Accession Number : ADA322553

Title :   Synthesis of Ceramics from Solutions: Functionally Graded Composites, NanoComposites and Single Crystal Thin Films. Lattice Mismatch Accommodation in Perovskite Films on Perovskite Substrates.

Descriptive Note : Technical rept. no. 3, Dec 95-Nov 96,

Corporate Author : CALIFORNIA UNIV SANTA BARBARA COLL OF ENGINEERING

Personal Author(s) : Langjahr, P. A. ; Lange, F. F. ; Wagner, T. ; Ruehle, M.

PDF Url : ADA322553

Report Date : 28 FEB 1997

Pagination or Media Count : 37

Abstract : Cubic perovskite films with different compositions were grown on perovskite substrates to investigate the influence of a large lattice mismatch on growth phenomena via the chemical solution deposition method, using toluene solutions of different 2-ethylhexanoates and neodecanoates. The films were pyrolyzed to crystallize the perovskite of the desired composition and then heated to 1000 deg C to promote epitaxial grain growth. Pole figures obtained via X-ray diffraction as well as selected area diffraction (SAD) of TEM specimen with lattice mismatches of 2.5% (SrTi(0.5)Zr(0.5)O3 on SrTiO3), 5% (SrZrO3 on SrTiO3), 7.4% (BaZrO3 on SrTiO3) and 8.2% (SrZrO3 on LaAlO3) reveal only the epitaxial orientation 100(001) film (parallel lines) 100(001) substrate. The XRD and TEM results also indicate increasing polycrystallinity with increasing lattice mismatch. High resolution electron microscopy (HREM) of films on SrTiO3 demonstrated that an array of misfit dislocations is present at the interface. The misfit dislocations have line vectors 1 of a<100>-type and Burgers-vectors b of a<010>- type. Dislocation separation distances obtained with HREM and XRD lattice parameter measurements show that the strain energy within the films, due to lattice mismatch, is nearly fully relaxed. The mechanisms of epitaxial growth and dislocation formation are discussed.

Descriptors :   *COMPOSITE MATERIALS, *THIN FILMS, *SUBSTRATES, *CERAMIC MATERIALS, *PEROVSKITES, SYNTHESIS, X RAY DIFFRACTION, EPITAXIAL GROWTH, HIGH RESOLUTION, ELECTRON MICROSCOPY, DEPOSITION, DISLOCATIONS, DIFFRACTION, OXIDES, ALUMINUM, SEPARATION, ZIRCONIUM, BARIUM, STRONTIUM, TITANATES, LANTHANUM, GRAIN GROWTH, ALUMINATES, TOLUENES.

Subject Categories : Geology, Geochemistry and Mineralogy
      Inorganic Chemistry
      Ceramics, Refractories and Glass
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE