Senji Shimanuki

An Improved Phased Array Ultrasonic Probe Using 0.91Pb(Zn1/3Nb2/3)O3?0.09PbTiO3 Single Crystal

A 96-channel phased array probe for echocardiography using a single-plate, 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 (PZNT 91/9) single-crystal transducer with dimensions of 14×20 mm has been fabricated to realize greater sensitivity and broader bandwidth properties. The center frequency of the probe, 3.5 MHz, was selected to cover the bandwidths of two conventional lead zirconate titanate (PZT) ceramic probes with center frequencies of 2.5 and 3.75 MHz. A solder paste was used to connect a flexible printed circuit to the PZNT 91/9 transducer. The echo amplitude of the PZNT 91/9 probe is about 6 dB higher than that of the two PZT probes, and the fractional bandwidths are 30 and 25 percentage points wider, respectively. The B-mode image quality of the PZNT 91/9 probe is comparable to that of the two PZT probes, and the Doppler sensitivity of the PZNT 91/9 probe is almost equal to that of the 2.5 MHz PZT probe, which means that the PZNT 91/9 probe matches both the penetration of the 2.5 MHz PZT probe and the resolution of 3.75 MHz PZT probe.

A 3.7 MHz phased array probe using 0.91Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.09PbTiO/sub 3/

A novel 128-channel phased array probe for echocardiography with a center frequency of 3.7 MHz using 0.91Pb(Zn(1/3)Nb(2/3))O(3)-0.09PbTiO(3 ) (PZN-9%PT) single crystal has been fabricated to realize greater sensitivity and broader bandwidth properties. The echo amplitude of the PZN-9%PT single-crystal probe is about 5 dB higher than that of the conventional lead airconate titanate (PZT) ceramic probe, and the fractional bandwidth is about 25 percentage points broader. The quality of B mode images obtained by the PZN-9%PT probe satisfies the performance of the two types of conventional PZT ceramic probes that have center frequencies of 2.5 and 3.75 MHz. At the reference frequency of 3 MHz, the Doppler sensitivity of the PZN-9%PT probe is about 5 dB higher than that of the 3.75 MHz PZT probe; the blood flow of a pulmonary vein in a hard-to-image patient is much more clearly imaged than in the case of using the PZT probe. These superior images are attributable to the use of sufficiently large PZN-9%PT single crystals obtained by the self-flux method.

Synthesis of lead scandium niobate-lead titanate pseudo binary system single crystals

Single crystals of the Pb[(Sc{sub 1/2}Nb{sub 1/2}){sub 1{minus}x}Ti{sub x}]O{sub 3} (PSNT) pseudo binary system have been successfully obtained by a flux method using PbO-B{sub 2}OI{sub 3} flux. The crystals were grown in a platinum crucible by mass crystallization, achieved by slow cooling the solution at 3C/h from 1,200 to 800 C. The resulting crystals are 2 to 7 mm in length. Chemical analysis and X-ray studies revealed that the crystals are of the Perovskite structure with x = 0.33 to 0.37, making them slightly different from the charged polycrystalline composition of a morphotropic phase boundary, where x = 0.42.

A 20 MHz single-element ultrasonic probe using 0.91Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.09PbTiO/sub 3/ single crystal

A 20 MHz single-element ultrasonic probe using 0.91Pb(Zn(1/3 )Nb(2/3))O(3)-0.09PbTiO(3) (PZN-PT 91/9) single crystal has been fabricated. The single crystal of PZN-PT 91/9 orientated to the (001) plane has longitudinal coupling factor of k(33)>90%, which is much larger than the k(33)=70 to 80% of conventional Pb(Zr(1-x),Ti(x))O(3) (PZT) based ceramics. A single crystal of PZN-PT 91/9 without inclusion or crack has been grown with dimensions of about 25x15x5 mm by the self-flux method. Because mechanical strength in the fabrication of disk transducers orientated to the (001) plane was sufficiently strong, under the same conditions as are applied to conventional PZT ceramics, a piston single-element probe with a diameter of 2.0 mm and a frequency of 20 MHz was successfully fabricated. The bandwidth of the PZN-PT 91/9 probe was 13-26 MHz, which was 4 MHz broader than that of the conventional PZT probe.

