Accession Number : ADA299691

Title :   Nano-Structures via Diffusion Limited Crystallization from Solution Precursors: Synthesis and Properties.

Descriptive Note : Final rept. 15 Apr 94-14 Apr 95,

Corporate Author : CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING

Personal Author(s) : Lange, Fred F.

PDF Url : ADA299691

Report Date : 15 JUN 1995

Pagination or Media Count : 95

Abstract : This program has emphasized two topics: (1) the crystallization of metastable, solid-solution structures, their partitioning into equilibrium structures and compositions, and the role of the metastable phase and its partitioning on forming unique, nanometer microstructures important to the mechanics of structural ceramics and their composites, and (2) the formation of single crystal thin films via spin coating single crystal substrates with solution precursors. Results for the first topic are new, namely, the discovery that diffusion limited crystallization concepts used in rapid solidification directly applies to precursors that crystallize at low temperatures during heating. This discovery is significant because solid-solutions can be greatly extended relative to high temperature synthesis and processing routes where equilibrium conditions are rapidly achieved and solid-solutions can be severely limited. Extension of solid-solution fields (and thus defect chemistries) in compositional space is important to synthesize new materials with optical and electronic properties controlled by defect chemistry and/or metastable compositions. Results for the second topic have shown that single crystal thin films can be formed on single crystal substrates with spin-on liquid precursors despite large differences in lattice parameters and/or crystal structures. Several mechanisms have been identified for the growth of single crystal thin films which are very different to the well know vapor phase epitaxy mechanisms. jg p.1

Descriptors :   *PRECURSORS, *CRYSTALLIZATION, *DIFFUSION, *SOLID SOLUTIONS, ELECTRONICS, OPTICAL PROPERTIES, LOW TEMPERATURE, QUICK REACTION, MICROSTRUCTURE, CRYSTAL STRUCTURE, SYNTHESIS, LIQUIDS, STRUCTURAL PROPERTIES, PROCESSING, HIGH TEMPERATURE, ELECTROMAGNETIC PROPERTIES, THIN FILMS, SINGLE CRYSTALS, EPITAXIAL GROWTH, SUBSTRATES, EQUILIBRIUM(GENERAL), SOLIDIFICATION, VAPOR PHASES, MECHANICS, CERAMIC MATERIALS, CHEMISTRY, METASTABLE STATE, SPINNERS.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Electrical and Electronic Equipment
      Ceramics, Refractories and Glass
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE