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15 Sep 2005

Volume 98, Issue 6, Articles (06xxxx)

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A phenomenological thermodynamic potential for BaTiO3 single crystals

Y. L. Li, L. E. Cross, and L. Q. Chen

J. Appl. Phys. 98, 064101 (2005); http://dx.doi.org/10.1063/1.2042528 (4 pages) | Cited 74 times

Online Publication Date: 16 September 2005

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A phenomenological thermodynamic potential was constructed based on the properties of bulk BaTiO3 single crystals. An eighth-order polynomial of Landau-Devonshire expansion was employed. It reproduces bulk properties including the three possible ferroelectric transition temperatures and their dependence on electric fields, as well as the dielectric and piezoelectric constants. Different from the existing thermodynamic potential, it is applicable to predicting the ferroelectric phase transitions and properties of BaTiO3 thin films under large compressive biaxial strains.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
65.40.G- Other thermodynamical quantities
77.55.-g Dielectric thin films
77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
77.22.Ch Permittivity (dielectric function)
77.65.Bn Piezoelectric and electrostrictive constants

Nonlinear dynamics of piezoelectric high displacement actuators in cantilever mode

Tim Usher and Alec Sim

J. Appl. Phys. 98, 064102 (2005); http://dx.doi.org/10.1063/1.2041844 (7 pages) | Cited 10 times

Online Publication Date: 19 September 2005

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Experimental results of the nonlinear dynamic response of a piezoelectric high displacement actuator known as thin-layer composite unimorph ferroelectric driver and sensor were compared to a theoretical model, which utilizes the multiple scales method to connect the effective spring constant to higher-order stiffness constants c4 of the piezoelectric layer. This type of actuator has prestress gradients resulting from the manufacturing process that have been reported to play an important role in enhanced actuation. A value of c4 = −4.7×1020 N/m2 was obtained for the higher-order lead zirconate titanate (PZT) stiffness coefficient, which is higher than other published results for PZT without prestress gradients. Peak resonance displacements over 1 mm were obtained for even small (100 Vpp) applied fields. The analysis showed a slight voltage dependence that was not specifically accounted for in the theory. This was confirmed by recasting data from other published results and further confirmed by dc offset studies reported here.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Dielectric properties of Sb2O3-doped BaFe12O19 ferrite

P. Brahma, S. Banerjee, and D. Chakravorty

J. Appl. Phys. 98, 064103 (2005); http://dx.doi.org/10.1063/1.2058220 (5 pages) | Cited 1 time

Online Publication Date: 26 September 2005

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Dielectric measurements were carried out on specimens with compositions BaO.(6−x)Fe2O3.x Sb2O3 with x having values of 0.0, 0.025, 0.1, and 0.3. Sb2O3 doping increases the dielectric permittivity drastically. Two loss peaks of similar activation energies were observed. The analysis showed that these arose because of the presence of Fe2+–Fe3+ and Sb3+–Sb5+ pairs, respectively, in the system. The experimental data could be analyzed satisfactorily in terms of Cole-Cole relaxation formalism. The relaxation distribution parameter α was found to be much larger in the case of Sb3+–Sb5+ pair than that due to Fe2+–Fe3+ pair.
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77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Ultraviolet light-assisted domain inversion in magnesium-doped lithium niobate crystals

M. C. Wengler, U. Heinemeyer, E. Soergel, and K. Buse

J. Appl. Phys. 98, 064104 (2005); http://dx.doi.org/10.1063/1.2058184 (7 pages) | Cited 22 times

Online Publication Date: 26 September 2005

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The influence of ultraviolet (UV) light (wavelengths λ = 334 and 305 nm) on the ferroelectric domain inversion of lithium niobate crystals doped with different amounts of magnesium ranging from 0 to 7.5 mol % is investigated. Illumination at λ = 334 nm leads to a coercive field reduction of up to 50%, but only in samples doped with a magnesium concentration above the so-called optical damage threshold. For λ = 305 nm the effective coercive field is reduced significantly in all samples. Different behavior of the coercive field reduction at both wavelengths indicates the presence of two mechanisms. To explain the effect occurring for 305 nm illumination a model is presented in which an UV-induced photoconductivity alters the electric-field distribution through the crystal thickness. Utilizing an UV-interference pattern and a suitable homogeneous external electrical field, periodically poled lithium niobate with a period length of 55 μm is produced.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
72.80.Sk Insulators
72.40.+w Photoconduction and photovoltaic effects

Verification of a model for the piezoelectric d33 coefficient of cellular electret films

Joachim Hillenbrand, Gerhard M. Sessler, and Xiaoqing Zhang

J. Appl. Phys. 98, 064105 (2005); http://dx.doi.org/10.1063/1.2058185 (5 pages) | Cited 21 times

Online Publication Date: 26 September 2005

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An existing model for the piezoelectric thickness coefficient (d33 coefficient) of cellular polymers is tested with experimental data obtained from two differently manufactured cellular polypropylene (PP) materials. The model assumes the cellular film to consist of plane parallel solid and gaseous layers charged at their interfaces. The cellular PP films are expanded by a pressure treatment. Subsequently, due to viscoelastic relaxation, the thickness of the films decreases, thus causing a change of their Young’s modulus Y with time. The values of Y are obtained from interferometric measurements of the resonance frequency of the films. Together with the measured thickness of the solid layers and air layers in the material, the d33 coefficients can be determined from the model. These values are compared with experimental results for d33 also obtained interferometrically by means of the inverse piezoelectric effect. A very good agreement between the measured and calculated d33 coefficients as a function of film thickness is obtained for all investigated films.
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77.84.Jd Polymers; organic compounds
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Ej Polarization and depolarization
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
62.20.D- Elasticity

