Actions for ELECTRICAL AND THERMAL MEASUREMENTS ON FE-AFE PHASE TRANSITIONS IN LEAD HAFNATE TITANATE COMPOSITIONS. Final Report
ELECTRICAL AND THERMAL MEASUREMENTS ON FE-AFE PHASE TRANSITIONS IN LEAD HAFNATE TITANATE COMPOSITIONS. Final Report
- Author
- Northrip, J. W.
- Published
- United States : [publisher not identified], 1963.
[Oak Ridge, Tennessee] : [U.S. Atomic Energy Commission], 1963. - Physical Description
- microfiche : negative ; 8 x 13 cm
- Additional Creators
- Baum, G. A. and Kohnke, E. E.
- Summary
- Electrical and Thermal Measurements. Investigations have been carried out to determine the characteristics of ferroelectric and antiferroelectric transitions in lead perovskites. Materials studied include solid solutions of lead zirconate titanate, lead zirconate titanate stannate, and lead hafnate titanate. These solid solutions were chosen because compositions among them possess a ferroelectric-to-antiferroelectric transition with rising temperature while others display an antiferroelectric-toferroelectric transition under the same conditions. Dielectric constant and loss were determined as functions of temperature and applied electric field, with an emphasis being placed on the use of loss conductance rather than tan delta as a method of examining the loss mechanisms in these materials. By this technique, the variation of transition temperature with external electric field was determined. The decrease of peak dielectric constant with external field characteristic of dielectric saturation was found to be especially prominent in transitions involving a ferroelectric phase. Hysteresis measurements were made primarily in an effort to separate the antiferroelectric double loop behavior from the normal ferroelectric loops near transitions. It was found that parts of some samples retained ferroelectric character many degrees above the normal transition temperature. Measurements of specific heat as a function of temperature were used to determine the relative free energies and entropies of the phases. From the results of these studies it appears that the reversal of transition direction mentioned above results from very slight shifts in the relative magnitudes of the free energy and the entropy of the ferroelectric and antiferroelectric phases of these materials, rather than from some wide change in their structural or chemical character. Dispersion of Dielectric Characteristics. The frequency dependence of the dielectric parameters of some polycrystalline materials exhibiting ferroelectricity and/or antiferroelectricity was examined under varying conditions of temperature and static electric field. Work was performed in the frequency range from 10/sup 2/ to 10/sup 5/ cps on lead zirconate stannate titanate and lead hafnate tithnate solid solutions. The dielectric constant and equivalent conductance'' were determined over a range of temperatures extending from 20 deg C to 200 deg C and up to field strengths of 8 kv/cm although the most extensive measurements were made at room temperature and zero fteld. Both ferroelectric and antiferroelectric phases of the materials were investigated and the trends of the results compared. The samples in general showed a loglinear decrease in dielectric constant with increasing frequency. The antiferroelectric samples displayed a decrease approximately one-third to one-haif that of the ferroelectric materials. For all samples, the equivalent conductance values plotted on a log-log scale against frequency yielded a straight line with a slope of very nearly one, suggesting the presence of hysteresis-type losses. These variations with frequency could be altered in various degree by changing temperature or field. Using as a basis the apparert hysteresis-type loss mechanism, a model is proposed which explains the equivalent conductance results and also remains consistent with the dispersion in the dielectric constant. The model involves the concept of minute polarization reversals by domain wall motion. The results at varying temperatures and field strengths are also incorporated into the model. The experimental findings for both the ferroelectric and antiferroelectric compositions show a great deal of consistency with the model, and with this as a foundation, it is suggested that perhaps the solid solution samples are neither purely ferroelectric nor purely antiferroelectric but rather a combination of the two phases with one more dominant. (auth)
- Report Numbers
- SC-DC-64-344
- Other Subject(s)
- Antiferroelectricity
- Coupling
- Crystals
- Diagrams
- Dielectrics
- Diffraction
- Diffusion
- Electric conductivity
- Electric fields
- Electricity
- Energy levels
- Energy
- Entropy
- Ferroelectric materials
- Ferromagnetic materials
- Free energy
- Frequency
- Gamma radiation
- Hafnium compounds
- Hysteresis
- Interactions
- Lead compounds
- Lead
- Losses
- Mathematics
- Measured values
- Motion
- Nuclear models
- Nuclear theory
- Nuclei
- Nucleons
- Physics
- Polarization
- Quantitative analysis
- Solid solutions
- Specific heat
- Spin
- Temperature
- Thermodynamics
- Tin compounds
- Titanium oxides
- Transients
- Transitions
- Variations
- Zirconium compounds
- Collection
- U.S. Atomic Energy Commission depository collection.
- Note
- DOE contract number: AT(29-1)-789
NSA number: NSA-18-018458
OSTI Identifier 4037545
Research organization: Oklahoma State Univ., Stillwater, OK. Research Foundation. - Funding Information
- Sponsored by US Atomic Energy Commission (AEC).
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