Showing papers by "L. E. Cross published in 2000"
TL;DR: High resolution x-ray powder diffraction measurements on poled PbZr1-xTixO3 (PZT) ceramic samples have shown that for both rhombohedral and tetragonal compositions the piezoelectric elongation of the unit cell does not occur along the polar directions but along those directions associated with the monoclinic distortion.
Abstract: High resolution x-ray powder diffraction measurements on poled PbZr1-xTixO3 (PZT) ceramic samples close to the rhombohedral-tetragonal phase boundary (the so-called morphotropic phase boundary) have shown that for both rhombohedral and tetragonal compositions the piezoelectric elongation of the unit cell does not occur along the polar directions but along those directions associated with the monoclinic distortion. This work provides the first direct evidence for the origin of the very high piezoelectricity in PZT.
921 citations
TL;DR: In this article, three sets of oxygen vacancies related dielectric peaks (peaks A, B, and C) were measured from 10 to 800 K. The results show that the Maxwell-Wagner polarization is not the main mechanism, and the Skanavi's model also cannot be directly applied.
Abstract: The temperature dependence of dielectric properties and electrical conduction of $({\mathrm{Sr}}_{1\ensuremath{-}1.5x}{\mathrm{Bi}}_{x}){\mathrm{TiO}}_{3} (0.0133l~xl~0.133)$ was measured from 10 to 800 K. Three sets of oxygen vacancies related dielectric peaks (peaks A, B, and $C)$ were observed. These peaks could be greatly suppressed or eliminated by annealing the samples in an oxidizing atmosphere, and enhanced or recreated by annealing in a reducing atmosphere. The results show that the Maxwell-Wagner polarization is not the main mechanism, and the Skanavi's model also cannot be directly applied. A tentative explanation was suggested. Peak A, observed in the temperature range of 100--350 K with the activation energy for dielectric relaxation ${E}_{\mathrm{relaxA}}=0.32--0.49$ eV, is attributed to the coupling effect of the conduction electrons with the motion of the off-centered Bi and Ti ions; the conduction carriers in this temperature range are from the first ionization of oxygen vacancies ${(V}_{o}).$ Peaks B and C are also discussed.
855 citations
TL;DR: In this paper, a detailed analysis of the detailed structure of the tetragonal and monoclinic PZT phases on a sample with $x=0.45--0.48$ for which the lattice parameters are, respectively,
Abstract: The perovskitelike ferroelectric system ${\mathrm{PbZr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ (PZT) has a nearly vertical morphotropic phase boundary (MPB) around $x=0.45--0.50.$ Recent synchrotron x-ray powder diffraction measurements by Noheda et al. [Appl. Phys. Lett. 74, 2059 (1999)] have revealed a monoclinic phase between the previously established tetragonal and rhombohedral regions. In the present work we describe a Rietveld analysis of the detailed structure of the tetragonal and monoclinic PZT phases on a sample with $x=0.48$ for which the lattice parameters are, respectively, ${a}_{t}=4.044$ \AA{}, ${c}_{t}=4.138$ \AA{}, at 325 K, and ${a}_{m}=5.721$ \AA{}, ${b}_{m}=5.708$ \AA{}, ${c}_{m}=4.138$ \AA{}, $\ensuremath{\beta}=90.496\ifmmode^\circ\else\textdegree\fi{},$ at 20 K. In the tetragonal phase the shifts of the atoms along the polar [001] direction are similar to those in ${\mathrm{PbTiO}}_{3}$ but the refinement indicates that there are, in addition, local disordered shifts of the Pb atoms of $\ensuremath{\sim}0.2$ \AA{} perpendicular to the polar axis. The monoclinic structure can be viewed as a condensation along one of the $〈110〉$ directions of the local displacements present in the tetragonal phase. It equally well corresponds to a freezing-out of the local displacements along one of the $〈100〉$ directions recently reported by Corker et al. [J. Phys.: Condens. Matter 10, 6251 (1998)] for rhombohedral PZT. The monoclinic structure therefore provides a microscopic picture of the MPB region in which one of the ``locally'' monoclinic phases in the ``average'' rhombohedral or tetragonal structures freezes out, and thus represents a bridge between these two phases.
