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Accession Number:
ADA076202
Title:
Magnetoferroelectrics, Divertable Ferroelectrics and Pyroelectric Glass Ceramics.
Descriptive Note:
Final rept. 22 Mar 76-21 Jun 79,
Corporate Author:
PENNSYLVANIA STATE UNIV UNIVERSITY PARK MATERIALS RESEARCH LAB
Report Date:
1979-06-21
Pagination or Media Count:
66.0
Abstract:
The highlight of the past three years was the discovery of magnetoferroelectricity, a new type of ferroelectricity caused by the ordering of magnetic spins in a low symmetry arrangement. A magnetoferroelectric develops a reversible spontaneous electric polarization on passing through a magnetic phase transition. The effect was demonstrated on Cr2BeO4 which undergoes a phase transformation from a centric paramagnetic state to a complex antiferromagnetic state at 28K. Ceramic specimens can be poled electrically below the transition temperature to a remnant polarization about five oders of magnitude smaller than BaTiO3. Additional magnetoferroelectric studies have been carried out on single crystals of CrBeO4 and on certain mixed crystals in the Fe2O3-Cr2O3 system. Second harmonic signals were observed from PbZrO3 ceramics, verifying the acentric nature of this important end member of the PZT system. Divertable ferroelectrics are an interesting group of materials in which the spontaneous polarization can be reoriented, but not reversed. The results of some experiments on nickel iodine boracite, and on barium titanium germanate are described. A new class of pyroelectric materials is reported. Carefully crystallized lithium silicate glass-ceramics are found to be pyroelectric.
Distribution Statement:
APPROVED FOR PUBLIC RELEASE
