Phonon scattering by ferroelectric domain walls in potassium dihydrogen phosphate

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7295842

Weilert, M A

The author has studied phonon scattering by ferroelectric domain walls in KH[sub 2]PO[sub 4] (KDP) using thermal conductivity and phonon imaging measurements of samples in both single-domain and multi-domain states. Domains were eliminated by applying a 2-3kV/cm field using evaporated electrodes. Phonon images of a poled (001) sample (at 1.7K) show two-fold symmetric focusing patterns that show the small orthorhombic distortion of the lattice. Poled images are qualitatively reproduced by calculations using continuum acoustics with room temperature tetragonal elastic moduli split to orthorhombic symmetry; a rough set of low temperature orthorhombic moduli is thereby determined. The presence of domains causes a large charge in ST focusing structures but little change in L and FT patterns. There is an apparent decrease in overall intensity for all modes. The images show strongly mode and polarization dependent phonon scattering. Monte Carlo simulations using acoustic mismatch to model phonon/domain wall interactions accurately reproduce the changes seen in the domained images. The low temperature (0.03-3K) thermal conductivity, k, of [100], [110], and [001] (tetragonal basis) oriented samples was measured. k in poled samples shows typical surface-limited behavior which is predicted to 13% by calculations including finite length and anisotropy and using elastic constants from the imaging simulations. Domain walls produce a 40% conductivity decrease in a [110] sample and a 30% decrease in [100] samples which is nearly independent of sample size. Domain wall scattering is nearly temperature independent between 0.3K and 1K, but decreases at lower temperatures, and increases above 1K. Acoustic mismatch calculations applied to k predict the right order of scattering, but do not reproduce the sample size effects. Orientation effects can be partially explained. The probability of diffuse scattering at the domain boundaries is at most 1%.

• Research Organization: Illinois Univ., Urbana, IL (United States)
• OSTI ID: 7295842
• Country of Publication: United States
• Language: English

Related Subjects

665400* -- Quantum Physics Aspects of Condensed Matter-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALI METAL COMPOUNDS
DOMAIN STRUCTURE
FERROELECTRIC MATERIALS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
OXYGEN COMPOUNDS
PHONONS
PHOSPHATES
PHOSPHORIC ACID
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
POTASSIUM PHOSPHATES
QUASI PARTICLES
SCATTERING
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
THERMAL BOUNDARY RESISTANCE
THERMAL CONDUCTIVITY
THERMODYNAMIC PROPERTIES