Depolarization of multidomain ferroelectric materials

Depolarization in ferroelectric materials has been studied since the 1970s, albeit quasi-statically. The dynamics are described by the empirical Merz law, which gives the polarization switching time as a function of electric field, normalized to the so-called activation field. The Merz law has been used for decades; its origin as domain-wall depinning has recently been corroborated by molecular dynamics simulations. Here we experimentally investigate domain-wall depinning by measuring the dynamics of depolarization. We find that the boundary between thermodynamically stable and depolarizing regimes can be described by a single constant, Pr/ε0εferroEc. Among different multidomain ferroelectric materials the values of coercive field, Ec, dielectric constant, εferro, and remanent polarization, Pr, vary by orders of magnitude; the value for Pr/ε0εferroEc however is comparable, about 15. Using this extracted universal value, we show that the depolarization field is similar to the activation field, which corresponds to the transition from creep to domain-wall flow.Aerospace Structures & MaterialsNovel Aerospace Material

Dielectric and electromechanical properties of ferroelectric-relaxor 0.9 Pb(Mg1/3Nb2/3)O-3-0.1PbTiO(3) thin films

Pyrochlore free 0.9Pb(Mg1/3Nb2/3)O-3-0.1PbTiO(3) thin films were prepared from alkoxide-based solution precursors. Preferential (111) crystallographic orientation was obtained on TiO2/Pt/TiO2/SiO2/Si substrates by spin coating. Dielectric, electrostrictive, and piezoelectric properties of the films were characterized in detail. Films show relaxor-like behavior, but with dielectric permittivity which is low (around 4300 at peak and at 340 Hz with E-ac=1.6x10(6) V/m) compared to bulk ceramics and single crystals. Several parameters which might be responsible for this lower permittivity are suggested. The ac and dc field dependences of the dielectric response have been investigated. Electrostrictive coefficients, M-11(7.76x10(-18) m(2)/V-2) and Q(11)(1.9x10(-2) m(4) C-2), were determined by measuring strain and polarization as a function of the electric field (E-ac). The maximum field induced piezoelectric d(33) coefficient is 100 pm/V and electrostrictive strains up to 1.2x10(-3) (with an ac electric field of 140 kV/cm) were measured. (C) 2001 American Institute of Physics

Electromechanical properties and self polarization in relaxor Pb(Mg1/3Nb2/3)O-3 thin films (vol 89, pg 1393, 2001)

Pyrochlore free Pb(Mg1/3Nb2/3)O-3 (PMN) thin films were prepared from alkoxide-based solution precursors. The influence of different seeding layers and chemical solution on the microstructures is shown. Dielectric, electrostrictive, and piezoelectric properties of the films were characterized in detail. Films show relaxor-like behavior, but with dielectric permittivity which is low (around 4000 at peak) compared to bulk ceramics and single crystals. Several parameters which might be responsible for this lower permittivity are suggested. Electrostrictive coefficients, M and Q, were determined by measuring strain S and polarization P as a function of the electric field (E-ac). At large fields (>2.6x10(6) V/m), S vs P-2 appears to deviate from linear behavior possibly suggesting that the electrostrictive coefficient Q becomes nonlinear in this field range. Investigated as-prepared PMN films exhibit piezoelectric response in the absence of a dc electric field (d(33)=8-20 pm/V). The value of the associated self-polarization in the films is estimated and its presence confirmed by zero-field pyroelectric measurements. The self-polarization and the piezoelectric coefficient are strong functions of the ac field amplitude. Asymmetry of S vs E-ac and d(33) vs E-dc loops are related to the self-polarization. An ac field induces shift in P vs E loops along the field axis. This increase in the coercive field is associated, through a simple model, with the presence of the self-polarization. (C) 2001 American Institute of Physics

Properties of ferroelectric PbTiO3 thin films

PbTiO3 thin films were prepared from alkoxide solution precursors and crystallized onto Pt/TiO2/SiO2/Si substrates. Microscopy observations revealed that the complexity of the domain walls structure decreased with the grain size. Dielectric, electrostrictive, and piezoelectric properties of the films were characterized in details. A shift of the temperature of the dielectric permittivity maximum due to stresses in the plane of films has been observed. Electrostrictive M and Q coefficients were estimated by measuring strain as a function of the ac electric field amplitude. The d(33) vs E-dc loops are rectangular with a maximum weak field piezoelectric d(33) coefficient equal to 65 pm/V. The dielectric permittivity and piezoelectric nonlinearities can be explained by taking into account domain-walls contributions. Dielectric and piezoelectric aging was investigated. It was found that both coefficients follow logarithmic time dependence, with comparable rates. The aging behavior in the PT films is thus qualitatively closer to that in ceramics than in thin films of lead zirconate titanate.(C) 2002 American Institute of Physics

Preparation and electromechanical properties of Pb(Mg1/3Nb2/3)O-3 thin film

Pb(Mg1/3Nb2/3)O-3 (PMN) alkoxide precursor solutions were synthesized and used to prepare thin layers on TiO2/Pt/TiO2/SiO2/Si substrates by spin coating. Many parameters like homogeneity of the solution and appropriate processing must be controlled to minimize the pyrochlore formation. Optimization of the processing allowed highly (111)-oriented thin films to be obtained. Dielectric measurements and TEM investigations were performed and showed that PMN thin films exhibit relaxer behavior

Relaxor behavior and electromechanical properties of Pb(Mg1/3Nb2/3)O-3 thin films

Pb(Mg1/3Nb2/3)O-3 (PMN) alkoxide precursor solutions were synthesized and used to prepare thin films by spin coating on TiO2/Pt/TiO2/SiO2/Si substrates. Many parameters like the use of homogeneous and stable precursor solutions and appropriate processing were used to greatly reduce the presence of the nonferroelectric pyrochlore phase. Transmission electron microscopy investigations, dielectric, electrostrictive, and direct current field induced piezoelectric measurements were carried out and have shown that PMN thin films exhibit a relaxor-like behavior. (C) 1998 American Institute of Physics. [S0003-6951(98)03142-8]

Relaxor Pb(Mg1/3Nb2/3)O-3 thin films and their electromechanical properties

Pb(Mg1/3Nb2/3)O-3 thin films were prepared from modified alkoxide solution precursors and their dielectric and electromechanical characteristics were investigated. Preparation of the films is very sensitive to processing parameters. The influence of different seeding layers on the microstructures is discussed. Films show relaxer-like behavior, but with dielectric permittivity which is low (4500 at peak) compared to bulk ceramics and single crystals. Large electric de bias fields (up to 120 kV/cm) can be applied to the films. This de field reduces the permittivity, suppresses the frequency dispersion and flattens the permittivity-peak. No anomaly in temperature dependence of the permittivity associated with the held induced transition into, a ferroelectric phase was observed. The maximum field induced piezoelectric d(33) coefficient is around 85 pm/V and electrostrictive strains up to 1.6 10(-3) were measured with an electric field of 30 kV/cm

New sol-gel route for processing of PMN thin films

Pyrochlore free Pb(Mg1/3Nb2/3)O-3 (PMN) thin films were prepared from mixed-metal precursors solutions using the sol-gel process. Lead acetate [Pb(CH3COO)(2)], magnesium acetate [Mg(CH3COO)(2)] and niobium ethoxide [Nb(C2H5O)5] were used as starting materials, while 2-isopropoxy-ethanol was chosen as solvent. The reactivity of the precursors was investigated in order to understand and control the process and thus to prevent the contamination of the PMN with the pyrochlore phase. The solution was spin-coated on TiO2/Pt/TiO2/SiO2/Si substrate. The thin films were characterized by SEM and XRD while dielectric measurements were performed on the bulk ceramic

Insights in the sol-gel processing of Pb(Mg1/3Nb2/3)O-3. The synthesis and crown structure of a new lead magnesium cluster: Pb6Mg12(mu-OAc)(6)( mu(2), eta(2)-OAc)(18)(mu(3), eta(2)-OC2H4OPri)(12)

The synthesis and molecular structure of a Pb-Mg bimetallic acetatoalkoxide (Pb-6,Mg-12( mu-OAc)(6)(mu(2), eta(2)-OAc)(18)(mu(3), eta(2)-OC2H4OPr1)(12), space group R-3, a = b = 30.032(2), c = 18.855(2) Angstrom, alpha = beta = 90degrees, gamma = 120degrees) are discussed in this article. This compound was isolated as an intermediate during the elaboration of Pb(Mg1/3Nb2/3)O-3 (PMN) using sol-gel process. It results from the reaction of a bimetallic Mg/Nb species with lead acetate in 2-isopropoxyethanol. (C) 2002 Elsevier Science B.V. All rights reserved