Showing papers by "L. E. Cross published in 1985"
TL;DR: In this paper, the PZT rod-polymer composites have been used for low-frequency hydrophone applications and the effect of temperature on the electromechanical properties of the composite has also been investigated.
Abstract: Abstmcr-The objective of the present work was to gain a deeper mensions of the transducer are much smaller than the understanding of the behavior of lead zirconate titanate (PZT) polymer composites for applications such as ultrasonic medical diagnosis in the megahertz frequency range. These composites were originally developed for low-frequency hydrophone applications. The PZT rod-polymer composites have been prepared with five to 30 volume percent PZT using 0.28 mm and 0.45 mm rods. In a disc of PZT rod-polymer composite material, there are three principal types of resonance: the planar mode, the thickness mode, and various lateral modes caused by the regular periodicity of the PZT rod in the composite. These resonance modes have been studied with the following techniques: 1) electrical impedance measurement as a function of frequency and 2) laser probe dilatometry of the dynamic displacement as a function of frequency and position in the composite lattice. The observed resonance behavior is found to be a result of lateral interactions in the composite through the epoxy medium. The effect of temperature on the electromechanical properties of the composite has also been investigated. Implications of these results for optimizing the design of ultrasonic transducers are discussed.
328 citations
TL;DR: In this paper, the electro-acoustic properties of lead zirconate titanate (PZT) rod-polymer composites relevant for ultrasonic transducer applications are reported.
Abstract: Abstmct-The electro-acoustic properties of Lead zirconate titanate (PZT) rod-polymer composites relevant for ultrasonic transducer applications are reported. Acoustic impedance of the composite materials was measured by three different techniques in the frequency range 0.33.5 MHz. Dependence of the acoustic impedance as a function of volume fraction of PZT and frequency was also modeled theoretically. Time-delay spectrometry was employed to calibrate the free-field transmitting and receiving voltage responses of the composite materials. The acoustic impedance of the composite materials was in the range of 3-10 M rayl. The figure of merit in the receiving mode of composite materials was three times that of PZT. The figure of merit for a 20percent PZT composite (2 = 7.3 M rayl) was further enhanced by 50 percent using a single-layer impedance transformer of lucite (2 =3.3 M rayl). These composite materials were molded into curved shapes by simple thermal process to fabricate focused transducers. The axial and lateral beam profiles of focused composite transducers are presented.
131 citations
TL;DR: The ADAGE computer graphics system has been used to develop a modified Devonshire form for the elastic Gibbs function to describe the simple proper ferroelectric phases in the PbZrO3:PbTiO3 family of crystalline solid solutions.
Abstract: The ADAGE computer graphics system has been used to develop a modified Devonshire form for the elastic Gibbs function to describe the simple proper ferroelectric phases in the PbZrO3:PbTiO3 family of crystalline solid solutions The unusual morphotropic phase boundary between tetragonal and rhombohedral forms has been used to help delineate the coefficients in the function at that composition For the Devonshire formulation, spontaneous strain in the ferroelectric phases is assumed to be electrostrictive in origin and an x-ray determination of the strains as function of composition and temperature has been used to derive the composition and temperature dependence of the higher order stiffness coefficients The Gibbs function which has been derived permits for the first time the calculation of the full family of thermal, elastic, dielectric, and piezoelectric parameters for the ferroelectric single domain states and an evaluation of the manner in which these parameters change under different elastic and el
118 citations
TL;DR: In this paper, the dielectric, piezoelectric and pyroelectric properties of fresnoite (Ba2TiSi2Os) single crystal and polar glass-ceramics were studied in the temperature range - 150 to 200°C.
Abstract: The dielectric, piezoelectric and pyroelectric properties of fresnoite (Ba2TiSi2Os) single crystal and polar glass-ceramics were studied in the temperature range - 150 to 200°C. The sign of pyroelectric coefficient is positive at room temperature and becomes negative at 190°C. The dielectric constant, pyroelectric coefficient and planar coupling coefficient show a maximum value at 160°C and the frequency constant shows a minimum at the same temperature. The probable reasons for the anomaly in these properties are discussed.
64 citations
TL;DR: In this article, Li2B4O7 (LTB) was measured in the temperature range from 50°C down through -150°C and showed the pyroelectric figure of merit p/K comparable to the value obtained on TGS at room temperature.
Abstract: Pyroelectric. piezoelectric and dielectric properties of single crystal Li2B4O7 (LTB) are measured in the temperature range from 50°C down through -150°C. At room temperature LTB has dielectric constant K3~10 (at 100 KHz) and dielectric tan δ~1 (10 KHz). At liquid nitrogen temperatures, the tan δ decreased to ~10-3. Pyroelectric coefficient at room temperature measured ~30 µC/m2-K which increased to -120 µC/m2-K at -150°C and showed the pyroelectric figure of merit p/K comparable to the value obtained on TGS at room temperature. Primary and secondary components of pyroelectricity are separated and the results suggest that the major contribution comes from the primary effect in Li2B4O7. Piezoelectric measurements show high values of g33270×10-3 V-m/N and gh100×10-3 V-m/N indicating potential application of Li2B4O7 in the area of pressure sensors.
62 citations
TL;DR: In this article, electric polarizations and elastic strain were measured simultaneously for several lead lanthanum zirconate-titanate (PLZT) compositions cycled around their high-field electric hysteresis loops.
Abstract: Electric polarizations and elastic strain were measured simultaneously for several lead lanthanum zirconate-titanate (PLZT) compositions cycled around their high-field electric hysteresis loops. Using the accepted symbolism for compositions, where the first number gives the mole percent of La2O3 and the second two numbers give the ratio of PbZrO3 to PbTiO3 in the composition, data were taken for (7,7.5,8,8.8,9.5)/65/35 and 8/70/30 compositions. The results show that for all compositions in which the base state is macroscopically nonpolar, the strains are dominantly electro-strictive in nature. Both of the polarization-related constants, Q11 and Q12, are almost independent of temperature and of the same order as in other perovskites but decrease slightly in magnitude with increasing La2O3 content.
39 citations
TL;DR: In this paper, the transmission electron microscope (TEM) was used to directly observe ordered microdomains in Pb(Sc0.5Ta 0.5)O3 (PST).
Abstract: The transmission electron microscope (TEM) was used to directly observe ordered microdomains in Pb(Sc0.5Ta0.5)O3 (PST). The microstructure of both single crystal and polycrystalline PST was studied as a function of S, the degree of order (which was controlled by thermal treatment). The observed domain sizes were in good agreement with the results of prior X-ray studies. It was found that the domain coarsening kinetics are much slower for the single crystal than the polycrystalline material. Also evidence was obtained for the presence of short range order within PST.
27 citations
TL;DR: Polar Sr2TiSi2O8 glass-ceramics were prepared by recrystallizing glasses in a steep temperature gradient and the dielectric, piezoelectric and pyroelectric properties were studied as a function of temperature in the temperature range −150 to 200 ǫ C as mentioned in this paper.
Abstract: Polar Sr2TiSi2O8 glass-ceramics were prepared by recrystallizing glasses in a steep temperature gradient. The dielectric, piezoelectric and pyroelectric properties were studied as a function of temperature in the temperature range −150 to 200‡ C. The sign of the pyroelectric coefficient is positive at room temperature and is attributed to the dominance of the secondary pyroelectric effect over the primary effect. Anomalies were observed in the dielectric, pyroelectric and piezoelectric properties and a large hysteresis was observed in all these properties. Probable causes for the anomalies are discussed.
25 citations
TL;DR: In this paper, a phcnomenological theory based on the Landau-Ginsburg-Devonshirc formalism is developed to explain phase transitions in perovskite ferroelectrics with oxygen octahedron tilts.
Abstract: A phcnomenological theory, based on the Landau-Ginsburg-Devonshirc formalism is developed to explain phase transitions in perovskite ferroelectrics with oxygen octahedron tilts. In this approach, the Gibbs free energy function is expanded as a power series involving polarization and tilt angle as order parameters. After giving the general solutions, we apply the theory to the PbZr().9Ti0.1O3 system.
24 citations
TL;DR: In this paper, the pyroelectric coefficient p3 and the piezoelectric planar coupling kp and frequency constant Np in single crystal Ba2TiGe2O8 were measured and the balance evidence suggests that the transition is to a reorientable but irreversible ferroelectric phase, involving a tilt of the prototypic polar c axis.
Abstract: Measurement of the dielectric permittivity e33, the pyroelectric coefficient p3 and the piezoelectric planar coupling kp and frequency constant Np in single crystal Ba2TiGe2O8 show clear evidence of a heretofore unobserved first order phase change which occurs at - 50°C on cooling and near 0°C on heating. The balance of evidence suggests that the transition is to a reorientable but irreversible ferroelectric phase, involving a tilt of the prototypic polar c axis. The inversion of the sign of the pyroelectric effect reported earlier near 135°C is confirmed and is attributed to the changing balance between primary and secondary components in the pyroelectric coefficient.
21 citations
TL;DR: In this article, deuterium was used to grow ADTGSP and ADTGSAs and the Pyroelectric figure of merit p K and polarization P s were measured and are of the same order as those obtained on ATGSP and ATGSAs, respectively.
TL;DR: In this article, the authors extended the LGD theory for the singlecell region of the PZT solid solution system developed by Amin, et al. to include the low temperature rhombohedral phase field, which exhibits compositions having both ferroelectric polarization and tilted oxygen octahedra.
Abstract: The Landau: Ginsburg: Devonshire (LGD) theory for the singlecell region of the PZT solid solution system developed by Amin, et al.1) has been extended to include the low temperature rhombohedral phase field, which exhibits compositions having both ferroelectric polarization and tilted oxygen octahedra. An additional term has been added to the elastic Gibbs free energy to account for this tilting. The coefficients of the energy function were determined from a combination of phase boundary requirements and experimental data. The spontaneous polarization and tilt angle were calculated as a function of composition and temperature.
Abstract: The lead zirconate-titanate solid solution exhibits ferroelectric phase transitions involving tilts in its oxygen octahedral chains. A theory based on the Landau-Ginsburg-Devonshire formalism has been developed and numerical calculations have been made for the Pb Zr0.9 Ti0.1 O3 system. This approach involves expansion of the Gibbs free energy as a power series with polarization and tilt angle as order parameters. The results support the view that transitions are of first order in this system.
TL;DR: In this article, the long-range coupling may be weakened by local composition fluctuations and thus near Tc strong local fluctuations could develop in Ps, thermal strain x1, and x3, dielectric constant, K3 and optical birefringence are used to confirm that the polarization P32 is not zero for a range of temperature above c. c.
Abstract: For the materials with diffuse phase transitions it is suspected that the long-range coupling may be weakened by local composition fluctuations and thus near Tc strong local fluctuations could develop in Ps. In the case of Sr0.61Ba0.39Nb2O6 (SEN) measurements of the electric polarization. Ps, thermal strain x1, and x3, dielectric constant, K3 and optical birefringence are used to confirm that the polarization P32 is not zero for a range of temperature above c The values of P32 deduced from xi vs T and birefringence vs T, the two independent methods are in good agreement indicating substantial polarization fluctuations which decay slowly above the mean Curie temperature. c.
TL;DR: In this paper, a glass-bonded crystalline boracite composites are prepared for large area device applications. But their performance was not as good as that of TGS single crystal (1×10-5 C/m2K) at room temperature.
Abstract: Polymer and glass bonded crystalline boracite composites are prepared for large area device applications. The glass bonded composites show large pyroelectric figure of merit at room temperature and at 65°C the value becomes larger than that of TGS single crystal (1×10-5 C/m2K) measured at room temperature. Larger area boracite composites can be prepared. Such composites are easier to pole, give quite reproducible results and give higher pyroelectric figure of merit (p/K values) than the earlier reported values on Fe-I boracite single crystals.
Patent•
13 Dec 1985TL;DR: A piezoelectric ceramic polymer composite of 0-3 connectivity was proposed in this paper, where the filler was a solid solution of PbTiO3-BiFeO3.
Abstract: A piezoelectric ceramic-polymer composite of 0-3 connectivity comprises as the piezoelectric filler a solid solution of PbTiO3-BiFeO3 wherein the solid solution contains 50-80% weight of BiFeO3.
TL;DR: In this article, the low temperature dielectric properties of a particular SrTiO3-containing glass-ceramic have been investigated, and it was shown that dispersive dielectrics exhibited a dispersive constant peak over the temperature range of 85 to 100 K and relaxation type loss peaks at temperatures near 50 and 100 K.
Abstract: The low temperature dielectric properties of a particular SrTiO3-containing glass-ceramic have been investigated. This glass-ceramic exhibited a dispersive dielectric constant peak over the temperature range of 85 to 100 K and relaxation type loss peaks at temperatures near 50 and 100 K. Arrhenius plots of dielectric loss data gave activation energies of 0.054 and 0.17 eV for the lower (50 K) and higher (100 K) temperature loss mechanisms. The higher temperature loss mechanism was further analyzed by the Cole-Cole method, and a relaxation strength (Ks-K∞) of 41 was calculated. The dielectric constant peak was related to the higher temperature loss mechanism, and it was proposed that ferroic phenomena were responsible.