Tsutomu Ochiai

Electromechanical Properties of Poly-L-Lactic Acid

The electromechanical coupling coefficient, the piezoelectric constant, the elastic compliance constant and the mechanical quality factor for a poly-L-lactic acid (PLLA) plate elongated to 4 times the original length were determined by a self-resonant method. k14=0.064, d14=9.82×10-12 C/N, s44E=9.28×10-10 m2/N and Qm=30.3 were obtained at room temperature for a 0° X-cut square plate. It is noted that elongated PLLA films have no spontaneous polarization, unlike poled polymers such as poly(vinylidene fluoride) (PVDF), but still have a large shear piezoelectric constant.

Acoustic and Ferro- and Antiferroelectric Properties near Phase Transition Temperatures of Modified PbZrxTi1-xO3-based Ceramics

Acoustic and ferroelectric properties were obtained using an ultrasonic pulse-echo-overlap method, a self-resonator method and a composite-bar resonator method for ferroelectric ceramics 0.08(SrLa0.5Nb0.5O3)–0.92(PbZr0.53Ti0.47O3), Pb0.902La0.098–(Zr0.55Ti0.45)0.976O3, Pb1-xLax(ZryTi1-y)1-x/4O3 and x(BaCa1/3Nb2/3O3)–(1-x)(PbZr0.975Ti0.025O3). Ferro- and antiferroelectric properties were also obtained for the last one. Ultrasonic attenuations in some of these ceramics are discussed, related to grain and domain symmetries observed through a transparent electron microscope.

DEVELOPMENT OF PIEZOELECTRIC ACCELEROMETER OF CHARGE-SHEAR TYPE HAVING TEMPERATURE-INDEPENDENT SENSITIVITY

A piezoelectric accelerometer based on detecting piezoelectric charge Q1 caused by shear strain S5 has been developed, which consists of two piezoelectric elements made from a ferroelectric ceramic and one condenser element also made from a ferroelectric ceramic. Positive temperature dependence of dielectric constant of the former piezoelectric element (PbZr0.51Ti0.49O3 modified with 0.7 mol% Nb2O5) is compensated by negative dependence of the latter condenser element [Pb0.8La0.2(Zr0.4Ti0.6)0.95O3 or Pb0.7Sr0.2La0.1(Zr0.5Ti0.5)0.975O3] over a range of -50 to 300°C, with the result that sensitivity and its deviation are obtained to be 42×10-12 C/G and within 5%, respectively.

Determination of Elastic Stiffness and Piezoelectric e- and d-Constants of Piezoelectric Ceramic from Ultrasonic Velocity and Dielectric Constant

Ultrasonic velocities and dielectric constants were measured along different directions on the X-Z plane of a Pb(Zr0.52Ti0.48)O3 ceramic (poling direction is along the Z-axis). A complete set of values of elastic stiffness constants and piezoelectric e- and d-constants have been obtained by the least squares method from the velocities and dielectric constants.

Electrical and Optical Properties of Hot-Pressed Ba(La1/2Nb1/2)O3–PbZrO3–PbTiO3 Ceramics

Hot-pressed ceramics of the solid solution in the ternary systems xBa(La1/2Nb1/2)O3–(1-x)[Pb(ZryTi1-y)O3] show excellent optical and electrooptical characteristics, comparable to PLZT. Linear and quadratic electrooptical coefficients, rc and R, are determined for more than ten specimens of various compositions near the morphotropic phase boundary between the tetragonal and the rhombohedral phases and maximum values of rc=10.73×10-10m/V and R=12.0×10-16 m2/V2 are observed. Dielectric and electromechanical measurements along with X-ray analysis are also carried out to determine the phase diagram.

Elastic Properties of Rhombohedral PLZT Ceramics

Elastic compliance constants, elastic stiffness constants, electro-mechanical coupling coefficients, mechanical losses and thermal expansion coefficients have been obtained for lanthanum doped lead zirconate-titanate ceramics having composition of (X/65/35) with X=1 to 7.5 (abbreviated to rhombohedral PLZT) over a temperature range including the Curie point and ferroelectric-ferroelectric phase transition point (so-called FE1FE2 point) existing in the rhombohedral ferroelectric phase. All measured constants have definite anomalies at the Curie point but only elastic constants s33 and c33 have anomalies at the FE1-FE2 point. Phenomena observed for the rhombohedral PLZT were found much different from those for the tetragonal PLZT and other systems.

Electrical and Optical Properties of Hot-Pressed AαNb2(3-α)/5O3-PbZrO3-PbTiO3 (A= Ba, Sr) Ceramics

A new electrooptic ceramic (Pb1-xAαx) {Nb2(3-α)x/5(ZryTi1-y)1-x}O3 is proposed, where A=Ba or Sr. These ceramics sintered by the conventional hot-pressing method exhibit excellent optical chracteristics; namely their transmittances and transverse linear electrooptic coefficients being comparable to those of PLZT. Compositional and/or temperature dependences of dielectric constants, electromechanical coupling factors and lattice parameters have been measureed to elucidate the phase bondaries of these systems. It is also shown that lattice bacancies in the Pb sites deteriorate optical transparency considerably.

Electrical and Optical Properties of Hot-Pressed A(Zn1/3Nb2/3)O3–PbTiO3–PbZrO3 (A= Ba, Sr, Ca) Ceramics

Electrical and optical properties of hot-pressed ceramics in ternary systems A(Zn1/3Nb2/3)O3–PbTiO3–PbZrO3, where A=Ba, Sr or Ca, have been studied and it has been found that optical transmittances of these ceramics (0.24 mm thick) are more than 60% at 600 nm, and that electromechanical coupling coefficients k31 are as high as 42% with mechanical quality factors QM as low as 27, near the morphotropic boundary between the tetragonal and the rhombohedral phases. The phase diagram of the ternary system Sr(Zn1/3Nb2/3)O3–Pb(Ti–Zr)O3 has been determined from X-ray analysis combined with dielectric measurements.