Grain-size effect on structure and phase transformations for barium titanate

Journal Article · Thu Aug 01 00:00:00 EDT 1996 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.54.3158· OSTI ID:286668

Frey, M H; Payne, D A ^[1]

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1. Department of Materials Science and Engineering, Seitz Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

We report the results of an investigation into the grain-size dependence of lattice structure for barium titanate (BaTiO{sub 3}) ceramics prepared by a sol-gel method. Raman and infrared spectroscopy, x-ray diffraction, and differential scanning calorimetry were used in combination with electron microscopy to study the evolution of lattice structure and phase transformation behavior with heat treatment and grain growth from the nano scale to the micron scale for BaTiO{sub 3} polycrystals. Raman spectroscopy and optical second-harmonic-generation measurements indicated the onset of local room-temperature acentric crystal symmetry with heat treatment and crystallite growth, well before the observation of any tetragonal structure by x-ray diffraction. Analysis of the room-temperature Raman spectra for ultrafine grain (grain size {lt}0.1 {mu}m) polycrystals suggested that a locally orthorhombic structure preceded the globally tetragonal form with grain growth. In support of this observation, differential scanning calorimetry suggested the orthorhombic-tetragonal phase transformation shifts up through room temperature with decreasing grain size. Hot-stage transmission electron microscopy studies revealed that fine grain (grain size {approx_equal}0.1 {mu}m) ceramics, which showed a thermal anomaly associated with the cubic-tetragonal phase transformation, were untwinned at room temperature, as well as on cycling through the normal Curie temperature, suggesting a single-domain state for individual grains. The findings are discussed in light of a number of possible causes, including the presence of processing-related hydroxyl defects and the effect of elastic constraints on phase transformation behavior for BaTiO{sub 3} grains in a polycrystalline microstructure. {copyright} {ital 1996 The American Physical Society.}

• Research Organization: Univ. of Illinois at Urbana-Champaign, IL (United States)
• DOE Contract Number: FG02-91ER45439
• OSTI ID: 286668
• Journal Information: Physical Review, B: Condensed Matter, Vol. 54, Issue 5; Other Information: PBD: Aug 1996
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM COMPOUNDS
PHASE TRANSFORMATIONS
TITANATES
ALKYLATING AGENTS
GRAIN SIZE
LATTICE PARAMETERS
CERAMICS
MICROSTRUCTURE
RAMAN SPECTRA
INFRARED SPECTRA
X-RAY DIFFRACTION
CALORIMETRY
HARMONIC GENERATION
CRYSTAL GROWTH
SOL-GEL PROCESS
BARIUM TITANATES
SECOND HARMONIC GENERATION
XRD
DSC