Thermopolarization Effect Research Articles

Thermo-electro-elastic analysis of piezoelectric hollow cylinder with thermopolarization effect

Thermopolarization effect, refers to the coupling between electric polarization and temperature gradient, represents the linear response of electric polarization to temperature gradient. Although the thermal polarization effect was observed in many experiments, the qualitative and quantitative effects of thermal polarization on solids have not been studied. Thus, to clarify the quantitative impact of thermopolarization effect, based on the linear piezoelectric theory, the fundamental equations of the thermal-piezoelectric dielectric with the thermopolarization effect were derived, and a hollow piezoelectric cylinder was analyzed. The results show that the increasing thermopolarization coefficient can change the radial stress and circumferential stress sign, which is helpful to regulate the stress distribution in the cylinder. Besides, an interesting result shows that the increasing thermopolarization coefficient can shorten the time of the coupling process to the steady state. These results are useful for understanding the basic mechanical and physical properties of the thermo-electro-elastic multi-field coupling of piezoelectric cylinders. It helps to provide useful guidance for the design of microelectronic devices working in harsh environments.

Seebeck Coefficient of Liquid Water from Equilibrium Molecular Dynamics.

The application of a temperature gradient to an extended system generates an electromotive force that induces an electric current in conductors and macroscopic polarization in insulators. The ratio of the electromotive force to the temperature difference, usually referred to as the Seebeck coefficient, is often computed using nonequilibrium techniques, such as nonequilibrium molecular dynamics (NEMD). In this article, we argue that thermo-polarization effects in insulating fluids can be conveniently treated by standard equilibrium thermodynamics and devise a protocol─based on a combination of equilibrium molecular dynamics and Bayesian inference methods─that allows one to compute the Seebeck coefficient in these systems along with a rigorous estimate of the resulting statistical accuracy. The application of our methodology to liquid SPC/E water results in good agreement with previous studies─based on more elaborate NEMD simulations─and in a more reliable estimate of the statistical accuracy of the results.

Temperature-Assisted Piezoresponse Force Microscopy: Probing Local Temperature-Induced Phase Transitions in Ferroics

The combination of local heating and biasing at the tip-surface junction in temperature-assisted piezoresponse force microscopy (TPFM) opens a pathway for probing local temperature-induced phase transitions in ferroics, exploring the temperature dependence of polarization dynamics in ferroelectrics and potentially discovering coupled phenomena driven by strong temperature and electric field gradients. Here, we analyze the signal-formation mechanism in TPFM and explore the interplay between thermal- and bias-induced switching in model ferroelectric materials. We further explore the contributions of the flexoelectric and thermopolarization effects to the local electromechanical response and demonstrate that the latter can be significant for ``soft'' ferroelectrics. These results establish a framework for the quantitative interpretation of TPFM observations, predict the emergence of nontrivial switching and relaxation phenomena driven by nonlocal thermal-gradient-induced polarization switching, and open a pathway for exploring the physics of thermopolarization effects in various noncentrosymmetric and centrosymmetric materials.

Equations of the Local Gradient Electromagnetothermomechanics of Polarizable Nonferromagnetic Bodies with Regard for Electric Quadrupole Moments

We formulate a complete system of relations of the local gradient electromagnetothermomechanics of electrically conductive nonferromagnetic polarizable solid media. The nonlocal character of the constitutive relations of the proposed mathematical model is explained by the presence of electric quadrupole moments in the polarization current. As a result of taking into account these moments, the space of parameters of the thermodynamic state of the body is expanded by including a pair of additional conjugate parameters, namely, the quadrupole moment and the gradient of the vector of electric-field intensity. It is shown that the developed model takes into account the electromechanical interaction for materials with high level of symmetry (isotropic materials) and describes the flexoelectric and thermopolarization effects. We also present the key system of equations for a physically and geometrically linear medium.

Thermopolarization Effect in Linear Polyethylene Oxide upon Crystallization from Melt

The correlation between crystallite structural changes and polarization properties of a linear crystallized [–CH2CH2O–]n polyethylene oxide polymer is studied. The average spherulite radius and polarization of polyethylene oxide are inspected as functions of molecular weight of polymer and crystallization temperature from melt in a nonuniform temperature field.

Thermopolarization Phenomena in the Temperature Range of Glass Transition of Amorphous Polydiethylsiloxane

The transition from the glass to the highly elastic state in polydiethylsiloxane (PDES) is not reflected on the temperature dependences of the relative permittivity, the dielectric loss tangent, and the specific volumetric electrical conductivity. But, the peak of the current of thermostimulated depolarization (TSD) is fixed in the temperature range of the transition to the highly elastic state. The peak of the TSD current at T ~ 130K indicates a continuous amorphous phase formation in the experimental conditions. The maximum value of the TSD current directly depends on the content of the amorphous phase in the polymer. The cooling of the polymer in an electric field reduces the magnitude of the peak. Exposure in the mesophase leads to an almost complete absence of thermopolarization effects near the glass transition temperature. This peak of the TSD current in the absence of preliminary polarization is characteristic, presumably, only for flexible-chain polymers where structural units have pyroelectric properties. Under certain conditions, PDES demonstrates itself as an active dielectric in the temperature range of 90 - 180K.

Effect of Heating on the Subsurface Inhomogeneity of the Electric and Mechanical Fields in Dielectrics

UDC 539.3 The relations of the local gradient theory of dielectrics based on the analysis of the process of local displacements of masses are used for the investigation of the stress-strain state and polarization of a hollow sphere. The surfaces of the sphere are free of force loads and may have different temperatures. It is shown that the relations of this nonlocal theory enable one to estimate the effect of the temperature gradient on the subsurface inhomogeneity of the fields of stresses, polarization, and bound electric charges. These relations also describe the pyroelectric and thermopolarization effects.

Thermopolarization effect in the cavity structures of heterogeneous systems

Studies of the thermopolarization effects in heterogeneous structures not only yields data on the dynamics of supramolecular structure of their components but can also be one way of testing their applicability for solid state energy converters. An analysis of the possibility of using such heterogeneous structures as wood as material for solid state converters is offered, based on a study of electrokinetic phenomena in wood pores.

Water polarization induced by thermal gradients: The extended simple point charge model (SPC/E)

We investigate the non-equilibrium response of extended simple point charge (SPC/E) water to thermal gradients. Using non-equilibrium molecular dynamics simulations, we show that SPC/E water features the thermo-polarization orientation effect, namely, water becomes polarized as a response to a thermal gradient. The polarization field increases linearly with the thermal gradient, in agreement with predictions of non-equilibrium thermodynamics theory. This observation confirms the generality of the thermo-polarization effect, first reported using the Modified Central Force Model (MCFM), and shows this physical effect is present irrespective of the water model details, in particular, dipole moment magnitude and model flexibility. The magnitude of the effect is the same for both models, although the sign of the electrostatic field is reversed in going from the MCFM to the SPC/E model. We further analyze the impact that the molecular geometry and mass distribution has on the magnitude of the polarization. Our results indicate that the thermo-polarization effect should be observed in a wide range of polar fluids, including fluids where hydrogen bonding is not present. Using various molecular models, we show that the polarization of these fluids under appropriate thermodynamic conditions can be of the same order or stronger than in water.

Laser Intensity Modulation Method and Thermal Gradient Induced Polarization

The contribution of thermopolarization effect (P ∼ grad T) to the signal detected by laser intensity modulation method (LIMM) was studied theoretically. It was shown that this contribution is large enough to be observable. The properties of thermopolarization and pyroelectric signals are compared.

Reverse thermopolarization effects in dielectrics

Abstract The reverse thermopolarization effect in dielectrics manifested by a appearance of a temperature difference δ between the opposite sides of charging and discharging capacitors was observed. A capacitor of PbMg1/3Nb2/3O3 (PMN) crystals was charged by applying an electric field of E = 106V/m with a time constant. ≃ 10−5s. The temperature difference δ amounted ≃ 10−4K at 293 K. The thermal and electric field dependencies of this effect were investigated too. The analysis of the generalized Peltier effect at the boundary of two arbitrary materials shows that the experimental results can be considered as a “dielectric Peltier effect”.

Effects of thermally induced birefringence in high-output-power electro-optically Q-switched Nd:YAG lasers and their compensation

We show that thermally induced birefringence in an electro-optical crystal can play an important role in Q-switched Nd:YAG lasers with a high average power output. A compensation of the thermal effects in both active-element and electro-optical crystals is achieved by employing two identical Pockels cells instead of one, with a pi/2 polarization rotator between them in the so-called ring modulator. Experiments that are carried out show that undesirable thermopolarization effects are essentially eliminated by using this new optical configuration. A detailed description in terms of Jones matrices of the properties of the proposed resonator is also included.

Electric polarization in crystals and its response to thermal and elastic perturbations

Abstract The basic properties of electric polarization response in crystalline dielectrics are theoretically analysed. Spontaneous polarization, pyroelectricity, piezoelectricity, flexoelectricity (polarization response to strain gradient) and thermopolarization effect (polarization response to temperature gradient) are discussed on the basis of a unified approach. Special attention is paid to the problem of the adequate theoretical definition of these phenomena. The effect of the sample termination on the polarization response is considered in detail.

Recent developments of the thermopolarization effect investigation

Abstract The last results of the thermopolarization effect investigation are described. Thermopolarization effect in both, centrasymmetric (SrTiO3, KTaO3) and piezoelectric (KH2PO4) single crystals have been discovered in spite of the tertiary pyroeffect competition. The main criteria of thermopolarization and tertiary pyroeffect and experimental evidence of “proper'’ (nonflexoelectrical in nature) thermopolarization effect existence are obtained.

Dielectric relaxation and the thermopolarization effect in crystals

Dielectric relaxation and the thermopolarization effect in crystals

Dielektricheskaya relaksatsiya i termopolyarizatsionnyi effekt v kristallakh

Dielektricheskaya relaksatsiya i termopolyarizatsionnyi effekt v kristallakh