Production of Spontaneous Polarization by Elastic Instabilities in Piezoelectric Materials.
Interim scientific rept.,
NEBRASKA UNIV LINCOLN BEHLEN PHYSICS LAB
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A systematic, theoretical investigation has been made of the stability of various piezoelectric and non-piezoelectric, polar structures as a function of the strength of the short-range repulsive interactions. In this way, the conditions under which a polarization wave can be frozen into these structures have been determined and certain general results with regard to lattice instabilities have been demonstrated analytically. These calculations have been supplemented by appropriate determinations of various material constants. Very marked differences are present between the behavior of piezoelectric and non-piezoelectric materials. Gadolinium molybdate GMO was selected for experimental investigation. Raman spectra for various orientations on poled and unpoled crystals were obtained for temperatures from near liquid nitrogen to above the 159C transition temperature, Tc. Preliminary results of optical absorption measurements to 70K and room temperature are reported. Results of studies of the pyroelectric behavior are described that indicate the ferroelectric phase transition to proceed in at least two distinctly different ways, energetically the difference, however, is less than .001 eV. Author
- Solid State Physics