Accession Number:

ADA065770

Title:

Improper Ferroelectrics. Structural Studies of LiNH4SO4

Descriptive Note:

Final technical rept. 1 Jun 1977-31 May 1978

Corporate Author:

ILLINOIS UNIV AT CHICAGO CIRCLE DEPT OF PHYSICS

Personal Author(s):

• Raccah, Paul M.
• Kouvel, James S.
• Maglic, Rastko C.

Report Date:

1978-12-01

Pagination or Media Count:

24.0

Abstract:

The room temperature crystal structure of LiNH4SO4, complete with the positions of the hydrogen ions, has been determined from neutron diffraction measurements. X-ray diffraction study has shown that the abrupt ferroelectric transition of LiNH4SO4 near 11 C involves a doubling of the orthorhombic unit cell normal to the polar axis. The phonon dispersion in this material above the transition temperature was explored by means of inelastic neutron scattering, but no soft phonon mode associated with the structural transition could be found.

Descriptors:

• *AMMONIUM COMPOUNDS
• *CRYSTAL STRUCTURE
• *LITHIUM COMPOUNDS
• *SULFATES
• BRILLOUIN ZONES
• DEUTERIUM
• FERROELECTRIC CRYSTALS
• HYDROGEN
• INELASTIC SCATTERING
• ISOTOPE EFFECT
• NEUTRON DIFFRACTION
• PHASE TRANSFORMATIONS
• PHONONS
• POSITION FINDING
• THERMAL PROPERTIES
• X RAY DIFFRACTION

Subject Categories:

• Inorganic Chemistry
• Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE