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Electromechanical properties of 0.5Pb(Ni1/3Nb2/3)O3-0.5Pb(Zr0.7Ti0.3)O3 (0.5PNN-0.5PZT(0.7/0.3)) ceramics near a morphotropic phase boundary were investigated under the hydrostatic pressure p up to 600 MPa at room temperature, where the piezoelectric constants d33 = 850 pC/N and d31 = 332 pC/N were obtained in this material. The remarkable change in the pressure dependence of the electromechanical response was found, where the resonance and antiresonance curves in impedance and phase in k31 mode for the transverse electromechanical property of 0.5PNN-0.5PZT(0.7/0.3) decrease with increasing pressure, and disappear completely at about p = 600 MPa. It was also confirmed that after removal of applied pressures, the electromechanical response recovers. Accompanied with such suppression of piezoelectric response, the increase in 30% of the permittivity ϵr with increasing p, was observed.

Dielectric properties of the solid solution system (1-x)Pb(Mg 1/3 Nb 2/3 )O 3 −xPbZrO 3 (0 < x < 1) have been studied under hydrostatic pressures up to 0.6 GPa. For the concentration of x ≤ 0.7, the values of the dielectric maximum and the temperature of the dielectric maximum decreased with increasing pressure. For x = 0.9, phase transition from ferroelectric phase to antiferroelectric phase occurs at 0.4 GPa with increasing pressure. For x = 0.95, the dielectric maximum and the peak temperature decreased up to 0.2 GPa, and above 0.2 GPa the peak temperature increased. Pressure-temperature-concentration phase diagram in (1-x)PMN-xPZ was determined by means of dielectric properties and hysteresis loop observation.

The piezoelectric properties of PMN-PT ceramics with compositions near a morphotropic phase boundary were investigated under pressures p upto 150 MPa. The resonance and antiresonance frequency characteristics of impedance and phase in the k 31 mode in the tetragonal phase for PMNT (67/33) and in the rhombohedral one for PMNT (69/31) ceramics were observed under various pressures. The resonance frequency f r remains almost constant and antiresonance one f a tends to increase with increasing p. The electromechanical coupling coefficient k 31 in the k 31 mode increases and the electromechanical quality factor Q decreases with increasing p. The decrease in Q with p is due to ferroelectric domain wall motions. The relative permittivity ϵ r increases with increasing p. Such an increase in both k and ϵ r dependent on p seems to be related to the decrease in ferroelectric domain size.

The piezoelectric and dielectric properties of Pb(Mg1=3Nb2=3)O3–PbTiO3 (PMNT) ceramics with compositions near a morphotropic phase boundary (MPB) were investigated under pressures p up to 700 MPa at 25 � C. The resonance and antiresonance frequency characteristics of impedance and phase in the k31 mode for PMNT (67/33) and (69/31) ceramics were observed under various pressures. The effect of pressure on their responses were clearly observed. The electromechanical coupling coefficient k31 in the k31 mode increases and the electromechanical quality factor Q decreases with increasing p at pressures lower than 100 MPa. The decrease in Q with p is due to the scattering of ultrasonic waves from the domain boundary. The relative permittivity "r increases with increasing p. Such increases in both k and "r with p seem to be related to the increase in topographical domain-wall density associated with monoclinic distortions. At pressures higher than 100 MPa, their electromechanical suppression in PMNT ceramics occurs at each pressure, corresponding to the electromechanical coupling coefficient k. "r increases with pressure-induced electromechanical suppression. The change in "r with such suppression corresponds to k. Such a phenomenon seems to be due to the increase in piezoelectric load based on the increase in complex domain wall density coming from the increase in free energy with pressure. [DOI: 10.1143/JJAP.47.7650]

In this work, in order to investigate the dielectric properties related to the domain structure in PMN-PT solid solutions, simultaneous optical and dielectric measurements were made.

The annealing effect of the phase transition in PbIn½Nb½O3 (PIN) crystal was investigated by means of the dielectric constant measurement and the polarizing microscopic observation. Using one and the same sample plate of the PIN, it was observed that the antiferroelectric transition gradually changes into the diffuse phase transition as the annealing temperature increases. On the basis of the observation by an optical microscope, the annealing effect of the diffuse phase transition in the relaxor was discussed.

In this present study, we have investigated the dielectric behavior of CaCu3Ti4O12, SrCu3Ti4O12 (SCTO), BaCu3Ti4O12 (BCTO), and the pressure and thickness effects of the dielectric property in CCTO.

Domain observation in Pb(In1/2Nb1/2)O3–PbTiO3[PIN-PT] solid-solution single crystals near the morphotropic phase boundary (MPB) was carried out by polarized light microscopy. The rhombohedral (R)-to-tetragonal (T) phase transition began to take place abruptly in the (110) plane at about 6 kV/cm in the rhombohedral (001) 0.72PIN-0.28PT plate with the dc electric field applied along the direction. The phase boundary between the R and T phases along the (110) plane approached the R region at the expense of the R region, and the R and T phases coexisted in a wide dc field range from 6 kV/cm to 12 kV/cm. The electric-field-induced R-to-T phase transition was very diffuse. The (110) plane plays an important role in this phase transition. The effects of the dc electric field on the domain configuration and permittivity of the rhombohedral (110) 0.69PIN-0.31PT plate were simultaneously investigated, and the contributions of the 109° and 71° polarization configurations to permittivity were discussed on the basis of the Ishibashi theory.

For lead indium niobate lead titanate(PIN-PT) binary system near the morphotropic phase boundary(MPB) composition with a high Curie Temperature Tc>250 °C, the temperature (30-380 °C), compositions (0.28,0.37,0.38,0.54), and orientation ([100], [111]) dependences of permittivity, dielectric loss tangent, spontaneous polarization, and coercive field were investigated. The poling effect on the permittivity was presented. The electromechanical coupling coefficient in rectangular bar mode, k 33 '=70%, along the [100] axis in the tetragonal 0.62PIN-0.38PT was estimated at 30 °C.

Single crystals and ceramics of (1- x )PMN– x PT were synthesized in the whole concentration range from x =0 to x =1, and the temperature-concentration phase diagram of the system was determined fr...

PbIn 1/2 Nb 1/2 O 3 (PIN) single crystal plates obtained by different thermal treatment were investigated by means of polarizing microscopic observations. It was found that, in an as-grown PIN (cal...

The single crystals of Pb(In1/2Nb1/2)O3(PIN)-PbTiO3(PT) solid solution near morphotropic phase boundary(MPB) were flux-grown from PbO-In2O3-Nb2O5-Ti2O3 system using the PbO-B2O3-PbF2 flux. The X-ray studies confirmed that O.67PIN-O.33PT has the rhombohedral structure at room temperature. The temperature, dc-bias field E and pressure p dependences of dielectric properties of PIN-PT single crystals were investigated. The permittivity e has a peak at the Curie point Tc and then a shoulder at the phase transition temperature T1 below Tc with cooling, corresponding to the sequence of transitions of cubic-tetragonal-rhombohedral phases. The value of the spontaneous polarization along the [100] direction in (1-x)PIN-xPT with x=0.33 is about 42 μ C/cm2 at room temperature. The E-T and p-T phase diagrams for (1-x)PIN-xPT single crystals near MPB were determined dielectrically.

The dielectric properties of Pb(In 1/2 Nb 1/2 )O 3 (abbreviated as PIN) single crystal were investigated under hydrostatic pressures up to 0.7 GPa. The ordered PIN was confirmed to be antiferroelectric by observation of clear P - E double hysteresis loops below the transition temperature. There is a striking pressure effect in the disordered PIN. The relaxor behavior becomes less notable with increasing pressure and disappears at 0.4 GPa. At pressures above 0.4 GPa, the normal phase transition without dielectric dispersion in the low frequency range takes place and with increasing pressure, the temperature T m , indicating the maximum of the dielectric constant, e rm ′ , increases at a rate of 150 K/GPa and the e rm ′ decreases. Such dielectric phenomena with pressure are similar to those observed in antiferroelectric PbZrO 3 .

