Antiferroelectric Transition Research Articles

Ferrielectricity in Copper Formate Tetrahydrate

An additional phase transition in Cu(HCOO) 2 ·4H 2 O has been found at -46°C below the well-known antiferroelectric transition at -38°C. A distinct anomaly in pyroelectric current was observed at the new transition. Ferrielectric triple loop was obtained along b axis in the low temperature phase. Respective temperatures are shifted to higher temperature by 10°C for Cu(HCOO) 2 ·4D 2 O. Though the net polarization is small and the phase is approximately antiferroelectric, the phase below -46°C is ferrielectric.

Stress effects in two modified lead zirconate titanate ferroelectric ceramics

Mechanical properties of ferroelectric ceramics with compositions Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 and Pb0.97La0.02(Zr0.92Ti0.08)O3 have been studied as functions of both hydrostatic pressure and uniaxial stress. Measurements of ultrasonic velocity and sample strains have been made in order to characterize unpoled samples. Both materials have pressure-induced ferroelectric (FE) to antiferroelectric (AFE) phase transitions at ∼0.2 GPa of hydrostatic pressure. Under uniaxial-stress conditions two effects are observed: rotation of FE domains and the FE–AFE phase transition. These effects are separately resolved by the measurements, even though they occur in overlapping stress regions. The domain reorientation responses of the two materials appear to be nearly identical, but the FE–AFE transition begins at lower stress levels for the Nb-doped material. This is presumably due to that material transforming into the orthorhombic (PbZrO3) phase, whereas the La-doped material transforms into the tetragonal AFE phase. The phase transition is spread over a broad range of uniaxial stress for each material and is not nearly complete by 0.6 GPa, the highest stress level attainable. Possible implications of the results for shock-wave studies of FE ceramics are briefly discussed.

Ultrasonic Study of NaNO2. I. Anisotropic Character of Elastic Constants and Attenuation Coefficients

The temperature dependence of the elastic constants c 11 , c 22 , c 33 , c 44 , c 55 and c 66 of NaNO 2 was determined in the wide temperature range from 20 to 200°C. Near the antiferroelectric transition temperature ( T N ), c 33 , c 44 , c 55 and c 66 are rather normal and show a slight bending at T N . On the other hand c 11 and c 22 show softening towards T N . Corresponding to the anisotropic behavior of the elastic constants, the ultrasonic attenuation coefficients associated with c 11 and c 22 exhibit critical behavior and those associated with c 33 and c 55 show normal temperature dependence. The above character in the elastic properties can be explained in terms of the anisotropic coupling constants between the elastic strains and the staggered polarization expected from a crystal symmetry consideration.

Pressure-temperature phase diagrams for several modified lead zirconate ceramics

Using dielectric constant and loss measurements we have determined the pressure-temperature phase diagrams of four ferroelectric ceramics based on lead zirconate (PbZrO 3). The materials chosen for study all have pressure-induced ferroelectric to antiferroelectric transitions at ∼0.3 GPa. In all four materials, five phases were identified by comparing our results with studies, previously published by other workers, of the phase behavior of modified PbZrO 3 materials as a function of composition and temperature. The observed phases are the ideal cubic perovskite paraelectric phase, two rhombohedral ferroelectric phases, and two antiferroelectric phases, one orthorhombic and one pseudotetragonal. Comparison is made with previous temperature-composition studies of modified PbZrO 3 materials.

Bias Effect on the Antiferroelectric Transition

For the antiferroelectric transition, three phases, antipolar, nonpolar and polar were considered under bias field with comparisons to the phenomenological theory previously developed. Bias effect on the antipolar to nonpolar transition is zero to the first order approximation, and the shift of the transition to the lower temperature is quadratic to applied field. Under strong field, succesive transitions, antipolar-polar-nonpolar, appear, where the antipolar-polar transition is shifted to the lower temperature by increasing bias. The shift of the polar-nonpolar transition to the higher temperature by bias is much smaller than that of the former transition. These results were confirmed in ADP and CFT experimentally. A mere shift to the lower temperature by bias field could not be taken as an indication of the antipolar-nonpolar (antiferroelectric) transition, which has been believed so far. The field dependence of the shift must be checked.