738 citations
TL;DR: In this article, the stability region of all three phases has been established from high-resolution synchrotron x-ray powder-diffraction measurements on a series of highly homogeneous samples with $0.42l~xl~0.52.$ at 20 K.
Abstract: Recent structural studies of ferroelectric ${\mathrm{PbZr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ (PZT) with $x=0.48,$ have revealed a monoclinic phase in the vicinity of the morphotropic phase boundary (MPB), previously regarded as the boundary separating the rhombohedral and tetragonal regions of the PZT phase diagram. In the present paper, the stability region of all three phases has been established from high-resolution synchrotron x-ray powder-diffraction measurements on a series of highly homogeneous samples with $0.42l~xl~0.52.$ At 20 K, the monoclinic phase is stable in the range $0.46l~xl~0.51,$ and this range narrows as the temperature is increased. A first-order phase transition from tetragonal to rhombohedral symmetry is observed only for $x=0.45.$ The MPB, therefore, corresponds not to the tetragonal-rhombohedral phase boundary, but instead to the boundary between the tetragonal and monoclinic phases for $0.46l~xl~0.51.$ This result provides important insight into the close relationship between the monoclinic phase and the striking piezoelectric properties of PZT; in particular, investigations of poled samples have shown that the monoclinic distortion is the origin of the unusually high piezoelectric response of PZT.
501 citations
TL;DR: In this paper, the dielectric constants of 1-μm-thick CaTiO3 films are very close to that observed in the bulk materials, and they can be tuned by electric field by 6% at room temperature and 10% at 200 K.
Abstract: We have deposited CaTiO3 thin films on SrRuO3 electrode layers on SrTiO3 and LaAlO3 substrates by pulsed laser deposition. The low-frequency dielectric properties were measured from 4 to 300 K. We found that the dielectric constants of 1-μm-thick CaTiO3 films are very close to that observed in the bulk materials. The dielectric loss depends on the temperature and is on the order of 10−4 at low temperature. The dielectric constants of the films can be tuned by electric field by 6% at room temperature and 10% at 200 K.
64 citations
TL;DR: In this article, the direct-current (dc) electric field dependence of dielectric constant around paraelectric-ferroelectric transition in Cd2Nb2O7 has been studied.
Abstract: The direct-current (dc) electric-field dependence of dielectric constant around paraelectric–ferroelectric transition in Cd2Nb2O7 has been studied The results show significant suppression of the dielectric constant by the application of dc bias The electric-field dependence of the dielectric constant at the temperature around paraelectric–ferroelectric phase transition can be well described by the modified Devenshire relation including a cluster term, ie, e(E)=e1−e2E2+e3E4+(Px/e0)[cosh(Ex)]−2 The fit parameters indicate that the polar-cluster carries polarization P=∼05–25 mC/m2 with the cluster size of L=∼11–15 nm
39 citations
TL;DR: The physical nature of the dielectric anomalies around 18 and 30 K has been the focus of the study, and a possible explanation is given in this article, where the authors propose a possible mechanism for the anomalous behavior of Bi:SrTiO 3.
39 citations
TL;DR: In this article, the dielectric behavior of SrTiO3 single crystals under high dc electric field (up to 50 kV/cm) was reported, and the rounding dielectrics constant peaks were induced by the application of dc bias.
Abstract: The dielectric behavior of SrTiO3 single crystals under high dc electric field (up to 50 kV/cm) is reported in this letter. The rounded dielectric constant peaks are induced by the application of dc bias, and the corresponding dielectric losses are observed. The results show that dielectric loss under dc bias consists of several components coming from “defects mode” and “induced mode.” The field dependence of these modes is studied and their physical nature is discussed.
38 citations
TL;DR: In this article, the authors used the Cole-Cole equation fitting of the frequency dependence of dielectric constant and loss to obtain more precise relaxation time data, compared to the data reported in the literature.
Abstract: This article reports a study on the dielectric relaxation processes of Cd2Nb2O7 compound. Three dielectric relaxation modes I, II, and III were reexamined. By using the Cole–Cole equation fitting of the frequency dependence of dielectric constant and loss, we obtained more precise relaxation time data, compared to the data reported in the literature. The results indicate that the relaxation time for mode I follows the Arrhenius law with one slope rather than two slopes as reported in the literature in the frequency range of 102–105 Hz. However, the parameters obtained from the Arrhenius law fit are not physically reasonable. More physically reasonable parameters can be obtained by fitting the relaxation time to the empirical Vogel [Z. Phys. 22, 645 (1921)]–Fulcher [J. Am. Ceram. Soc. 8, 339 (1925)] relation with essentially the same fitting quality. A comparison of Cd2Nb2O7 with well known triglycine sulphate (TGS) is made. The similarity between the dielectric response of Cd2Nb2O7 and TGS is emphasized. ...
33 citations
TL;DR: In this article, the effect of dc electric field and post-treatment on the dielectric properties of SrTiO3 single crystals is reported. And the possible physical mechanism is briefly discussed.
Abstract: The effect of dc electric field and post-treatment on the dielectric properties of SrTiO3 single crystals are reported. Both the dielectric constant and the loss tan δ decrease after post-treatment in flowing oxygen environment for 26 h at 1100 °C. The possible physical mechanism is briefly discussed. The dielectric behavior under dc electric field is measured. The rounded dielectric constant peak is induced by application of dc bias, and the corresponding dielectric loss is presented, which show more complicated behavior and usually are missing in the literature. In this work, it is found that the temperature (Tm) of the dielectric constant maximum shifts to higher temperatures with increasing dc electric field E, and follows the Tm∼E2/3 relation, indicating an induced ferroelectric-like behavior with the second-order phase transition under dc bias.
29 citations
TL;DR: In this article, the composition-dependent electrical properties in (Pb,La, Zr,Ti,Sn)O3 antiferroelectric-ferroelectric phase switching thin and thick films have been systematically studied and compared with bulk ceramics.
Abstract: The composition-dependent electrical properties in (Pb,La)(Zr,Ti,Sn)O3 antiferroelectric-ferroelectric phase switching thin and thick films have been systematically studied and compared with bulk ceramics. The films were deposited on Pt-buffered silicon substrates by a sol-gel method. The results show that the dependence of low-field dielectric properties on compositions in the films is similar to that in bulk ceramics but the variation of high field properties (polarization or hysteresis loops) is quite different, which may be attributed to the special mechanical boundary condition of the films. While all the films with compositions in the antiferroelectric tetragonal region in the phase diagram demonstrate the existence of remanent polarization in the hysteresis loops, the films with zero remanent polarization can be obtained in the antiferroelectric orthorhombic region. This is because the films are under high tensile stress due to the thermal mismatch between the film and substrate, which tends to stabilize the ferroelectric phase and causes the retention of ferroelectric phase for the films in the antiferroelectric tetragonal region because of their relatively small free energy difference between the antiferroelectric phase and ferroelectric phase.
TL;DR: In this paper, a 10-μm-thick single-crystal films have been fabricated by adjusting the stress level in the implantation damage layer to induce room-temperature etchless exfoliation.
Abstract: We report on the implementation of crystal ion slicing in potassium tantalate (KTaO3). Deep-ion implantation is used to create a buried sacrificial layer in (001) single-crystal wafers of KTaO3. 10-μm-thick single-crystal films have been fabricated by adjusting the stress level in the implantation damage layer to induce room-temperature etchless exfoliation. Crack propagation is found to depend critically on implantation dose, with a threshold dose for exfoliation near 1×1016 cm−2. A significant implantation-induced etch selectivity between the sacrificial layer and the rest of the sample is also found. Capacitance measurements show that the films exhibit a bulk-like dielectric constant and loss tangents below 0.01 at low temperatures.
TL;DR: In this article, the electron-irradiation induced ferroelectric-to-relaxor phase transition in poly (vinylidene fluoride-trifluoroethylene) (P(VDF/TrFE)) copolymer was investigated.
Abstract: The electron-irradiation induced ferroelectric-to-relaxor phase transition in poly (vinylidene fluoride-trifluoroethylene) (P(VDF/TrFE)) copolymer was investigated. One polymer with a composition of 53 mol% VF2 (PVDF53) and a Curie temperature of 67°C, and another with 76 mol% VF2 (PVDF76) and a Curie temperature of 136°C, were used in the research. Changes in hysteresis loop, permittivity and electrostriction during the phase transition were measured. X-ray diffraction showed that PVDF53 had a second-order phase transition during the irradiation in which the structure was changing continuously, while PVDF76 had a first-order phase transition in which the structure changed discontinuously. Field-induced piezoelectric response was measured using a loudspeaker which provided a vibrational force, and d31 = 135 pC/N at bias E3 = 40 MV/m was obtained. The conditions for electron irradiation and composition of the copolymers were discussed.
TL;DR: In this paper, a Flextensional actuator was designed using commercial multilayer stacked actuator so as to produce large displacements at intermediate force levels, which eliminated the need for bonding the actuators into the frame and permitted easy series connection of multiple units.
Abstract: A flextensional actuator was designed using commercial multilayer stacked actuator so as to produce large displacements at intermediate force levels. The simple design chosen eliminated the need for bonding the actuators into the frame and permitted easy series connection of multiple units. To satisfy the need for a fiber grating tuning device to interrogate an array of Bragg grating fiber optic stress sensors, a tuning device using four series connected units was constructed. The unit performs well, but the actual measured amplification is less than theoretical expectation. The problem was traced to unwanted flexing of the simple original frame and a hinged more robust flexing beam construction was shown to eliminate the problem.
TL;DR: In this paper, the dielectric and pyroelectric properties of crystal ion slicing (CIS) LiNbO3 films were investigated in order to evaluate the ferroelectric property of the films compared to the parent bulk single crystals.
Abstract: 10 μm thick LiNbO3 crystal films have been fabricated from a poled bulk single crystal by the technique of Crystal Ion Slicing (CIS). The CIS technique is a promising approach to fabricate the free standing ferroelectric films for various integration applications and thin film structures. In this paper, the dielectric and pyroelectric properties of CIS LiNbO3 films as well as their temperature dependence were investigated in order to evaluate the ferroelectric properties of the films compared to the parent bulk single crystals. The investigation of the dielectric and pyroelectric responses were carried out in the temperature range of 30-100°C. The results suggest that the film retains the ferroelectric properties of the bulk crystal with magnitudes close to those of single crystal values at room temperature. However, the virgin CIS film showed an additional distinct phase transition in the temperature range around 75°C, as determined from the dielectric and pyroelectric responses. This phase tran...
21 Jul 2000
TL;DR: In this paper, the design of advanced micromachined ferroelectric ultrasound transducers for use at 3 MHz was discussed, with sol-gel PZT as the active ferro-electric layer deposited on insulating layers of ZrO/sub 2/ and SiO/ sub 2/ layers.
Abstract: This paper discusses the design of advanced micromachined ferroelectric ultrasound transducers for use at 3 MHz. 16/spl times/16 arrays of resonant monomorph sensors have been constructed, with sol-gel PZT as the active ferroelectric layer deposited on insulating layers of ZrO/sub 2/ and SiO/sub 2/. A novel in-plane polarization of the PZT is used to maximize sensitivity, while trading off reduced output capacitance to match the CMOS buffer electronics. This results in about 30 dB improved sensitivity compared to conventional polarizing across the thickness of the PZT layer. An equivalent circuit model as well as Finite Element results are presented. Test results are reported including transmit response, receive sensitivity.
04 Jun 2000