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The lattice dynamics of solid 4He has been explored using pulsed NMR methods to study the motion of 3He impurities in the temperature range (0.05-0.20 K) where experiments have revealed anomalies attributed to superflow or unexpected viscoelastic properties of the solid 4He lattice. We report the results of measurements of the nuclear spin-lattice and spin-spin relaxation times that measure the fluctuation spectrum at high and low frequencies, respectively, of the 3He motion that results from quantum tunneling in the 4He matrix. The measurements were made for 3He concentrations 16 < x3 < 2000 ppm. For 3He concentrations X3 = 16 and 24 ppm, large changes are observed for both the spin-lattice relaxation time T1 and the spin-spin relaxation time T2 at temperatures close to those for which the anomalies are observed in measurements of torsional oscillator responses and the shear modulus. These changes in the NMR relaxation rates were not observed for higher 3He concentrations. [ABSTRACT FROM AUTHOR]

(Na0.53+x K0.47)(Nb0.55Ta0.45)O3 (NKNT) ceramics prepared by a solid state process were investigated at 0 ≤ x ≤ 0.02 to determine the effects of Na content in NKNT ceramics. With Na nonstoichiometry, piezoelectric properties were varied but grains were all cube-like perovskites with no impurity phases. Piezoelectric coefficient (d 33) was sensitive to Na content while polymorphic phase transition (PPT) temperature was not. PPT temperature between orthorhombic and tetragonal phases (T O-T) was around room temperature within the compositional range tested. The highest d 33 obtained was 330 pC/N at Na0.545 (x = 0.015) increased from 310 pC/N at Na0.53 (x = 0), which was due to the morphotropic phase boundary (MPB) effect around (Na0.53K0.47) of NKNT ceramics. [ABSTRACT FROM AUTHOR]

The effects of Li substitution on K in (Na0.53K0.47-x Li x )NbO3 (NKLN) ceramics prepared by a solid state process were studied at 0 ≤ x ≤ 0.09. Phase purity was maintained up to x = 0.04, then a secondary phase started emerging. With increasing Li substitution, partial melting appeared to occur and grain size increased. Polymorphic phase transition (PPT) temperatures, T O-T between orthorhombic and tetragonal phases and T C between tetragonal and cubic phases, were significantly affected by Li substitution. With increasing x, T O-T decreased while T C increased extending the tetragonal phase region. The highest d 33 of 220 pC/N was obtained at x = 0.07 mol at which high apparent density of the sintered pellets was obtained despite the formation of an impurity phase. [ABSTRACT FROM AUTHOR]

Ferroelectric K0.5Bi4.5Ti4O15 (KBTi) and Cr-doped K0.5Bi4.5Ti4O15 ((K0.5Bi4.5Ti3.97 Cr0.03O15-δ), (KBTC)) thin films were prepared on Pt(111)/Ti/SiO2/Si substrates by using a chemical solution deposition method. The thin films were annealed at 750°C for 3 min by a rapid thermal annealing process under oxygen atmosphere. Compared to pure KBTi thin film, there was no structural change while improved ferroelectric and leakage current properties were observed. The values of remnant polarization (2Pr ) and coercive field (2Ec ) were 50.9 μC/cm2 and 244 kV/cm at an applied electric field of 300 kV/cm, respectively. The 2Pr we observed is compatible with that of doped bismuth layer-structured ferroelectric thin films. Leakage current density was 6.00 × 10−7 A/cm2 at 200 kV/cm. The enhanced properties of KBTC could be explained by a defect dipole (Cr′Ti-V) and increased average grain size. [ABSTRACT FROM AUTHOR]

Ferroelectric Na0.5Bi4.5Ti4O15 (NaBTi) thin films, selectively controlled in c-axis and random orientation, were fabricated on a Pt(111)/Ti/SiO2/Si(100) substrate by using a chemical solution deposition method. The preferred orientation of the thin films annealed at 750°C under oxygen atmosphere was confirmed by X-ray diffraction and scanning electron microscope studies. We found that ferroelectric, dielectric, and leakage current properties were strongly related to the crystallographic orientation of NaBTi thin films; the randomly oriented NaBTi thin film exhibited better properties than the c-axis oriented thin film. The values of remnant polarization (2Pr), dielectric constant, and leakage current density were 21 μC/cm2 at 300 kV/cm, 630 at 100 kHz, and 7.4 × 10-6 A/cm2 at 100 kV/cm for the randomly oriented thin film, respectively, and 6 μC/cm2, 420, and 1.1 × 10-1 A/cm2 for the c-axis oriented thin film, respectively. Also, no polarization fatigue was observed in both NaBTi thin films up to 107 switching cycles. [ABSTRACT FROM AUTHOR]

Ferroelectric CaBi4Ti4O15 (CBTi) thin films with random orientation and high c-axis orientation were prepared on a Pt(111)/Ti/SiO2/Si(100) substrate by a chemical solution deposition method. We observed a strong dependence of ferroelectric and dielectric properties on the film orientation. The CBTi thin film with random orientation exhibited remnant polarization (2Pr) of 54 μ C/cm2 at an applied electric field of 250 kV/cm and dielectric constant (ε) of 412 at a frequency of 1 kHz. The values of 2Pr and ε were larger than those observed in the CBTi thin film with high c-axis orientation. In addition, the randomly oriented thin film showed lower leakage current density than the highly c-axis-oriented thin film. [ABSTRACT FROM AUTHOR]

SrBi5FeTi4O18 (SBFT) thin films were prepared on a Pt(111)/Ti/SiO2/Si(100) substrate using a chemical solution deposition method and annealed at 650°C under oxygen atmosphere. It was found that the polycrystalline SBFT thin film exhibits good ferroelectric properties. The values of remnant polarization (2Pr) and coercive electric field (2Ec) were 33 μ C/cm2 and 150 kV/cm at an applied electric field of 250 kV/cm, respectively. Leakage current density of the thin film was 106 A/cm2 at 100 kV/cm. The values of dielectric constant and dielectric loss were 470 and 0.05 at 1 kHz, respectively. No significant polarization fatigue was observed up to 1.44 × 1010 switching cycles. Also weak ferromagnetic properties were observed. [ABSTRACT FROM AUTHOR]

Nd-substituted bismuth titanate Bi3.54Nd0.46Ti3O12 (BNT) thin films were prepared on (111)Pt/Ti/SiO2/Si substrates by a sol–gel method. The BNT thin films processed at a low annealing temperature of ∼600 °C showed good ferroelectric properties. The randomly oriented BNT single phases and the improved ferroelectric properties were confirmed by X-ray diffraction and polarization–electric field hysteresis loops, respectively. The remanent polarization of the BNT thin films is 64 μC/cm2, which is larger than that of Bi3.25La0.75Ti3O12 (BLT) thin films. After 1010 read/write switching cycles, the effective non-volatile charges showed no polarization fatigue. Regardless of the low annealing temperature of 600 °C, the BNT thin films had good ferroelectric properties with high remanent polarizations and strong fatigue resistances. [ABSTRACT FROM AUTHOR]

The formation of phase-pure BiFeO 3 (BFO) thin films using a chemical solution deposition on platinium electrode has been investigated systematically by changing the annealing condition of the films. From the X-ray diffraction results, it was found that the formation of the phase-pure BFO was favorable under lower oxygen partial pressure, slower heating rate and Pt(200)/Ti/SiO 2 /Si(100) substrate. The remanent polarization ( P r ) and coercive field ( E c ) values of the phase-pure BFO thin film annealed at 600°C in nitrogen atmosphere by conventional furnace annealing method are approximately 0.9 μC/cm 2 and 20 kV/cm, respectively. [ABSTRACT FROM AUTHOR]

Lanthanides (La3+, Nd3+, Sm3+ and Eu3+) doped Bi4Ti3O12 (BIT) films fabricated on p-type Si(100) substrates by a sol-gel spin coating process. The films were characterized by X-ray diffractometer and scanning electron microscope. Memory windows calculated from the measured C-V hysteresis curves were approximately 3.5, 0.85, 0.8, and 0.54 V for La-, Nd-, Sm-, and Eu-doped BIT films with a sweep voltage of ± 10 V, respectively. The effects of lanthanides substitution for Bi3+ in the perovskite layer on the electrical properties, such as C-V and I-V characteristics, have been reported. [ABSTRACT FROM AUTHOR]