Accession Number:

ADA250089

Title:

Optimized Photorefractive Barium Titanate

Descriptive Note:

Final rept. 20 Feb 1987-31 May 1990,

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE

Personal Author(s):

Report Date:

1992-03-11

Pagination or Media Count:

100.0

Abstract:

The goal of this research program was to investigate new and modified crystal-growth techniques that would lead to high-optical-quality BaTiO3 with increased photorefractive speed and sensitivity. The research program consisted of 1 feed material purification, 2 crystal growth by the top-seeded-solution technique as well as by a barium borate flux technique, 3 new furnace design studies and 4 photorefractive characterization experiments. Iron and nickel- doped BaTiO3 crystals were grown under the program. BaTiO3 is a promising photorefractive material due to its large electrooptic coefficient and excellent self-pumped phase conjugation. Our furnaces were limited by certain design and operating characteristics, and crystals grown in these furnaces were easily contaminated by the furnace itself. Two new furnaces, cylindrical and octagonal furnaces, were developed with commercially available parts that are cleaner, more mechanically reproducible , more uniform in temperature and more responsive to control action through reduced thermal mass. The two furnaces are equipped with precise computer control of the pulling and rotation system. The cylindrical furnace was found to be susceptible to cracking due to expansion when heated and to shrinkage after heating. To prevent cracking, expansion joints were provided and the insulation set was made of flat plates set up in an octagonal pattern. In order to widen the scope of BaTiO3 growth, we investigated the BaO-B203-TiO2 system, which, compared to the conventional BaO-TiO2 System, would allow crystallization under different chemical condition at a lower temperature and over a wider range of Ba to Ti ratio.

Subject Categories:

  • Inorganic Chemistry
  • Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE