Value Of Pyroelectric Coefficient Research Articles

A study of the electrophysical parameters of some solid solutions of the Pb0.88Ba0.08Sr0.04TixZr1-xO3 system

The present paper deals with a study of the effect of replacement of Pb2+ ions by Ba2+ and Sr2+ ions in a discrete series Pb0.88 Ba0.08Sr0.04TixZr1-xO3 with 0.2 < x < 0.55. X-ray studies were carried out. The temperature dependencies of the pyroelectric coefficient in a dynamic regime, the capacitance and the conductivity were determined. The additional maxima corresponding to the isostructural transition from a low temperature rhombohedral to a high-temperature phase were obtained on the temperature curve of the pyroelectric coefficient. Of particular interest is the composition with the PbTiO<sb>3 content of 0.34 mol% having the high value of pyroelectric coefficient d(Troom)∼ 7 × 104 C/(m2 × K).

Grain-oriented surface crystallization of lanthanum borosilicate and lanthanum borogermanate glasses

Under appropriate conditions (high temperature gradient, rapid heating and following prolonged isothermal treatment, suppression of bulk crystallization, polished glass surface, etc.) the La 2O 3-B 2O 3- XO 2 ( X = Si, Ge) systems glasses are crystallized in preference on the surface with formation of perfect textures based on needle-shaped stillwellite-like crystals of the LaBXO 5 composition. Lanthanum borogermanate (LBG) glasses exhibit more intense texture-forming ability than lanthanum borosilicate (LBS) ones. Glass ceramic textures with a degree of grain orientation up to 0.9 in the LBG system are obtained. The pyroelectric coefficient values of the best of synthesized LBG textures are as high as 0.5–1.5 nC cm −2 K −1 in a wide temperature range. A poor crystallization ability of the LBS glasses at temperatures less than 1000°C supposed to be used in preparing both thin polar crystalline films on the glass surface for nonlinear optical applications and ferroelectric (pyroelectric) glass ceramics by the powder technology.

Electroactive properties of polymer-ceramic composites

Abstract The nature of absorption and steady state electrical conduction as well as the dielectric and pyroelectric behaviour have been studied for polymer/ceramic composites. Experimentally observed values of pyroelectric coefficient and dielectric permittivity for various PZT content of PZT/PVDF composites seem to agree well with the calculated values. A high dielectric permittivity of polymer coupled with high pyroelectric activity of PZT may contribute to the high pyroelectric coefficient in the PZT/PVDF composites. The dielectric loss processes of the polymer-ceramic composites are observed to be dominated by those of the polymer whereas the ceramic phase may contribute significantly to the steady state electrical conduction which is suggested to be of ionic origin.

Chirality Induced Pyroelectricity in the Liquid Crystal p-DiMethylAminoBenzaldehyde

Films of p-DiMethylAminoBenzaldehyde exhibit pyroelectricity in the temperature range 58° to 77°C and indicates the presence of a phase with spontaneous polarization. The origin of pyrocurrent can be attributed to the reorientation of two dipole groups CHO and (CH3)2N around the long molecular axis. The high value of pyroelectric coefficient 6.8×10-8 C/cm2/°C around 63°C showing a maxima, is thought to be due to the combined effect of the reorientation of these two dipole moments. The molecular contribution from the CHO group is expected to be larger here and has more temperature dependence.

Dielectric Properties of Ceramic Lead Germanate Derivatives

Dielectric properties of Pb5-xAxGe3-yByO11 (A=Ca, Sr, Ba, Bi, La, Bi–Ag; B=Si, Ti, Zr, Hf, Mg-W or Al–Nb) have been investigated for an application to a pyroelectric detector. The ceramics substituted by Sr and Ba for Pb site and by Si for Ge site showed higher values of pyroelectric coefficient than the pure lead germanate (abbreviated to PGO here) ceramic. However, taking into account the values of Curie temperature, Ba- and Sr-substituted ceramics (PBGO and PSGO, respectively) are quite useful. At room temperature, the figures of merit of the PBGO with x=0.05 and the PSGO with x=0.025∼0.075 are comparable to that of the PGO single crystal. The pyroelectric coefficient of the PSGO with x=0.05 measured directly is 7.4 nC/K·cm2, which is larger than that evaluated from a Ps-value obtained from D–E hystrisis loop, assuming a second order transition.

Pyroelectric properties and the nature of the polarization of polyacrylonitrile

The pyroelectric peroperties and the nature of the polarization of PAN have been investigated. The polarization that gives rise to the pyroelectric properties is caused by the “freezing in” of oriented dipole groups during cooling to room temperature in an electric field. The pyroelectric current is determined by the rotation of these dipoles around an equilibrium position as the temperature is changed. The maximum value of the pyroelectric coefficient, P, is equal to 3·9 × 10 −9 coulomb/cm 2·deg K. The production of electret films of large area and having a high value of pyroelectric coefficient makes it possible to put forward the question of using them as elements for the direct transformation of solar energy into electrical energy.

Reversible domain switching in ferroelectric triglycine sulphate (TGS) by Laser

It is known1 that laser pulses can lead to reversible domain switching in ferroelectric TGS. A tentative explanation in terms of a depolarizing electric field issued from bound charges due to thermal shock was proposed.2Experiments are now given showing that a slow quasistatic illumination leads to the same reversible domain switching. In this case the electric field inside the crystal is easier to calculate. In a rough approximation assuming known values of pyroelectric coefficient, thermal conductivity and dielectric constant, it is shown that close to the surface the electric field is parallel to the spontaneous polarization. Inside the crystal it is opposed to it with values of the same order of magnitude as the coercive field at room temperature measured by classical methods. It is thus demonstrated that such a field is really responsible for the domain switching.The pyroelectric probe technique is used to inspect the surface opposite to a fixed illuminating spot and has shown the end of a domain whi...

A new method of measuring pyroelectric coefficients

A method of measuring the pyroelectric coefficient of a dielectric is described. The method employs sinusoidal variations of sample temperature by an accurately known amount at frequencies in the range 0.01-1 Hz. Under properly chosen conditions the pyroelectric voltage produced does not depend on any other parameter of the material under test. Absolute values of pyroelectric coefficient may be measured, with reasonable care, to within +or-5% at spot temperatures in the range 200-350K. The results are easily and quickly obtained from chart recordings. The method is illustrated with reference to two well known pyroelectric materials, triglycine sulphate and lithium sulphate.