Perovskites mixed metal oxides

Three-Dimensionally Ordered Macroporous (3DOM) Perovskite Mixed Metal Oxides... 

Perovskite mixed metal oxide ABO3 exhibits many interesting and intriguing properties from both the theoretical and the application point of view described in other chapters in this book. Recently, much attention has been paid to the preparation of 3DOM perovskite mixed metal oxides in order to enhance their performances. At present, most attention has been paid to the enhancement of catalytic activities of perovskite mixed metal oxides [9]. 

Perovskite mixed metal oxides are prepared by solid-state reactions and solution methods. In the solid-state reaction, mixtures of precursors (metal oxides or carbonates) are calcined at near 1000 °C. There has been no report to prepare 3DOM perovskite mixed metal oxides by the solid-state reaction. It is difficult to fill the nanometer-scale voids in the template with solid precursors. 

In order to produce 3DOM perovskite mixed metal oxides, selection of precursor solutions is the most important. The precursor solutions should fulfill the following criteria (1) Reactivity of the metal precursor solution should be mild so that it can infiltrate into the voids. If the metal precursor reacts with a functional group on the surface of the template or moisture in the air before it infiltrates the voids, the voids are not filled by the precursor solution. (2) Sufficient metal should be present in the voids to form a macroporous wall, and the metal concentration should therefore be high (usually more than 1 M). When metal concentration is not high enough, repeated infiltration and solidification process should be done. (3) The metal precursor should be solidified in the voids before the template changes their size. In the case of polymer spheres, the polymer... 

Preparation of 3D0M Perovskite Mixed Metal Oxides 125... 

In the case of Ti-based perovskite mixed metal oxides, precursor solutions of Ti alkoxide such as Ti(OiPr)4 and Ti(OBu)4 mixed with other metal sources are used. The Ti-based alkoxide solution is so mild that the solution infiltrates into the voids, and the solution is so reactive that it solidifies in the voids by heating to less than 90 °C. When metal concentration is not high enough, repeated infiltration and solidification is possible to enhance the amount of metal in the voids. 

Here we summarized methods to produce 3DOM perovskite mixed metal oxides with pore sizes in the submicrometer range. There are many methods to produce 3DOM perovskites with many kinds of metals. The 3DOM structure ensures access of molecules and ions to the surfe.ce of perovskite mixed metal oxides, and many advantages of the 3DOM structure have been reported. It is expected that the introduction of 3DOM structure is one important way to enhance the performance of perovskite mixed oxides. 

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