Quantum ferroelectricity in K/sub 1-x/Na/sub x/TaO/sub 3/ and KTa/sub 1-y/Nb/sub y/O/sub 3/

Journal Article · Sun Jul 01 04:00:00 EDT 1979 · Phys. Rev., B: Condens. Matter; (United States)

OSTI ID:6104451

Hoechli, U T; Boatner, L A

The effect known as ferroelectricity arises when forces between polarizable ions in a solid produce a spontaneous displacement of these ions which results in a lattice polarization below some characteristic (Curie) temperature. Fluctuations in this polarization may be thermally induced as in the case of classical ferroelectrics, or if the Curie temperature is near 0 K, the fluctuations can be due to quantum-mechanical zero-point motion. The term ''quantum ferroelectric'' is applied to those systems where fluctuations in the polarization result from the zero-point motion. Experimental determinations of variations in the dielectric constant, spontaneous polarization, and elastic compliance as a function of temperature and impurity concentration are reported for K/sub 1-x/Na/sub x/TaO/sub 3/ and KTa/sub 1-y/Nb/sub y/O/sub 3/, and these results show that the physical properties of quantum ferroelectrics differ from those of classical ferroelectrics in the following ways: First, for a quantum ferroelectric, the transition temperature depends on impurity concentration (i.e., on an effective order parameter) as T/sub c/ proportional (x-x/sub c/)/sup 1/2/, as opposed to T/sub c/ proportional (x-x/sub c/) for the classical case. Second, the inverse dielectric constant varies with temperature as epsilon/sup -1/ proportional T/sup 2/ for the quantum-mechanical case, instead of epsilon/sup -1/ proportional T. Finally, the distribution of transition temperatures in a given macroscopic sample with a Gaussian impurity concentration distribution is p (T/sub c/) proportional T/sub c/ exp(-..cap alpha..T/sup ts4//sub c/) for the quantum ferroelectric, as opposed to a Gaussian for the classical situation. These results are in agreement with previous theoretical predictions of some of the distinguishing characteristics of quantum ferroelectricity.

• Research Organization: IBM Zurich Research Laboratory, 8803 Rueschlikon, Switzerland
• OSTI ID: 6104451
• Journal Information: Phys. Rev., B: Condens. Matter; (United States), Journal Name: Phys. Rev., B: Condens. Matter; (United States) Vol. 20:1; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALI METAL COMPOUNDS
CHALCOGENIDES
CURIE POINT
DIELECTRIC MATERIALS
DIELECTRIC PROPERTIES
ELASTICITY
ELECTRICAL PROPERTIES
ELECTRICITY
FERROELECTRIC MATERIALS
IMPURITIES
MATERIALS
MECHANICAL PROPERTIES
NIOBIUM COMPOUNDS
NIOBIUM OXIDES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PIEZOELECTRICITY
POLARIZATION
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
SODIUM COMPOUNDS
SODIUM OXIDES
TANTALUM COMPOUNDS
TANTALUM OXIDES
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE