Muneyasu Suzuki

Bi3-xMxTiTaO9 (M = La or Nd) Ceramics with High Mechanical Quality Factor Qm

The piezoelectric, ferroelectric and dielectric properties of Nd-modified Bi3TiTaO9 (Bi3-xNdxTiTaO9, BNTT-x) (0 ≤x ≤0.75) and La-modified Bi3TiTaO9 (Bi3-xLaxTiTaO9, BLTT-x) (0 ≤x ≤1.00) ceramics were investigated and compared. The specimens were fabricated by a conventional ceramic fabrication technique. BNTT-0.50 and BLTT-0.25 ceramics showed the highest coercive field, Ec, of approximately 150 kV/cm in the BNTT and BLTT systems, respectively. Furthermore, BNTT-0.50 and BLTT-0.25 ceramics also showed the highest mechanical quality factor, Qm, of approximately 11000 in the BNTT and BLTT systems at the (33)-mode, respectively. On the basis of result of this study, it was found that both BNTT-0.50 and BLTT-0.25 are high-Qm material.

High-Performance Bi0.5Na0.5TiO3 Single Crystals Grown by High-Oxygen-Pressure Flux Method

High-PO2 (oxygen pressure) crystal growth is developed for Bi0.5Na0.5TiO3 single crystals based on defect chemistry at high temperatures. Thermogravimetric analysis shows that the vacancy formations of Bi and O at high temperatures are controlled by the surface reaction (oxygen desorption), which is suppressed at a higher PO2 . Bi0.5Na0.5TiO3 crystals grown at a PO2 of 1 MPa exhibit a saturated remanent polarization of 44 µC/cm2 along [110]cubic, suggesting a spontaneous polarization of 54 µC/cm2 along [111]cubic (polar direction) of rhombohedral Bi0.5Na0.5TiO3. High-PO2 heat treatments are proposed to be effective for fabricating high-quality and high-performance ferroelectric/piezoelectric devices using Bi-based ferroelectric oxides.

Thickness dependence of dielectric properties in bismuth layer-structured dielectrics

c-axis-oriented epitaxial SrBi4Ti4O15 and CaBi4Ti4O15 films having natural superlattice structure were grown on (001)cSrRuO3‖(001)SrTiO3 substrates by metal organic chemical vapor deposition. SrBi4Ti4O15 films suffer no degradation with a dielectric constant of 200 down to a film thickness of 15nm, which corresponds to four unit cells. Temperature coefficients of capacitance were low enough despite their high dielectric constant. They exhibited stable capacitance and superior insulating properties against applied electric field, irrespective of film thickness. These results open the door to designable size-effect-free materials with high dielectric constant having bias- and temperature-independent characteristics together with superior electrical insulation for high-density capacitor applications.

Polarization and Piezoelectric Properties of High Performance Bismuth Sodium Titanate Single Crystals Grown by High-Oxygen-Pressure Flux Method

(Bi0.5Na0.5)TiO3 (BNT) single crystals were grown by flux method at a high oxygen pressure (PO2 ) of 1 MPa, and their polarization and piezoelectric properties were investigated. BNT single crystals exhibited a saturated polarization hysteresis with remanent polarizations (Pr) of 31 µC/cm2 along [100]c, 44 µC/cm2 along [110]c and 54 µC/cm2 along [111]c. These results show that spontaneous polarization of BNT is approximately 55 µC/cm2 or larger. Strain measurements of rhombohedral BNT crystals suggest that the polarization reversal along [111]c is achieved by non-180° Ps rotation whereas that along [100]c is accomplished by 180° Ps switching.

MOCVD Growth of Bi1.5Zn1.0Nb1.5O7 (BZN) Epitaxial Thin Films and Their Electrical Properties

Bi1.5Zn1.0Nb1.5O7 (BZN) epitaxial thin films were prepared on (111)Pt∥(001)Al2O3 substrates at 500°C by metal organic chemical vapor deposition (MOCVD). The electrical properties of the as-deposited films were investigated by comparing them with those of the (111)-one-axis-oriented films prepared on (111)Pt/TiO2/SiO2/(100)Si substrates for making a Pt/BZN/Pt capacitor structure. The relative dielectric constant of the epitaxial film was almost the same as that of the one-axis-oriented one, but its changes with frequency dependence and tan δ were smaller than those of the one-axis-oriented one.

Low strain sensitivity of the dielectric property of pyrochlore Bi–Zn–Nb–O films

Thermal strain sensitivity of the dielectric property was investigated for (111)-textured polycrystalline Bi-Zn-Nb-O films. Cubic pyrochlore films with similar crystallinity and the degree of the orientation were obtained on various substrates, and their 111 lattice spacing monotonously increased with the increasing thermal expansion coefficient of the substrates. The dielectric constant at 0 kV/cm and its tunability were almost independent of the residual strain, unlike highly sensitive (Ba0.5Sr0.5)TiO3 films. This strain independent characteristic of the dielectric property of pyrochlore Bi-Zn-Nb-O film is a big advantage in actual applications. 0 2008 American Institute of Physics.

Temperature Dependence of Dielectric Properties of Barium Titanate Ceramic Films Prepared by Aerosol Deposition Method

BaTiO3 (BTO) thick films were deposited by an aerosol deposition (AD) method and their physical and electrical properties were investigated. The films were deposited on Pt/Ti/Al2O3 and Pt/Ti/ZrO2 (YSZ) ceramic substrates at a thickness of approximately 2 µm. Two powders were selected for this investigation. The primary BTO powders have a perovskite structure with average particle diameters of 0.1 and 0.5 µm, respectively, and are commercially available as raw powders (BT01 and BT05). These powders were heat-treated for 1 h at 1000 °C in a furnace prior to deposition. The particle size was not changed by the heat treatment while a large aggregate with a size of 10–50 µm was observed in the heat-treated BT01 powder. As-deposition films showed a relative dielectric constant (er) of approximately 100 regardless of the powder and the substrates used. A post-deposition heat treatment at 1000 °C for 1 h was carried out for the BTO thick films. After annealing, the er was improved. The BTO thick films prepared from BT01 heat-treated powders on the Pt/Ti/YSZ ceramic substrates showed an er at room temperature of 1120 which is higher than that of 910 of the films deposited on Pt/Ti/Al2O3. The BTO films fabricated from BT05 heat-treated powders on Pt/Ti/Al2O3 ceramic substrates have an er of 650, larger than that for the films deposited on Pt/Ti/YSZ. Control of powder aggregation by heat treatment along with the use of AD as the method of film fabrication and appropriate substrate selection are demonstrated to be important parameters to obtain BTO ceramic films with a high er.

Piezoelectric Properties of Lanthanum Modified Bi3TiTaO9 Ceramics

ABSTRACT La modified Bi 3TiTaO9 ceramics (Bi 3-xLaxTITaO9, BLTT-x) were fabricated by the conventional ceramic fabrication technique. The Curie temperature, Tc, decreased with increasing amount of La ions. In term of ferroelectric properties, BLTT-0.25 had the highest coercive field (Ec = 150 kV/cm). The mechanical quality factor, Qm, of this ceramic is high at 11000. The coupling factor, k33, of BLTT-0.25 and BLTT-0.37 was 14 %.

Fabrication and Characterization of Optical Micro-Electro-Mechanical System Scanning Devices Using BaTiO3-Based Lead-Free Piezoelectric-Coated Substrate Sheet by Aerosol Deposition

We demonstrated high-speed metal-based Lamb-wave-resonance piezoelectric-drive optical micro-electric-mechanical system (MEMS) scanning devices using lead-free piezoelectric direct coated substrate sheets. The BaTiO3-based lead-free piezoelectric direct coated substrate sheet prepared by aerosol deposition achieved a piezoelectric d31 of approximately -138 pm/V. The metal-based optical scanning devices have a 1 mm circular mirror. Under the ambient air, the wide optical scanning angle of 58° and the high resonance frequency of 26.681 kHz were achieved at the applied voltage of less than 30 V.

Growth Behavior of

c-Axis-oriented ultra thin SrBi2Ta2O9 films were epitaxially grown on atomically flat (100)SrTiO3 substrates by pulse-gas-introduced metalorganic chemical vapor deposition, and their growth behavior was observed by atomic force microscopy (AFM). Growth-time-resolved AFM images clearly showed that a completely filled SrBi2Ta2O9 layer was laid under an incompletely grown half-unit-cell two-dimensional (2D)-island layer, indicating the Frank–van der Merwe (layer-by-layer) growth mode. This is the first step-by-step direct observation of layer-by-layer growth of c-axis-oriented bismuth layer-structured dielectric (BLD) films and is considered to be the origin of the thickness-independent smooth surface of c-axis-oriented BLD films.