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Yoshihiro Ishibashi,Makoto Iwata 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9
The morphtropic phase boundary existing in a perovskite-type solid solution like Pb(Zr,Ti)O3 (PZT) is reconsidered in relation to the order of the ferroelectric phase transition. For the secondorder transition from the paraelectric cubic phase, at the triple point S where the cubic, tetragonal and rhombohedral phases meet, the free energy is isotropic in the order parameter space, and a vertical boundary guarantees dielectrically excellent properties, while for the first-order transition, at the triple point F, the free energy is usually anisotropic, and even a vertical boundary does not necessarily guarantee the best properties.
Phase Diagram in Pb(Zn_(1/3)Nb_(2/3))O_3-8%PbTiO_3 under an Electric Field
Makoto Iwata,Sadaharu Kato,Yoshihiro Ishibashi 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.31
The phase diagram near the critical endpoint (CEP) in Pb(Zn_(1/3)Nb_(2/3))O_3-8%PbTiO_3 under anelectric field was investigated by measuring the DC field dependence of the dielectric constant along the [001] direction. The CEP under an electric field along the [001] direction was determined to be 170 ± 2 ℃ and 1.5 ± 0.2 kV/cm.
Makoto Iwata,Ryo Nagahashi,Masaki Maeda,Yoshihiro Ishibashi 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.9
The temperature and the DC biasing-field dependences of the dielectric permittivities along the [001]c, [011]c, and [111]c directions of the pseudocubic coordinates have been investigated in Pb(Zn1/3Nb2/3)O3-xPbTiO3 (x = 6%). The temperature-electric-field phase diagrams have been clarified in the field range below 8 kV/cm. The critical endpoint has been found at 1.3 kV/cm and 164 ◦ C for an electric field applied along the [001]c direction. The concentration dependences of the critical temperature and the transition temperature are discussed. The expected transition temperature T0(x) at which the second-order phase transition would occur is shown to be determined by the transition temperature TCT (x) and the critical temperature TCEP (x).
Makoto Iwata,Sadaharu Kato,Kazuki Tanaka,Masaki Maeda,Yoshihiro Ishibashi 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.7
Dielectric constants as functions of the temperature and the DC biasing fields along the [011] and the [111] directions in cubic coordinates in 92%Pb(Zn<SUB>1/3</SUB>Nb<SUB>2/3</SUB>)O<SUB>3</SUB>-8%PbTiO<SUB>3</SUB> (PZN-8%PT) have been investigated. The temperature-field phase diagrams have been made in the field range below 15 kV/cm. We have found that the orthorhombic phase exists below the tetragonal phase as a ground state. The tetragonal phase disappears for external fields above about 10 kV/cm along the [011] and the [111] directions.
Makoto Iwata,Hidehiro Ohwa,Ikuo Suzuki,Maeda Masaki,Naohiko Yasuda,Yoshihiro Ishibashi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Domain-wall structures on an etched surface of the PZN-20 %PT crystal were investigated by the scanning probe microscopy (SPM). It was shown that 90 and 180 domain-wall structures can be observed. The surface charge due to the spontaneous polarization was detected by the electrostatic force microscopy (EFM). It was found that there exist complex 180 domain-wall structures with typical size of 1 m order on the (001)-crystal surface of the PZN-20 %PT.
Ferroelectric Domain Wall Structure in Pb(Zn1/3Nb2/3)O3-PbTiO3 Mixed Crystals by AFM
Makoto Iwata,Ikuo Suzuki,Kohei Katsuraya,Maeda Masaki,Naohiko Yasuda,Yoshihiro Ishibashi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Domain-wall structures in Pb(Zn1=3Nb2=3)O3-xPbTiO3 (PZN-xPT; x = 0 %, 8 %, 20 %) crystals were investigated by using atomic force microscopy (AFM). Ferroelectric and ferroelastic domainwallstructures were observed on the etched surface. In the rhombohedral phase, a zigzag domainwall structure was newly found. We showed that all of the ferroelastic domain-wall structures observed in the tetragonal and rhombohedral phases can be explained by the Sapriel theory, and concluded that no ferroelectric charged domain-wall exists in the PZN-xPT (x = 8 %, 20 %) crystal without an external eld. The symmetry of the crystal phase in PZN-8 %PT at room temperature is discussed. It was also found that the ngerprint pattern in PZN disappears after the poling process, even in a weak eld of about 50 V/cm, which is about 1/20 of the coercive field.
Polarization Reversals with 90o Domain Walls in Bi4Ti3O12
Makoto Iwata,Ikuo Suzuki,Maeda Masaki,Nohiko Yasuda,Rintaro Aoyagi,Yoshihiro Ishibashi 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Polarization reversal processes with 90 domain walls under a low-frequency field of 25 mHz were investigated on the ab-plane in the ferroelectric Bi4Ti3O12 crystal by using a polarizing microscope. We found that there are three kinds of modes in the polarization reversal of the a-domain, that is, changes of the width in a-domains, annihilations of needle-like a-domains, and polarization reversals within the a-domain. We point out that the a-domain in the 90 domain wall structure plays an important role in the polarization reversal process under a field along the b direction.X%1
Pressure Eect of Dielectric Property in Solid Solutions (1-x)Pb(Mg1=3Nb2=3)O3 - xPbZrO3
Hidehiro Ohwa,Naohiko Yasuda,Makoto Iwata,Hiroshi Orihara,Yoshihiro Ishibashi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Dielectric properties of the solid solution system (1-x)Pb(Mg1=3Nb2=3)O3-xPbZrO3 have been studied under hydrostatic pressures up to 0.6 GPa. For the concentration of x 0:8, the values of the dielectric maximum and the temperature of the dielectric maximum decrease at the rate of about
Naohiko Yasuda,Hidehiro Ohwa,Makoto Iwata,Mituyoshi Matushita,Yohachi Yamashita,Yoshihiro Ishibashi,Yuuki Itoh 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
The piezoelectric properties of a Pb[(Zn1=3Nb2=3)0:91]Ti0:09O3 single crystal along the [001] direction in the rhombohedral phase were investigated under pressures of up to 500 MPa. The pressure dependence of electromechanical coupling factors in the k31 and k33 mode, k31 and k33, the resonance frequency fr and the antiresonance frequency fa, elastic compliances s11 E and s33 E, and the mechanical quality factor Qm are presented. The k31 decreases greatly with pressure, while the k33 decreases slightly.