Masatomo Yonezawa

Internal electrode piezoelectric ceramic actuator

Abstract A piezoelectric ceramic actuator element with multilayer internal electrodes has been investigated. It was fabricated by multilayer ceramic capacitor techniques. An individual internal electrode has the same area as the element cross section area. It has no piezoelectric inactive part, so that it shows original strain/field characteristics in the material. It can be driven by a relatively low votlage (< 200V) and has a semi-permanent life under successive voltage pulse application. Typical properties of the element using 0·65Pb(Mg1/3Nb2/3)O3-0·35PbTiO3 ceramics are 8·7 × 10−4 strain, over 3·5 × 107 N/m2 force, within 100 μsec response time and 70% electromechanical couplig factor driven by 1 × 106 V/m field.

Synthesis and properties of ultrafine AlN powder by rf plasma

High‐purity ultrafine AlN powder was synthesized by rf plasma through direct nitridation of Al. The specific surface area was about 30 m2 /g under typical experimental conditions. Ultrafine AlN powder showed excellent sinterability, compared with conventional AlN powders, whose particle sizes were more than 0.5 μm. The thermal conductivity for the sintered body reached 220 W/m K when sintered at 1900 °C, and 110 W/m K when sintered at 1400 °C, by using YF3 as a sintering aid.

Effect of oxygen deficiency on the crystal structure and superconducting properties of the Ba2YCu3Oy

Effect of oxygen deficiency on crystal structure and superconductivity of Ba2YCu3O7-δ was studied by annealing and quenching experiments. With increasing oxygen deficiency superconductivity was suppressed remarkably while axial ratio, a0/b0 in the orthorhombic phase approached to unity and c0 value increased. Structural transformation from orthorhombic to tetragonal lattice took place in the temperature range, 950~980°C and maximum oxygen deficiency, δ=0.7 was observed for the tetragonal phase.

Determination of the Orthorhombic-Tetragonal YBa2Cu3O7-δ Phase Boundary in the δ-T Diagram

The orthorhombic-tetragonal YBa2Cu3O7-δ phase boundary in the δ-T diagram was determined by a detailed isobar TG measurement under the oxygen partial pressures of 1 to 0.01 atm. The phase boundary was found not to be located at δ = const., but to have a slope of dδ/dT~-4.7×10-4 K-1. The experimental results are discussed with a simple order-disorder transformation model of oxygen atoms on the Cu plane sandwiched by Ba planes.

Internal Electrode Piezoelectric Ceramic Actuator

An internal electrode multilayer piezoelectric ceramic actuator element has been investigated. An individual internal electrode has the same area as the element cross section area. It has no piezoelectric inactive part, so that it shows strain/field characteristics similar to plain piezoelectric ceramics. It can be driven by a relatively low voltage (200 V) and has a semipermanent life under a successive voltage pulse application. Typical properties of the element using 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 ceramics are 8.7×10-4 strain, over 3.5×107 N/m2 stress and within 100 µsec response time driven by 1×106 V/m field.

New Low-Firing materials for multilayer capacitors

Abstract The Pb(Ni1/3,Nb2/3)O3-Pb(Mgl/2Wl/2,)O3-PbTiO3 ternary system was studied for use as a multilayer capacitor material. Compositions with a high dielectric constant (e > 10000) and high specific resistivity can be fired at temperatures below 1050° C in this system. Chip capacitors made of one of these materials, with 85%Ag-15%Pd inner electrodes, are fired at 960°C and show good electrical properties and reliability.

Properties of carbon films by dc plasma deposition

Perfectly smooth transparent carbon films deposit onto room‐temperature silicon wafers in a dc plasma of methane (CH4) and hydrogen (H2). Transmission electron microscope analysis reveals that the films consist primarily of amorphous carbon (a‐C). The nearest neighbor C–C bond length of a‐C formed at low discharge current densities or low working pressures approaches that of diamond. Electrical resistivity, calculated using V‐I curves for the Al‐C‐Si structure, is more than 1013 Ω cm. A face‐centered‐cubic phase with a lattice constant of 4.96 A and diamond, both of which form at relatively high pressures, consist of crystallites having a diameter of about 100 A.

The Orthorhombic-Tetragonal Phase Transformation and Oxygen Deficiency in LnBa2Cu3O7-δ

The orthorhombic-tetragonal phase transformation in LnBa2Cu3O7-δ (Ln=Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) was studied using careful isobar TG measurements under an oxygen partial pressure of 1 atm. As the atomic number within the lanthanide series increases, the transformation temperature tends to increase as well. This tendency is strongly related to the spacing of the nearest-neighbor oxygen atoms and is successfully interpreted in terms of the repulsion energy between them on the basis of a simple order-disorder transformation model proposed in our previous paper.

Properties of the Large-Capacitance Multilayer Ceramic Capacitor

Electrical properties of the large-capacitance multilayer ceramic capacitor made of the ceramics of Pb(Fe2/3W1/3)O3–Pb(Fe1/2Nb1/2)O3 system were studied. The ceramics are sintered at 900°C in air, and therefore, it is possible to use Ag–Pd alloy as the internal electrode. The size of the capacitor with capacitance of 400 µF is fairly small. Dissipation factor is extremely small (0.6%) under the D.C. voltage bias in wide frequency range. Insulation resistance is more than 6000 M Ω µF. Impedance at high frequency band is small compared with those of other electrolytic capacitors with the same capacitance. Electrical properties are hardly changed in lifetime test.

Research and development of relaxor ferroelectric ceramics at NEC

The authors describe the development of many systems containing relaxor ferroelectrics studied for multilayer ceramic capacitors at NEC Corporation since 1975. These ceramics were composed of complex perovskite compound containing lead ion and were categorized into three types. The complex perovskite systems containing Pb ions and W ions were suitable for a low firing temperature and showed a high dielectric constant with a smaller grain size than a BaTiO/sub 3/ system. Multilayer capacitors with large capacitance have been manufactured from these systems. Pyrochlore compound was effective for suppression of grain growth and resulted in bend strength increases, The use of alkoxide powder was very promising. The multilayer ceramic capacitors made from this powder showed a very high capacitance per volume.<<ETX>>