Hysteresis dispersion scaling of a two-dimensional ferroelectric model

L.-F. Wang and J.-M. Liu

J. Appl. Phys. 98, 064106 (2005); http://dx.doi.org/10.1063/1.2058168 (5 pages) | Cited 2 times

Online Publication Date: 27 September 2005

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The ferroelectric hysteresis dispersion of a two-dimensional ferroelectric model lattice in an ac electric field of amplitude E0 and frequency ω over a wide range, respectively, is calculated by Monte Carlo simulation based on the Ginzburg-Landau theory on tetragonal-type ferroelectric phase transitions. Given a fixed field amplitude E0, the hysteresis dispersion as a function of field frequency ω shows a single-peaked pattern, which predicts the existence of a characteristic time responsible for domain switching in an external electric field. The scaling analysis demonstrates that given different field amplitudes E0, the hysteresis dispersions can be scaled and the characteristic time depends inversely on the field amplitude E0 over a wide range of E0, but the large deviation occurs as E0 is very small or extremely large.
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77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point
77.80.Fm Switching phenomena

Dielectric properties of Ba0.6Sr0.4TiO3/Mg2SiO4/MgO composite ceramics

Ying Chen, Xian-Lin Dong, Rui-Hong Liang, Jian-Tong Li, and Yong-Ling Wang

J. Appl. Phys. 98, 064107 (2005); http://dx.doi.org/10.1063/1.2058194 (5 pages) | Cited 48 times

Online Publication Date: 28 September 2005

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The dielectric properties of BSTO/Mg2SiO4/MgO composite ceramics have been investigated systematically. The dielectric properties of BSTO composites under a dc bias field can be interpreted by the “soft-mode” theory near the phase transition and Johnson’s phenomenological equation far above the transition temperature. Compared with most of the other BSTO composite ceramics, BSTO/Mg2SiO4/MgO not only can be sintered at a lower temperature but also keep a higher dielectric tunability versus a lower dielectric constant. For example, BSTO/35 wt. %Mg2SiO4/15 wt. %MgO has a dielectric tunability ∼ 13.18% (under 2 kV/mm biasing) versus a dielectric constant εr(0) ∼ 118.40 at 25 °C. It suggests that the dielectric properties are influenced to a great extent by the microstructure, and the dielectric tunability is enhanced when more continuous BSTO phase is obtained.
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77.84.Lf Composite materials
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)

Microstructure and ferroelectric properties of MnO2-doped bismuth-layer (Ca,Sr)Bi4Ti4O15 ceramics

Gurong Li, Liaoying Zheng, Qingrui Yin, Bei Jiang, and Wenwu Cao

J. Appl. Phys. 98, 064108 (2005); http://dx.doi.org/10.1063/1.2058174 (7 pages) | Cited 39 times

Online Publication Date: 29 September 2005

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We have studied the microstructures and ferroelectric properties of MnO2-doped bismuth-layered (Ca,Sr)Bi4Ti4O15 (CSBTM). The piezoelectric coefficient, dielectric loss, mechanical quality factor, and the P-E hysteresis loop measurements indicate that Mn ions entered both the A and B sites of the pseudoperovskite-layered structure, creating “soft” and “hard” doping effects simultaneously. Scanning electron microscopy and energy dispersion spectroscopy showed that the platelike grains in CSBTM ceramics become larger with the increase of MnO2 additive, and Mn ions are found inside the grains as well as in the grain boundaries. The lattice parameter, room-temperature dielectric constant, and the Curie temperature do not vary with MnO2 additive. We conclude that the Mn3+ ions play a critical role in the effects of soft and hard behaviors since it can enter both the A and B sites of the perovskite structure.
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77.80.B- Phase transitions and Curie point
77.80.Dj Domain structure; hysteresis
61.72.Mm Grain and twin boundaries
61.66.Fn Inorganic compounds
77.65.Bn Piezoelectric and electrostrictive constants
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)

All-epitaxial growth of Ba0.6Sr0.4(Ti0.94Al0.06)O3–Si heterostructures and their leakage current characteristics

Tong Lai Chen, Xiao Min Li, and Wen Biao Wu

J. Appl. Phys. 98, 064109 (2005); http://dx.doi.org/10.1063/1.2060960 (4 pages)

Online Publication Date: 30 September 2005

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6 at. % Al-doped Ba0.6Sr0.4TiO3 (BSTA) thin films were grown on Ir/MgO-buffered Si(001) substrates by in situ pulsed-laser deposition techniques. All-epitaxial growth of BSTA/Ir/MgO/Si(001) heterostructures with layer-by-layer mode was evidenced by in situ reflection high-energy electron-diffraction observation and x-ray diffraction. The epitaxy relationship was determined as: BSTA〈100〉‖Ir〈100〉MgO〈100〉‖Si〈100〉 (in-plane) and BSTA(001)‖Ir(001)MgO(001)‖Si(001) (out-of-plane). The BSTA thin films exhibit an extremely smooth surface with a roughness of RMS = 0.89 nm. The largely reduced leakage current for BSTA thin films, which was dominated by the Schottky emission mechanism, might be attributed to combination effects of the crystal-structure-perfection and acceptor Al doping. Moreover, the BSTA thin films show good dielectric properties at low-frequency regime.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
61.72.up Other materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.30.+y Surface double layers, Schottky barriers, and work functions
61.66.Fn Inorganic compounds
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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