Deuteron NMR Study of the Role of Ammonium Ions in the Antiferroelectric Transition in ND4D2AsO4

physica status solidi (a)Volume 40, Issue 2 p. K121-K125 Miscellaneous Deuteron NMR Study of the Role of Ammonium Ions in the Antiferroelectric Transition in ND4D2AsO4 R. Blinc, R. Blinc J. Stefan Institute, University of LjubljanaSearch for more papers by this authorJ. Slak, J. Slak J. Stefan Institute, University of LjubljanaSearch for more papers by this authorM. Luzar, M. Luzar J. Stefan Institute, University of LjubljanaSearch for more papers by this author R. Blinc, R. Blinc J. Stefan Institute, University of LjubljanaSearch for more papers by this authorJ. Slak, J. Slak J. Stefan Institute, University of LjubljanaSearch for more papers by this authorM. Luzar, M. Luzar J. Stefan Institute, University of LjubljanaSearch for more papers by this author First published: 16 April 1977 https://doi.org/10.1002/pssa.2210400246Citations: 8AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume40, Issue216 April 1977Pages K121-K125 RelatedInformation

Suppression of antiferroelectricity in TiSe2 by excess carriers

Analysis of the optical reflectivity spectra of TiSe2 at room temperature shows that the lattice polarizabilitye t * as well as the electronic polarizability ɛ∞ are unusually large. This suggests to us that the phase transition atT 0=200 K is a phonon-driven antiferroelectric transition. The properties of such a soft-mode transition in a semi-metal are investigated. It is found that excess carriers suppress the transition and that the excess resistivity at the transition varies as |T−T 0|−1.

Low-temperature polarization in impure SrTiO3 ceramics

Measurements of the temperature dependence of the dielectric constant and polarization in a constant field have been made on nominally pure SrTiO3 ceramics and SrTiO3 ceramics containing vanadium and niobium impurities. The peaks in the dielectric constant and the remanent polarization observed are apparently not due to a ferroelectric or antiferroelectric transition but rather to the presence of a thermoelectret state existing for permanent dipoles in the materials. It is suggested that the permanent dipoles have an origin similar to the impurity-vacancy dipoles found in alkali halides.

The F Center Emission in KCN

The excitation and emission spectrum for the F centers in KCN are presented. The blue-shift in emission peak is observed below anti-ferroelectric transition temperature. The thermal ionization probability from the RES is estimated with the activation energy of 0.070 eV and the frequency factor of (3.0±0.1)×10 4 τ R -1 , where τ R is the radiative life time of the RES.

Dielectric and thermal properties of Pb2Nb2O7 at low temperature

Measurements of the dielectric constant, polarization, zero-field specific heat, and field-dependent specific heat of polycrystalline Pb2Nb2O7 at low temperatures are reported. No evidence for a phase transition at 15 K was found, contrary to previous suggestions of an antiferroelectric transition at 15 K based on dielectric data. The peak in the dielectric constant appears to be due to relaxation phenomena.

Phenomenological Treatment of Antiferroelectric Transition under Hydrostatic Pressure

By applying Kittel's antiferroelectric polarizations (Pa and Pb) and Cross' ferroelectric polarization Pm and antiferroelectric polarization Pn to the free energy function for ferroelectrics under hydrostatic pressure, the Gibbs function for antiferroelectrics under hydrostatic pressure is given in terms of the pressure, polarization and electric field. On the basis of this energy function, dielectric properties such as the pressure dependence of permittivity or spontaneous polarization and the electric field dependence of permittivity are clearly explained, and the so-called double hysteresis loop under hydrostatic pressure is explained fairly well for antiferroelectrics of the second and the first order transitions. Moreover, these analyses are confirmed to be appropriate by comparing with the experimental results for antiferroelectric Pb2MgWO6, etc.

Phase transitions and lattice dynamics in Ag2H3IO6 and (NH4)2H3IO6

The investigation of thermal, optical and dielectric properties of Ag2H3IO6 and (NH4)2H3IO6 revealed phase transitions in two steps with unknown intermediate phases. Reflectivity measurements in the far infrared region confirm that the main step is caused by a freezing in of the proton tunnelling modes. From the results of NMR-NQR-spectroscopy the low temperature structures for both compounds are deduced. The complete group analysis of lattice vibrations and proton ordering modes of the room temperature phases is performed. In the case of Ag2H3IO6 the transitions can be discussed in the frame-work of the Landau theory, starting with a condensation of an antiphase vibration of the silver atoms in theF point of the trigonal Brillouin zone, whereas in the case of (NH4)2H3IO6 a simultaneous ordering of protons inZ, F, andL-points of the Brillouin zone is proposed for the first step. A new definition of antiferroelectric transitions is suggested which is based on symmetry arguments only. The proton-ordering transitions in both compounds can then be classified as antiferroelectric.

Theory of the antiferroelectric transition in copper formate tetrahydrate

The basic dimer model for copper formate tetrahydrate has been extended recently by Ishibashi, Ohya and Takagi (1973) by adding mean-field interactions to account for both interplanar and further-neighbour intraplanar interactions. However, the present use of exact calculations for the basic model gives substantially different values for the interaction strengths when compared with the Bethe approximation for the basic model used by these workers. The calculation is extended to include the electric field and obtain a phase diagram with four phases, all separated by first-order phase lines. Although the dielectric data can be fitted reasonably well with this model, it is impossible to obtain agreement with the experimental latent heat and the discontinuity observed in the specific heat. The calculations support the idea that the transition in Cu(HCOO)2.4H2O is primarily two dimensional, because the ratio of the interplanar to intraplanar interaction is about 10-3.

The antiferroelectric transition in thiourea studied by thermal neutron scattering

The neutron scattering from deuterated thiourea, SC(ND2)2, was examined in the antiferroelectric and paraelectric phases using single crystals mounted on triple-axis spectrometers. The long-period order in the antiferroelectric phase gives rise to satellite Bragg peaks, the intensities of many of which were measured in the (hkO) and (Okl) zones. A model of the structure in which the lattice contains a sinusoidal displacement of the molecules as rigid units was developed and fitted to the data with reasonable success. Quasi-elastic diffuse scattering was detected in phase V which was strongly temperature dependent. A mechanism for the transition based on an overdamped soft rotational lattice mode is presented and supported by calculations of the Coulomb lattice energy of a thiourea crystal distorted by such a mode as a function of the wavevector. The temperature dependence of the relaxation time of the ferroelectric mode is given.

Erratum: Static and dynamic properties of the structural phase transitions in NaNbO3

The static and dynamic properties which characterize the structural phase transitions in NaNb${\mathrm{O}}_{3}$ have been widely investigated by transient NMR measurements of the ${\mathrm{Na}}^{23}$ and ${\mathrm{Nb}}^{93}$ nuclei in a powdered sample (no large-enough single crystal was available). The temperature range investigated (100-1100 \ifmmode^\circ\else\textdegree\fi{}K) includes both the purely structural transitions associated with the tilting of the Nb${\mathrm{O}}_{6}$ octahedra and the ferroelectric and antiferroelectric transitions associated with the off-center motion of the Nb atoms. The static effects have been investigated through the changes in the free-precession decay of the central line due to second-order quadrupole broadening. The dephasing time of the free-precession decay has been related to the quadrupole coupling constant. The temperature dependence of the rotational displacement of the Nb${\mathrm{O}}_{6}$ octahedra and of the off-center displacement of the Nb ions is then obtained. The variation of the tilt angle $\ensuremath{\phi}$ of the oxygen octahedra near the transition at 641 \ifmmode^\circ\else\textdegree\fi{}C is very rapid and it is not possible to decide whether $\ensuremath{\phi}$ goes to zero continuously or with a small discontinuity. The maximum value of $\ensuremath{\phi}$ in the tetragonal phase, as deduced from a crude estimate of the electric field gradient in a point-charge model, is about 7\ifmmode^\circ\else\textdegree\fi{}. No off-center displacement of the Nb atom is observed, on cooling, before the 480 \ifmmode^\circ\else\textdegree\fi{}C transition. The numerical values for the Nb displacements in the $R$ and $P$ phase ($\ensuremath{\sim}0.11$ \AA{} at 373 \ifmmode^\circ\else\textdegree\fi{}C and $\ensuremath{\sim}0.15$ \AA{} at 315 \ifmmode^\circ\else\textdegree\fi{}C) are in good agreement with previous indications of x-ray diffraction measurements. The dynamic effects have been investigated through nuclear spin-lattice quadrupole relaxation. A theory is developed which relates the relaxation rate to the critical parameters of the central peak in the dynamic cubic-tetragonal phase transition at 641 \ifmmode^\circ\else\textdegree\fi{}C, a value $\ensuremath{\nu}\ensuremath{\simeq}0.6$ for the critical index of the correlation length can be estimated; the rotational fluctuations appear to have a quasiplanar correlation. The experimental results seem to indicate that for $(T\ensuremath{-}{T}_{c})\ensuremath{\sim}4$ \ifmmode^\circ\else\textdegree\fi{}C the slowing down reaches an angular frequency of the order of 300 MHz. Finally, an estimate for the root-mean-square local fluctuating angle near ${T}_{c}$ of about 1.6\ifmmode^\circ\else\textdegree\fi{} is obtained.

The Raman spectrum of copper formate tetrahydrate. II

The Raman spectrum of copper formate tetrahydrate Cu(COOH)2.4H2O, has been determined in the range 3500 to 79 cm-1 from 90 to 250 K. Several lines are found to disappear rather abruptly as the antiferroelectric transition temperature 235.5 K is crossed. By comparison with the spectrum of the deuterate, Cu(COOH)2.4D2O, at 90 K, some of these lines are identified as translatory and rotatory water modes. This agrees with crystallographic and other evidence that ordering of the water molecules occurs at the phase transition. Although most internal modes do not change significantly from 90 to 250 K, the symmetric stretching mode of water at 3092 cm-1 broadens slightly and decreases appreciably in peak intensity.

Phenomenological Theory of Antiferroelectric Transition. III. Phase Diagram and Bias Effects of First-Order Transition

Kittel's free energy expression with the cross term of two sublattice polarizations was dealt with to obtain some properties of a linear antiferroelectric. Four phases, nonpolar, polar, antipolar and semipolar, are stable in proper ranges of temperature and bias field. The phase diagram was obtained by comparisons of free energy of four phases. The isothermal relation between the polarization and the external field predicted successive forced transitions and a multiple hysteresis loop. At a constant field, the antipolar-polar-semipolar-nonpolar transitions were expected at changing temperature. Correspondingly to the transition scheme, complicated behaviors of polarization, antipolarization and susceptibility as functions of temperature were calculated with bias field as a parameter.

Spin-lattice relaxation in the rotating frame and extreme slowing-down at the antiferroelectric transition in copper formate tetrahydrate

The effect on the temperature behavior of the spin-lattice relaxation rates in laboratory and rotating frames in presence of extreme slowing-down of the critical fluctuations in an Ising-type system is discussed. Proton spin-lattice relaxation measurements of T 1 and T 1ϱ in water-deuterated copper formate tetrahydrate are presented. The data shown that the anomalous behavior of the proton T 1ϱ in the neighbourhood of the antiferroelectric phase transition recently observed by Zumer and Pirš in the ordinary crystal cannot be ascribed to the critical slowing-down of the water molecules. A possible interpretation on the basis of a mechanism of creation and annihilation of paramagnetic excitons is discussed.

Static and dynamic properties of the structural phase transitions in NaNbO3

The static and dynamic properties which characterize the structural phase transitions in NaNb${\mathrm{O}}_{3}$ have been widely investigated by transient NMR measurements of the ${\mathrm{Na}}^{23}$ and ${\mathrm{Nb}}^{93}$ nuclei in a powdered sample (no large-enough single crystal was available). The temperature range investigated (100-1100 \ifmmode^\circ\else\textdegree\fi{}K) includes both the purely structural transitions associated with the tilting of the Nb${\mathrm{O}}_{6}$ octahedra and the ferroelectric and antiferroelectric transitions associated with the off-center motion of the Nb atoms. The static effects have been investigated through the changes in the free-precession decay of the central line due to second-order quadrupole broadening. The dephasing time of the free-precession decay has been related to the quadrupole coupling constant. The temperature dependence of the rotational displacement of the Nb${\mathrm{O}}_{6}$ octahedra and of the off-center displacement of the Nb ions is then obtained. The variation of the tilt angle $\ensuremath{\phi}$ of the oxygen octahedra near the transition at 641 \ifmmode^\circ\else\textdegree\fi{}C is very rapid and it is not possible to decide whether $\ensuremath{\phi}$ goes to zero continuously or with a small discontinuity. The maximum value of $\ensuremath{\phi}$ in the tetragonal phase, as deduced from a crude estimate of the electric field gradient in a point-charge model, is about 7\ifmmode^\circ\else\textdegree\fi{}. No off-center displacement of the Nb atom is observed, on cooling, before the 480 \ifmmode^\circ\else\textdegree\fi{}C transition. The numerical values for the Nb displacements in the $R$ and $P$ phase ($\ensuremath{\sim}0.11$ \AA{} at 373 \ifmmode^\circ\else\textdegree\fi{}C and $\ensuremath{\sim}0.15$ \AA{} at 315 \ifmmode^\circ\else\textdegree\fi{}C) are in good agreement with previous indications of x-ray diffraction measurements. The dynamic effects have been investigated through nuclear spin-lattice quadrupole relaxation. A theory is developed which relates the relaxation rate to the critical parameters of the central peak in the dynamic cubic-tetragonal phase transition at 641 \ifmmode^\circ\else\textdegree\fi{}C, a value $\ensuremath{\nu}\ensuremath{\simeq}0.6$ for the critical index of the correlation length can be estimated; the rotational fluctuations appear to have a quasiplanar correlation. The experimental results seem to indicate that for $(T\ensuremath{-}{T}_{c})\ensuremath{\sim}4$ \ifmmode^\circ\else\textdegree\fi{}C the slowing down reaches an angular frequency of the order of 300 MHz. Finally, an estimate for the root-mean-square local fluctuating angle near ${T}_{c}$ of about 1.6\ifmmode^\circ\else\textdegree\fi{} is obtained.

Dimer models for the antiferroelectric transition in copper formate tetrahydrate

This paper develops the lattice statistical theory of the antiferroelectric transition in copper formate tetrahydrate in terms of dimer and 8-vertex models. The simplest dimer model is shown to be inappropriate for describing the transition, primarily because the hydrogens order into the wrong ground-state configuration. In the context of the dimer model, we introduce two exactly solvable modifications by postulating additional, physically plausible short-range interactions in the hydrogen bonding. The first model, which results from asymmetrically weighting the dimer positions, does have the observed ``frozen'' ground state and residual short-range order above Tc, but the transition is continuous. The second model introduces repulsive interactions between nearest-neighbor parallel dimer positions via the Baxter formulation of the dimer model in terms of the 8-vertex model. A suitable lattice transformation enables us to develop the model in terms of a generalized KDP model. This model has a first-order transition with a maximum allowable transition entropy of 0.876 cal/deg · mole, in excellent agreement with that determined from specific heat measurements. The higher energy hydrogen configurations are of the order of kT, indicative of the nature of the thermal excitations.