygen Adsorption 1987 E. Specific Surface and Porosity 1987 F. Thermal Stability in a Reducing Atmosphere 1989 III. Acid−Base and Redox Properties 1990 A. Acidity and Basicity 1990 B. Redox Processes 1991 1. Kinetics and Mechanisms 1992 2. Reduction−Oxidation Cycles 1993 C. Ion Mobility 1993 1. Oxygen Transport 1993 2. Cation Transport 1994 IV. Heterogeneous Catalysis 1995 A. Oxidation Reactions 1995 1. CO Oxidation 1995 2. Oxidation of Hydrocarbons 1996 B. Pollution Abatement 2001 1. NOx Decomposition 2001 2. Exhaust Treatment 2002 3. Stability 2004 C. Hydrogenation and Hydrogenolysis Reactions 2004 1. Hydrogenation of Carbon Oxides 2004 2. Hydrogenation and Hydrogenolysis Reactions 2006

Chemical structures and performance of perovskite oxides.

Catalytic removal of NO

Oxidation into CO2 is a major solution to CO abatement in air depollution treatments. The development of catalytic converters led to an extraordinary high number of publications on metal catalysts during the last fifty years. Due to the increasing price of noble metals and to remarkable progresses in oxide syntheses, catalytic oxidation of carbon monoxide over oxide catalysts has recently gained in interest, even if some oxides are known to present remarkable activity since the beginning of the 20th century. In this Review, the kinetics and mechanism of CO oxidation on single and mixed oxides are examined, alongside the catalyst structures

Catalytic Oxidation of Carbon Monoxide over Transition Metal Oxides

Perovskites as substitutes of noble metals for heterogeneous catalysis: dream or reality.

Structural and magnetic properties, methods of synthesis, and applications of seven iron(III) oxide polymorphs, including rare beta, epsilon, amorphous, and high-pressure forms, are reviewed. Thermal transformations resulting in the formation of iron oxides are classified according to different parameters, and their mechanisms are discussed. 57Fe Mossbauer spectroscopy is presented as a powerful tool for the identification, distinction, and characterization of individual polymorphs. The advantages of Mossbauer spectroscopy are demonstrated with two examples related to the study of the thermally induced solid-state reactions of Fe2(SO4)3.

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications†

Semiconducting barium titanate has been prepared both by coprecipitating the lanthanum in the preparation of barium titanyl oxalate and by precipitation of lanthanum hydroxide in a slurry of the titanate. Partial substitution of strontium or lead for barium and zirconium for titanium has also been achieved using this oxalate process. The electrical conductivity of these materials was measured and is discussed. The effect of excess titanium on the electrical properties was also determined and an excess of 1 to 2 mole % was found to raise the positive temperature coefficient under the firing conditions employed.

Preparation of Semiconducting Titanates by Chemical Methods

Lanthanum-doped Ba0.6Sr0.44TiO (OH)2C2O4.4H2O was prepared by precipitation from a pH-controlled oxalic acid solution for conversion to the titanate. TGA and DTA support the proposed formula of a hydrated, mixed hydroxyoxalate. Density and resistivity measurements of the titanates are correlated as a function of lanthanum content.

Effect of pH on the Chemical Preparation of Barium‐Strontium Titanate

Thermal analysis has been performed on BaTiO(C2O4)2.4H2O, Ba0.6Sr0.4TiO(C2O4)2.4H2O, Sr(TiO(C2O4)2.4H2O, Ba0.9Pb0.1TiO(C2O4)2.4H2O, and BaTi0.9Zr0.1O(C2O4)2.4H2O. It was observed that the strontium compound decomposes differently than the others. Previous investigators have proposed conflicting mechanisms for the pyrolysis of the barium salt and these results are discussed in comparison with this work. The electrical resistivity and temperature coefficient of fired lanthanum-doped materials were found to vary with the calcination temperature. Maximum conductivity was observed in samples calcined at 900°C whereas maximum positive temperature coefficient was observed for materials calcined at 1050°C. Particle sizes of the calcined material were compared with grain sizes in the fired pieces and correlated with the electrical properties. A cursory examination was made on the effects of fabrication pressure, 1.25 to 15 tsi, on the electrical conductivity. Both the conductivity and positive temperature coefficient were found to increase with decreasing fabrication pressure.

F. Schrey

Papers

Preparation of Semiconducting Titanates by Chemical Methods

Effect of pH on the Chemical Preparation of Barium‐Strontium Titanate

Thermal Decomposition of Some Substituted Barium Titanyl Oxalates and Its Effect on the Semiconducting Properties of the Doped Materials

Studies of some supported perovskite oxidation catalysts

Preparation of high surface area substituted LaMnO/sub 3/ catalysts