Forty-channel phased array ultrasonic probe using 0.91Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.09PbTiO/sub 3/ single crystal

A 0.91Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.09PbTiO/sub 3/ (PZN-PT) single crystal with high electromechanical coupling factor (k/sub 33/)>90% has been used to fabricate a 40-channel phased array ultrasonic probe with greater sensitivity and broader bandwidth than conventional probes. This probe has a center frequency of 3.5 MHz and an aperture of about 6.0/spl times/7.5 mm. The standard probe fabrication process was modified for PZN-PT. The dispersion of echo signals was within /spl plusmn/20% of the mean value. After recovery poling, the echo amplitude of the PZN-PT single-crystal probe is 8 and 5 dB higher than that of one- and two-matching-layer PZT probes, respectively. Moreover, the fractional bandwidth of the single-matching-layer PZN-PT probe is broader than that of the two-matching-layer PZT probes. The PZN-PT single crystals provide great improvements in the sensitivity and bandwidth of phased array probes.

Simulation and Fabrication Process for a Medical Phased Array Ultrasonic Probe using a 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 Single Crystal

Medical array ultrasonic probes using a 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 (PZN-PT) single crystal exhibiting a high electromechanical coupling factor (k33) >90% have been studied in order to realize both a higher sensitivity and broader bandwidth properties. Pulse echo characteristics of the array probes, each transducer of which has dimensions of 6.0 mm×0.14 mm with a center frequency of 3.5 MHz, are simulated using the dielectric and the piezoelectric constants of the grown PZN-PT single crystals. Simulated echo amplitudes of the PZN-PT probes have been improved by as much as 7 dB compared with those of the conventional Pb(Zr1-x,Tix)O3 (PZT) ceramic ones. Moreover, the bandwidth of the PZN-PT probe is expected to be about 25% broader than those of the conventional PZT probes. It has been shown by simulation that the low acoustic impedance as well as the high coupling factor of the PZN-PT crystal contribute in broadening the bandwidth of the probe. The fabrication process of the array probe was investigated. A conventional method in which the dicing conditions are optimized and a novel dicing process are proposed.

Crystal Growth and Mechanical Properties of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 Single Crystal Produced by Solution Bridgman Method

High-quality, 40-mm-diameter piezoelectric Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystals (PZNT91/9) were successfully grown by the solution Bridgman method. Vickers hardness and fracture toughness of a PZNT91/9 wafer cut from a crystal were investigated by a microindentation technique. The Vickers hardness of PZNT91/9 was 2.6 GPa (transparent area) and 2.2 GPa (opaque area). The Vickers hardness of the transparent area in PZNT91/9 was equivalent to that of PZT ceramic. The fracture toughness of the transparent area of PZNT91/9 was markedly different depending on the domain direction: KIC=0.80 MPam1/2 (vertical to the domain wall); and KIC=0.38 MPam1/2 (parallel to the domain wall). Although the fracture toughness of PZNT91/9 is smaller than that of PZT ceramic, it is possible to cut the crystals for fine-pitch dicing, as required to produce array-type medical transducers, without serious problems.

Oriented grain growth from lead germanate glasses

Oriented pyroelectric glass-ceramics were prepared by crystallizing the glass in the PbO-GeO2 system. The high degree of c-plane orientation of Pb5Ge3O11 crystallites was obtained in the thin sample when crystallized near the eutectic temperature. The degree of orientation depended on composition, annealing temperature and time.

Substituted Amorphous Co–Fe–Si–B Alloys

The substitution effects of Cr, Nb and a commercial 42 at.% Nb–Ni on the magnetic properties of amorphous (Co–Fe)75Si10B15 alloys are studied. It is shown that substitutions of these metals increase the crystallization temperature. hardness and electrical resistivity, and improve soft magnetic properties. It is also shown that the appropriate Fe and 42 at.% Nb–Ni contents are beneficial for the improvement of the thermal stability of coercive force and of effective permeability.

Single-element ultrasonic probe using PZN-PT single crystal

In order to improve the sensitivity and the bandwidth of an ultrasonic probe, the single-element probe using single crystals of the solid solution Pb(Zn1/3Nb2/3)O3- PbTiO3 (PZN-PT) has been investigated. Single crystals of PZN-PT with 9 mol% PbTiO3 (PZN-PT 91/9) single crystals were grown by the self flux method using PbO-based flux. It was confirmed that the single crystal of good quality with the dimensions of about 25 multiplied by 15 multiplied by 5 mm which is capable of fabricating a phased array probe for echocardiography has been grown. As a first step, a plane single-element probe of 2.0 mm in diameter and 20 MHz was fabricated for gastrointestinal lesions. Mechanical strength of the new crystal material in the fabricating process was strong enough since no damage such as cracking occurred. The sensitivity of the PZN-PT probe has been improved compared with that of the conventional PZT one. Also,the bandwidth has been noticeably broadened.