Combinatorial synthesis of oxide powders
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Combinatorial libraries of the mixed oxide system Cu1−xCexO3 (0 艋 x 艋 1) have been generated using a modified Pechini powder synthesis process in conjunction with inkjet deposition. Mixed oxide crystalline powders were formed at temperatures below 500 °C. These powders have particle sizes in the range of 20.0 to 85.5 nm, and the powder surface area increases with cerium content. In addition, each of the mixed oxides (0 < x < 1) displayed catalytic activity in the CO oxidation reaction at temperatures between 150 and 350 °C. This novel protocol has also been used to generate a library of oxide powders of the perovskite-like La1−xSrxCoO3−␦ system. The La–Sr–Co–O system from this protocol exhibits lower average surface areas than the Cu–Ce–O system (approximately 11.2 m2/g) due to higher decomposition temperatures but still acts as an active catalyst for the CO oxidation reaction. I. INTRODUCTION
After its successful application to improved drug discovery in the biomedical arena, combinatorial synthesis has become an area of active research in inorganic chemistry and advanced materials. Because of the rapid systematic production of novel compounds it is an appealing technique to generate libraries of compounds for discovery of advanced materials such as phosphors,1,2 dielectrics,3 heterogeneous catalysts,4 and magnetoresistive materials.5 In 1995, Xiang and Schultz first applied the combinatorial method to the study of advanced materials and produced previously known superconducting oxide compounds.6 The combinatorial library in this first study was generated by thin film deposition through a series of binary masks. The thickness of each layer and rearrangement of the masks allowed the systematic deposition of compounds. Since then, thin film deposition has become the primary method for the production of combinatorial libraries of advanced materials on a microscale. Other advanced materials, such as phosphors and heterogeneous catalysts, can benefit from solution-phase syntheses. Applying a scanning multihead inkjet delivery system to the deposition of libraries, Xiang and Schultz developed a solution-phase protocol for the production of combinatorial libraries of phosphor powders.1 Heterogeneous catalyst libraries have since been generated by various other techniques including pellet impregnation,4 “split and pool” solid-phase synthesis,7 sol-gel synthesis,8 hydrothermal synthesis9 and inkjet deposition on graphite paper.10 Infrared4,7 and fluorescence10 imaging are among techniques that have been used to determine the relative activity of the members of the catalyst or phosphor libraries and several new useful compounds have come from these studies. This paper J. Mater. Res., Vol. 16, No. 4, Apr 2001
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describes development of a process for generating combinatorial libraries of oxide powders using a modified Pechini11 method. The modified Pechini or liquid-mix (LM) synthesis route, during which metal salts are chelated with citric acid and undergo polyesterific
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