The voltage drops on the surfaces in PZN–20% PT and PZN–30% PT were investigated using the electrostatic force microscopy (EFM). It was found that the voltage drop per unit length in the a -domain is larger than the one in the c -domains on the sample surface with the ferroelastic domain wall structure, implying that the dielectric constant perpendicular to the spontaneous polarization is larger than the one parallel to the spontaneous polarization in the vicinity of the morphotropic phase boundary (MPB). Dielectric anisotropy in the vicinity of the MPB was discussed.

The dielectric properties of ferroelectric (CH 3 ) 2 NH 2 Al(SO 4 ) 2 ·6H 2 O (DMAAS) crystal under pressures have been investigated. The ferroelectric phase transition temperature T c decreases rapidly with increasing pressure with d T c d p =-10.2° C/kbar at pressures below 0.8 kbar. At pressures above this, the pressure-induced new phases I and II appear. The pressure-temperature phase diagram of DMAAS in the temperature and pressure region 0 to - 170°C and 0–1.6 kbar was dielectrically determined.

The dc-electric field dependence of the dielectric properties (complex permittivity and relaxation time) of the antiferroelectric betaine phosphate was investigated under various frequencies. The strong dielectric dispersion along the b-axis associated with the field-enforced ferroelectric phase transition was observed. The slowing-down of the relaxation time toward a critical electric field Ecr, which induces the forced transition to the ferroelectric phase, was observed. The frequency dependence of the complex relative permittivity obeys the Cole-Cole are law. The relaxation time is of the order of 10−5s near Ecr.

A new perovskite Pb(In1/2Ta1/2)O3 compound was successfully prepared through the wolframite phase oxide, utilizing, fast firing. Its x-ray powder patterns show cubic patterns (a=4. 109A) at room temperature. Dielectric properties of Pb(In1/2Ta1/2)O3 is found to be typical of a ferroelectric relaxor exhibiting a broad maximum of the permittivity at 5°C at 1kHz, strong dielectric dispersion around room temperature and rounded polarization-electric field hysteresis loops.

The dc-electric field dependence of the dielectric properties(complex permittivity and relaxation time) of the antiferroelectric cupric formate tetrahydrate was investigated under various frequencies. The strong dielectric dispersion along the b axis associated with the field-enforced ferroelectric phase transition was observed. The slowing down of the relaxation time toward a critical electric field Ecr, which induces the forced transition to the ferroelectric phase, was observed. The frequency dependence of the complex relative permittivity obeys the Cole-Cole arc law. With increasing Ed, the dielectric dispersion strength increases gradually, rapidly near Ecr in the antiferroelectric phase and then decreases monotonically in the ferroelectric one. The relaxation time is of the order of 10−4s near Ecr.

The pressure (0–6kbar), DC-bias field(0–11kV/cm) and frequency(300Hz–100kHz) dependence of dielectric properties of PIN ceramics prepared by different thermal processing techniques (conventional method:sample A and fast firing;sample B) were reported. PIN sample A reveals coexistence of a ferroelectric relaxor (disordered state) and an antiferroelectric phase(ordered one), while sample B reveals a ferroelectric relaxor. For sample A, the permittivity maximum(erm′ =1800 at 1kHz) temperature Tm decreases with pressure(dTm/dp=−2°C/kbar) and antiferroelectric transition temperature Tt increases with p(dTt/dp=5°C/kbar). For sample B(with e rm′ = 3500 at 1kHz), the Tm decreases with dTm/dp=−3°C/kbar, and a remarkable decrease in e rm′ with DC-bias field and a strong dielectric relaxation of polydispersive type which obeys the Cole-Cole arc law were observed.

Phase transitions and dielectric properties of (1−x)Pb(In1/2Nb1/2)O3(PIN)‐xPbZrO3(PZ) solid solution system have been examined as a function of the concentration x. Two morphotropic phase boundaries were identified: (1) pseudocubic to rhombohedral phase boundary at x=0.35 and (2) rhombohedral to orthorhombic at x=0.8. For x

The frequency dependence of the complex permittivity of the antiferroelectric betaine phosphate was investigated under various dc electric fields. The strong dielectric relaxation along the b -axis associated with the field-enforced ferroelectric phase transition was observed. The slowing down of the relaxation time toward a critical electric field E cr , which induces the forced transition to the ferroelectric phase, was observed.

Dielectric properties such as the permittivity, dielectric loss tangent and spontaneous polarization of highly ordered perovskite Pb(Yb1/2Ta1/2)O3 (PYT) compound which were prepared through the wolframite phase oxide were investigated. A dielectric anomaly which is characterized by a slight dielectric dispersion was found at a temperature Tm (e.g., Tm; 177 and 183 °C at 1 and 100 kHz, respectively). At temperatures below Tm, polarization P‐electric field E hysteresis loops were observed, and then ferroelectricity in antiferroelectric ordered perovskite PYT was confirmed. Highly ordered PYT has two successive paraelectric‐antiferroelectric‐ferroelectric phase transitions, similar to highly ordered perovskite lead cobalt tungstate (PCW).

A new perovskite Pb(In1/2Ta1/2)O3 compound was successfully prepared through the wolframite phase oxide, utilizing fast firing for the enhancement of formation of the perovskite phase and densification. Dielectric properties of Pb(In1/2Ta1/2)O3 are found to be typical of a ferroelectric relaxor exhibiting a broad maximum of the permittivity at 5 °C at 1 kHz, strong dielectric dispersion around room temperature, and rounded polarization‐electric field hysteresis loops.

The dielectric properties in 0.47Pb(Yb1/2Nb1/2)O3–0.53PbTiO3 (0.47PYN–0.53PT) single crystals near the morphotropic phase boundary (MPB) were investigated in the frequency range from 10 kHz to 1 MHz. Remarkable dielectric relaxation was observed along the polar 〈001〉 direction in the tetragonal 0.47PYN–0.53PT single crystal near the MPB. An increase of the dielectric relaxation time was observed as the Curie temperature was approached. The real part and the imaginary part of the complex relative permittivity obeys the Cole–Cole arc law, and the Debye type dielectric dispersion with the polydispersive type among the order-disorder type ferroelectrics was observed.

The temperature dependence of the complex relative permittivity in a relaxor ferroelectric solid solution 24Pb(In1/2Nb1/2)O3–46Pb(Mg1/3Nb2/3)O3–30PbTiO3 (PIN–PMN–PT) crystal poled and depoled was measured from room temperature to 200 °C at various frequencies. The poled sample exhibits transitions from the ferroelectric (FE) phase to the relaxor (RE) phase on heating, and after that, the depoled one exhibits those from the RE phase to the glassy freezing phase on cooling. An RE-type dielectric dispersion with a weak frequency (f) dependence was observed. Such a dielectric dispersion in the RE state was found to be based on tweed domain structures observed by polarization light microscopy (PLM) and piezoelectric force microscopy (PFM) due to the competition between the antiferroelectric (AFE) and FE coupling in the RE state. The temperature dependence of complex permittivity with resonance- and relaxor-type dielectric dispersions in the poled and depoled samples was characterized by hierarchical domain structures.

The strong dielectric dispersion along the b‐axis associated with the field‐enforced ferroelectric phase transition was observed. The slowing down of the relaxation time toward a critical electric field Ecr was observed. The frequency dependence of the complex permittivity obeys the Cole‐Cole arc law. With increasing dc‐electric fields, the dielectric dispersion strength increases gradually, rapidly near Ecr in the antiferroelectric phase and then decreases in the ferroelectric one.

The electromechanical and dielectric responses in transverse and longitudinal modes for relaxor ferroelectric solid solution Pb(Mg1∕3Nb2∕3)O3–PbTiO3 (PMNT) near a morphotropic phase boundary composition were investigated under hydrostatic pressures up to 700MPa at 25°C. The effect of pressure on their responses remarkably appeared. Their electromechanical suppression in PMNT single crystal and ceramics occurs at each pressure, corresponding to electromechanical coupling coefficient k. The permittivity e increased with pressure-induced electromechanical suppression. The change in e with such suppression corresponds to k. Such phenomena were considered to be due to the increase in piezoelectric load based on decrease of domain size coming from increase in free energy with pressures.

Dielectric properties of (1-x)Pb(Sc1/2Ta1/2)O3(PST)–xPbZrO3 (PZ) (00.7, the permittivity ε r ′ exhibits a peak at the phase transition temperature T c. With increasing x, the peak value decreased and T t shifted towards the higher temperature region. The phase below T c was confirmed to be ferroelectric by observation of P-E hysteresis loops. Phase transformation from the relaxor to the ferroelectric state occurred at x=0.7. For x>0.8, a steplike anomaly appeared at T t below T c. With increasing x, T t shifted towards the higher temperature region. There was a structural change characterized by the splitting of the structure-sensitive maximum of the (200) reflection of XRD patterns, similar to orthorhombic PZ, around x=0.8. Two morphotropic phase boundaries were found: one between the pseudocubic and rhombohedral phases with ε rm ′ of 15000 at 100 kHz was at x=0.7, and the other between the rhombohedral and orthorhombic phases was at x=0.8.

In Ba(Ti1- x Sn x )O3 solid solution, for Sn concentration x≤0.1, the permittivity follows the Curie-Weiss law above the Curie point T c. The increase in the peak value of the permittivity at T c is due to the change in ferroelectric transition from first order to second order with increasing x. For x>0.1, some deviations from the Curie-Weiss law are observed in a narrow temperature region above T c. The diffuse phase transition was observed. For x>0.2, the Curie-Weiss law does not hold over a wide temperature range. The dielectric dispersion was observed in the radio-frequency range (10 kHz–10 MHz). With increasing Sn concentration, the change in the phase transition from a normal ferroelectric transition to relaxor through the diffuse phase transition was observed.

Lead based-complex perovskite solid solutions Pb(In(1-x)/2Yb x/2Nb1/2)O3 were prepared through wolframite phase oxides (InNbO4 and YbNbO4), and their dielectric properties were investigated. For Yb concentrations xx, the maximum permittivity increases. For x>0.20, in addition to the dielectric dispersion, a new frequency-independent dielectric anomaly appears at temperature T t. With increasing x, T t increases rapidly and the dielectric dispersion decreases. There is a structural change which is characterized by the splitting of the structure-sensitive maximum of the (200) reflection of X-ray diffraction (XRD) patterns around x=0.20. Thus, the morphotropic phase boundary exists at around x=0.20.

Perovskite Pb(In1/2Nb1/2)O3 and Pb(In1/2Ta1/2)O3 compounds were successfully prepared with the aid of wolframite phase oxide, utilizing a fast firing technique. Dielectric properties of Pb(In1/2Nb1/2)O3 and Pb(In1/2Ta1/2)O3 compounds prepared by such a technique were found to be typical of ferroelectric relaxors exhibiting a broad maximum of permittivity and a strong dielectric dispersion.

A large dielectric dispersion in ordered perovskite Pb(Yb1/2Nb1/2)O3 has been observed over a wide temperature range of -140 to 190°C in the frequency range of 1 kHz to 4 MHz.

The pressure (0–10 kbar) and temperature (10–130°C) dependence of the dielectric properties of squaric acid (H2C4O4) were investigated. From the large isotope effect on the transition temperature of Tnd/Tn=1.38 (the superscript d stands for deuteration) and the large decrease of Tn with pressure of dTn/dp=-13°C/kbar, the phase transition mechanism for H2C4O4 is discussed microscopically using the tunneling model of the proton on the O–H–O bond accepted for KH2PO4-type crystals. The temperature dependence of the permittivity under constant pressure is interpreted in terms of the antiferroelectric ordering of the proton using the pseudospin model incorporating proton tunneling.

The real and imaginary parts of permittivity of Cu(HCOO)24H2O were measured over a range of pressures up to 20 kbar under various frequencies, and the following remarkable facts were found: (1) the reciprocal real part of permittivity in the paraelectric phase decreases linearly with increasing pressure. (2) the dielectric relaxation is on the Cole-Cole's arc law with β = 0.88 in the paraelectric phase and β = 0.68 in the phase.

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.

The dielectric and pyroelectric properties of (CH3 NH CH2 COOH)3 CaCl2 (1-x) I2x (TSCCI) were measured. TSCCI shows the dielectric hysteresis loop biased largely. Such large internal bias field causes the depression of the permittivity and the reduction of the dielectric loss and will lead to high performance of the pyroelectric detector.

