Accession Number:

ADA159279

Title:

Ferroelectric Tungsten Bronze Bulk Crystals and Epitaxial Thin Films for Electro-Optic Device Applications

Descriptive Note:

Semi-annual technical rept. no. 5, 1 Oct 1984-31 Mar 1985

Corporate Author:

ROCKWELL INTERNATIONAL CORP THOUSAND OAKS CA SCIENCE CENTER

Report Date:

1985-08-01

Pagination or Media Count:

54.0

Abstract:

Several doped ce3Ce4 and Fe2Fe3 and undoped SBN60 single crystals have been grown using the Czochralski technique. Optical evaluation shows that Ce-doped crystals have minimum or no striations and are of optical quality, while Fe-doped crystals are highly striated under all growth conditions. Current results suggest that the existence of striations depends strongly on the type of dopant and its location in the structure. Ce-doped SBN60 crystals currently exhibit excellent photorefractive properties with improved sensitivity and speed, indicating possible use for this material in device applications. The bronze composition SBN50 is being studied for pyroelectric IR focal plane array applications. SBN50 is slightly off congruent melting however using the current Czochralski technique is now possible to grow good quality crystals as large as 1 cm in diameter. An extensive discussion of the thermodynamic phenomenology for tungsten bronze crystals is presented. An excellent fit to birefringence polarization data for Ba2NaNb5015 BNN is found for the Devonshire form of the Gibbs free-energy expansion, and good agreement is found for a number of thermodynamic constants over a broad range of tungsten bronze materials. This indicates that the hypothesis of near-constant higher order stiffness parameters is a good approximation for tetragonal bronze ferroelectrics, thereby allowing the analysis of a very wide range of other bronze compositions.

Subject Categories:

  • Crystallography
  • Optics
  • Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE