Michael J. Haun

Thermodynamic theory of PbTiO3

A phenomenological thermodynamic theory of PbTiO3 was developed using a modified Devonshire form of the elastic Gibbs free energy. The spontaneous strain as a function of temperature was determined from pure sol‐gel derived PbTiO3 powder and used with selected data from the literature to determine the coefficients of the energy function. The theoretical prediction of the phase stability, spontaneous polarization and strains, and dielectric and piezoelectric properties agree well with experimental data. This theory provides a way of predicting the intrinsic single domain dielectric and piezoelectric properties of PbTiO3, which have not been completely determined from experimental measurements.

Thermodynamic theory of the lead zirconate-titanate solid solution system, part I: Phenomenology

Abstract Compositions within the lead zirconate-titanate (PZT) solid solution system have been extensively used in polycrystalline ceramic form in a wide range of piezoelectric transducer applications. However, the growth of good quality PZT single crystals for compositions across the entire phase diagram has not been accomplished. Due to the lack of single-crystal data, an understanding of the properties of polycrystalline PZT has been limited. If the single domain (intrinsic) properties of PZT could be determined, then the extrinsic contributions (e.g. domain wall and defect motions) to the polycrystalline properties could be separated from the intrinsic contributions. The purpose of this research has been to develop a thermodynamic phenomenological theory to model the phase transitions and single-domain properties of the PZT system. This paper is the first of a series of five papers describing the thermodynamic theory of PZT that has been developed for the entire solid solution system. In this paper th...

Thermodynamic theory of the lead zirconate-titanate solid solution system, part III: Curie constant and sixth-order polarization interaction dielectric stiffness coefficients

Abstract Vaiues of the Curie constant (C) and sixth-order polarization interaction dielectric stiffness coefficients (α112 and α123) are needed for the development of a thermodynamic theory for the entire lead zirconate-titanate (PZT) solid solution system. Low-temperature dielectric data measured on pure homogeneous polycrystalline PZT samples were used to determine values of these coefficients at several compositions across the phase diagram. Equations were then fitted to these data to determine the compositional dependence of the coefficients. The Curie constant was found to form a peak in the middle of the phase diagram at the PZT 50/50 composition.

Thermodynamic theory of the lead zirconate-titanate solid solution system

Abstract Compositions within the lead zirconate-titanate (PZT) solid solution system have been extensively used in polycrystalline ceramic form in a wide range of piezoelectric transducer application. However, the growth of good quality PZT single crystals for compositions across the entire phase diagram has not been accomplished. Due to the lack of single crystal data, an understanding of the properties of ceramic PZT has been limited. If the single domain (intrinsic) properties of PZT could be determined, then the extrinsic contributions (e.g., domain wall and defect motions) to the ceramic properties could be separated from the intrinsic contributions. The purpose of this research has been to develop a thermodynamic phenomenological theory to model the phase transitions and single domain properties of the PZT system. A two-sublattice theory, where each sublattice has a separate polarization, was used to account for the ferroelectric and antiferroelectric phases. An additional order parameter was also i...

Composition and temperature dependence of the dielectric, piezoelectric and elastic properties of pure PZT ceramics

Pure (undoped) piezoelectric lead zirconate titanate (PZT) ceramic samples at compositions across the ferroelectric region of the phase diagram were prepared from sol-gel-derived fine powders. Excess lead oxide was included in the PZT powders to obtain dense (95-96% of theoretical density) ceramics with large grain size (>7 mu m) and to control the lead stoichiometry. The dielectric, piezoelectric, and elastic properties were measured from 4.2 to 300 K. At very low temperatures, the extrinsic domain wall and thermal defect motions freeze out. The low-temperature dielectric data can be used to determine coefficients in a phenomenological theory. The extrinsic contribution to the properties can then be separated from the single-domain properties derived from the theory.<<ETX>>

Modeling of the electrostrictive, dielectric, and piezoelectric properties of ceramic PbTiO/sub 3/

The upper and lower limits of the electrostrictive constants, dielectric permittivities, spontaneous polarizations, and piezoelectric coefficients were calculated for ceramic PbTiO/sub 3/ from theoretical single-crystal constants. Experimental ceramic data fall between these upper and lower limits. The large piezoelectric anisotropy d/sub 33//d/sub 31/ of ceramic PbTiO/sub 3/ was shown to be related to the single-crystal PbTiO/sub 3/ electrostrictive anisotropies Q/sub 11//Q/sub 12/ and Q/sub 44//Q/sub 12/. The possibility of a change in sign of the ceramic d/sub 31/ coefficient due to a slight variation in the single-crystal electrostrictive anisotropies was discussed. The single-crystal and predicted ceramic hydrostatic electrostrictive constants were found to be equal. Using this result the ceramic hydrostatic g/sub h/ coefficient is always smaller than the single-crystal g/sub h/, but the ceramic hydrostatic d/sub h/ coefficient can be either larger or smaller than the single-crystal d/sub h/ depending on the dielectric anisotropy ( epsilon /sub 11// epsilon /sub 33/) of the single-crystal.<<ETX>>

Densification, crystallization, and electrical properties of lead zirconate titanate glass-ceramics

Piezoelectric glass-ceramics in the lead zirconate titanato-lead silicate system were developed. SiO/sub 2/ was required for glass formability, and excess PbO allowed low temperature processing. The amounts of those constituents were limited by the optimization of the piezoelectric properties. Only a small region of compositions in this system yielded the desired combination of glass formability, crystallization and densification behavior, and resulting piezoelectric properties. Selected compositions were melted and roller quenched to form glass ribbon, then milled into glass powder. Pressed glass powder densified to closed porosity at 850/spl deg/C with piezoelectric d/sub 33/ and g/sub 33/ coefficients of 26 pC/N and 33/spl times/10/sup -3/ Vm/N. The low temperature sintering behavior of these ferroelectric glass-ceramics provides the possibility of incorporating a piezoelectric material as a sensor or actuator in thick film circuits or low-fire multilayer packages.