The dielectric properties such as the permittivity epsilon , the dielectric loss tangent and the spontaneous polarisation Ps of iodinated trissarcosine calcium chloride were measured at various pressures up to 9 kbar. The peak of epsilon is depressed and broadened by the large internal bias field Eb. The P-E hysteresis loop is highly biased. With increasing I concentrations x, both the peak value of epsilon and the value of Ps decrease rapidly. The ferroelectric transition temperature Tc(x) decreases with increasing x according to the relation (Tc(x)/Tc(0))2=(1-x/xc) where xc is the critical concentration and is estimated as 0.25. The Tc increases greatly with increasing p while the Ps is almost independent of p. The triple point (paraelectric-ferroelectric-new phase) shifted towards higher pressures and lower temperatures with increasing x. The effect of substitution of I for Cl on the dielectric properties is more remarkable than that of Br for Cl.

Some dielectric properties of Cu(HCOO)24H2O such as the frequency dependence of the complex permittivity, D-E double hysteresis loops and the effect of the d.c. electric biasing field on the Curie point were investigated under hydrostatic pressure. The results are: (1) The dielectric relaxation obeys the Cole-Cole's dispersion law. (2) The D-E double hysteresis loops observed under hydrostatic pressure are as predicted analytically in a previous paper (S. Fujimoto et al.: Japan. J. appl. Phys. 15 (1976) 595). (3) The real part of the permittivity in the antiferroelectric phase increases with increasing d.c. electric biasing field. (4) The Curie point shifts toward the lower temperature side with increasing d.c. electric biasing field.

The pressure (0 to 7 kbar) and temperature (-120 to +80 degrees C) dependence of the dielectric properties for TlH2PO4 and TlD2PO4 were investigated. The large isotope effects on the transition temperature (Tc) and the pressure derivative of Tc were observed. From these facts and the negative pressure coefficient of Tc, the phase transition mechanism for TlH2PO4 is microscopically discussed on the basis of the tunnelling model of the proton on the O-H---O bond. The temperature dependence of the permittivity of TlH2PO4 under constant pressure is interpreted in terms of antiferroelectric ordering of the proton by making use of the pseudospin model. It is suggested from the present dielectric study that the phase transition for TlH2PO4 and TlD2PO4 is not ferroelectric but antiferroelectric.

The real and imaginary parts of complex relative permittivity along the b axis of antiferroelectric Cu(HCOO)24H2O single crystals were measured at 1 kHz over a temperature range −10 to −45 °C under various uniaxial stresses. The antiferroelectric phase transition temperatures (ϑc) under uniaxial stress along the c axis (σ3) and the a′ axis (σ1) vary linearly with the stress coefficients of dϑc/dσ3=3.3×10−8 K/(N/m2) and dϑc/dσ1=2.6×10−8 K/(N/m2), respectively, and these values agree well with the values calculated by the Clausius‐Clapeyron equation. The temperature dependence of the real part of complex permittivity in the paraelectric phase under various uniaxial stresses obeys the Curie‐Weiss law. The characteristic temperatures (ϑ0) under σ3 and σ1 vary linearly with the stress coefficients of dϑ0/dσ3=−6.7×10−7 K/(N/m2) and dϑ0/dσ1=−10.8×10−7 K/(N/m2), respectively. The dielectric properties under uniaxial stresses are elucidated by the phenomenological theory for the antiferroelectrics under uniaxial s...

The dependence of the dielectric properties (permittivity and phase transition temperatures) on the DC bias field (0-0.9 MV m-1) for the paraelectric to ferroelectric (I to II) and the paraelectric to pressure-induced phase (I to III) transitions for trissarcosine calcium chloride (TSCC), was measured. The effect of the DC bias field on the dielectric properties is striking for the I to II transition, whereas it is less so for the I to III transition. The above facts support the theory that the pressure-induced phase III is antiferroelectric. The effect of the DC bias field on the dielectric properties for the I to II transition is explained in terms of the phenomenological theory.

Temperature T (30-150°C) and pressure p (0-6 kbar) dependence of the permittivity e and the spontaneous polarization Ps of PbFe1/2Nb1/2O3 ceramics prepared by the use of alkoxides are presented. The e has a broad maximum at the transition point Tt. The value of the exponent for the logarithmic plots of the reciprocal e versus the reduced temperature above Tt is 2.0, which is almost independent of p. As p increases, the Tt decreases with dTtldp = -3.7K/kbar and the maximum value of e decreases. The T and p dependence of e and Ps are explained by a phenomenological theory.

Ordered and disordered ferroelectric transition temperatures of Pb(Sc 1 2 Nb 1 2 )O3 decrease with pressure coefficients o f -4.3 K/kbar and -4.5 K/kbar, respectively, with increasing pressure. For ordered PSN, there is a small decrease in the permitivity e with p, while for disordered PSN, there are both a large decrease in e and an increase in the broadening of the shape of the e maximum with p.

Polarization versus electric field double hysteresis loops along the b -axis of TID 2 PO 4 were observed. From this fact and the permittivity versus temperature characteristic, the low temperature phase of TID 2 PO 4 was confirmed to be antiferroelectric.

For ceramic Pb ( Co 1 2 W 1 2 ) O 3 a remarkable difference in the pressure-temperature phase diagram between increasing and decreasing temperature was found. The intermediate phase II becomes more stable with increasing pressure on cooling than on heating.

For ceramic Pb(Fe 1 2 Nb 1 2 )O 3 , the permittivity ϵ has a broad maximum at the ferroelectric transition temperature Tt. The value of the exponent for the logarithmic plots of the reciprocal ϵ versus reduced temperature above Tt is 2.0 and is almost independent of pressure p. With increasing p, Tt decreases with dTt/dp=-3.7 K/kbar and the maximum value of ϵ decreases.

The dielectric properties of cholesteryl 2, 2, 3, 3-tetrafluoropropionate were measured under hydrostatic pressures of up to 5 kbar. The reciprocal permittivity ε -1 was found to vary almost linearly with temperature T in the normal phase I under a pressure p, and the peak value of ε at the I-II (normal-incommensurate) phase transition temperature T I-II increased with increasing p in the low-pressure region below 3 kbar and tended to saturate in the high-pressure region above 3 kbar. The slope of T I-II against p was 6°C/kbar in the low-pressure region and decreased in the high-pressure region. The dielectric relaxation curves in phase II shifted towards higher temperatures with p, while the relaxation frequency decreased with p at constant temperature. The relaxation curves converged at the II-III (incommensurate-incommensurate) phase transition temperature T II-III with decreasing frequency under pressure. The pressure dependence of activation parameters such as the enthalpy, entropy and volume was also estimated. The slope of T II-III against p was 1.6°C/kbar in the low-pressure region and increased in the high-pressure region. The region of phase II was found to be extended in the low-pressure region and narrowed in the high-pressure region by the application of pressure.

The pressure (0–6 kbar), temperature (-200∼-70°C) and dc bias field (0–9×105V/m) dependence of the dielectric properties (permittivity, spontaneous polarization, coercive field and phase transition temperatures) of trissarcosine calcium chloride (TSCC) were measured. The effect of pressure on the dielectric properties was remarkable. A remarkable decrease in the permittivity occurred at a pressure of about 5 kbar, where the ferroelectric state terminates. The new phase III appeared when pressure was applied and became more stable with increasing pressure. Judging from the dc bias field and temperature dependence of the permittivity and the non-occurrence of hysteresis loops and other considerations, the pressure-induced phase III is believed to be antiferroelectric. The dielectric properties associated with the paraelectric-ferroelectric transition in TSCC are also successfully interpreted in terms of a phenomenological theory.

Anomalous dielectric behaviors in 3M2CPOOB with extremely large spontaneous polarization P s and in 2MBNCBC indicating the reversal of the sign of the P s have been studied under hydrostatic pressure up to 2 kbar. The slope of the pressure-temperature phase diagram was comparable to that of DOBAMBC and other smectic liquid crystals, suggesting that the ferroelectricity is not influenced strongly. Anomalies in both compounds were not influenced by the application of pressures of less than 2 kbar.