Molecular Routes to Advanced Materials: Synthesis of NdAlO 3 Ceramic and NdAlO 3 /Al 2 O 3 Composite From Single Source Precursors

Abstract

The success of low-temperature chemical synthesis routes, for obtaining advanced materials, is largely attributed to novel molecular derivatives which can be transformed via solution (Sol-Gel) or gas phase (CVD) reactions into high-purity ceramics or composites at much lower temperatures when compared to the conventional methods. The correct choice of the precursor provides better control over purity, composition, homogenity and microstructure which are the crucial parameters for high performance materials. A major development is the use of single-source precursors where the requirements of the material are inherently present in the starting materials. Some of the salient features of this approach are: (i) chemically controlled decomposition reactions (ii) the possibility of tuning the elemental ratio at a molecular level, (iii) neat transformation processes which produce ultra-pure ceramics or composites. We have used a large variety of metal-alkoxides to obtain metal / metal oxide composites, alloys / metal oxide composites and mixed-metal oxide phases. For example, nano-crystalline lanthanide-aluminates, LnAlO have been homogeneously incorporated in amorphous AlO matrix by using molecular precursors [Ln[Al(OPri)]] (Ln (III) = Pr, Nd, Er) in CVD and Sol-Gel processes. Similarly, size controlled synthesis of nano-spinels, MAlO has been achieved by employing heterometal alkoxides [M[Al(OR)]] (M(II) = Co, Ni, Cu) in a microemulsion mediated sol-gel process.