Pyroelectric Polyvinylidene Fluoride Research Articles

Pyroelectric polyvinylidene fluoride film prepared by a novel combining method and its application in fully flexible infrared detector

For the fabrication of pyroelectric polyvinylidene fluoride (PVDF) film with high performance, a novel method is presented which combines the usual two steps of solution casting and stretching into one. It demonstrates that a stretch ratio as large as 15 as well as low quantity of defects and high uniformity are achieved by this new technique. The characterization results reveal that baking temperature (Tb) after stretching has significant and similar influences on relative β-phase fraction (Fβ), remnant polarization (Pr), dielectric constant and loss (ε′ and ε″) and pyroelectric coefficient of the samples; the highest pyroelectric coefficient, occurring at baking temperature of 80 °C without thermal poling, is 12.4μCm−2K−1, which is larger than that of the usually-stretched sample undergoing thermal poling. In addition, by using the prepared film as sensitive element, a novel chopperless pyroelectric infrared detector is constructed by electrostatically modulating the incident thermal irradiation; the measurement results demonstrate that the detector has excellent pyroelectric voltage response to the thermal radiation of the laser source and hot (warm) water with a sensitivity of 2.65 × 104V/W, showing its good potential for fully flexible infrared detector and temperature sensor.

Multicaloric effect in a multiferroic composite of Gd5(Si,Ge)4 microparticles embedded into a ferroelectric PVDF matrix

The coupling between electric, magnetic and elastic features in multiferroic materials is an emerging field in materials science, with important applications on alternative solid-state cooling technologies, energy harvesting and sensors/actuators. In this direction, we developed a thorough investigation of a multiferroic composite, comprising magnetocaloric/magnetostrictive Gd{}_{5}Si{}_{2.4}Ge{}_{1.6} microparticles blended into a piezo- and pyroelectric poly(vinylidene) fluoride (PVDF) matrix. Using a simple solvent casting technique, the formation and stabilization of PVDF electroactive phases are improved when the filler content increases from 2 to 12 weight fraction (wt.%). This effect greatly contributes to the magnetoelectric (ME) coupling, with the ME coefficient {alpha }_{ME} increasing from 0.3 V/cm.Oe to 2.2 V/cm.Oe, by increasing the amount of magnetic material. In addition, magnetic measurements revealed that the ME-coupling has influenced the magnetocaloric effect via a contribution from the electroactive polymer and hence leading to a multicaloric effect. These results contribute to the development of multifunctional systems for novel technologies.

Modeling and Simulation for PVDF-based Pyroelectric Energy Harvester

Energy harvesting technology allows the capturing of unused ambient energy such as solar, wind, thermal, strain and kinetic, energy of gas and liquid flows which is then converted into another form of usable energy. This paper focuses on the thermal-electrical energy harvesting based on pyroelectric effect. Pyroelectric materials generate a voltage, when subjected temperature variation. The pyroelectric polyvinylidene fluoride (PVDF) films were fabricated and characterized for pyroelectric and dielectric parameters. Using the foregoing parameters, the energy-harvesting capacity has been theoretically explored by capturing thermal energy available in the environment of Huntsville (pavement), Saudi Arabia (ambient) and MARS (ambient). The predicted maximum cumulative voltage by the end of a 300 hours cycle is approximately 0.13, 0.7 and 7.7 volts for Huntsville and Saudi Arabia and MARS, respectively for the PVDF based 10 cm2 pyro-elements. The results indicate that the electrical energy harvesting via pyroelectricity holds promise for powering autonomous low-duty electric devices. Furthermore, the mathematical modeling and numerical simulations can be helpful in designing of pyroelectric micro-power generators.

Phase transformation and thermomechanical characteristics of stretched polyvinylidene fluoride

Phase transformation and thermomechanical characteristics of the polyvinylidene fluoride (PVDF) are investigated using a microtesting machine and a thermomechanical analyzer. The phase transformation from the α- to β-phase of the PVDF resulted from increased PVDF chain length caused by the stretching procedure. The results show that the phase transformation changed due to increased stretching ratios with smaller changes for stretching ratios over 4. Young's modulus along the stretching direction was higher than that along the transverse of stretching. The thermomechanical curve variation can be divided into two parts: one part is a gradual slope before about 50 °C, and the other is similar to exponential growth. Thermomechanical change, thermal elongation, and expansion greatly influence the stretching ratios of 5 in the stretching direction. The higher stretching ratio easily causes the shrink influence of the material due to the higher cohesion of the amorphous regions. Therefore, the observed results can provide useful information to optimize for piezoelectric or pyroelectric PVDF applications.

Low-noise charge sensitive readout for pyroelectric sensor arrays using PVDF thin film

The paper presents a fully integrated low-noise readout circuit for the purpose of front-end amplification in pyroelectric infrared focal plane arrays (IRFPA). A low-noise and low-power charge sensitive amplifier (CSA) has been fabricated and characterised in a standard CMOS process. A value of 11.4 nV/√Hz at 100 Hz input referred noise voltage has been measured for a maximum power dissipation of 210 μW. Pyroelectric polyvinylidene fluoride (PVDF) thin films have been coated on 256-element focal plane arrays including the low-noise CSA as readout device. Experimental values of voltage responsivities of 3510 V/W on average at 10 Hz modulation frequency have been achieved for a sensing area of 105×105 μm.

Thin nickel films as absorbers in pyroelectric sensor arrays

During the evaporation of nickel on quartz, the square resistance and the IR-transmittance have been investigated simultaneously. A modified Namba model is introduced to explain the measured thickness dependence of resistivity. Inferences on the film growth and the percolation threshold are obtained, which are both important with respect to the absorber quality and fabrication. Thin nickel films of various thicknesses have been deposited on pyroelectric polyvinylidene fluoride (PVDF) films. The transmittance of these two-layer-systems has been measured in the infrared spectral range 2 μm – 50 μm and is compared with theoretical simulations. The absorber characteristic can be varied by an appropriate selection of the thickness of the nickel film. This allows the realization of broadband absorber and of selective absorbers as well. PVDF films coated with optimized nickel absorbers have been used in integrated pyroelectric sensors.

A sensor array for human-body detection based on pyroelectric polyvinylidene fluoride

The pyroelectric polymer polyvinylidene fluoride (PVDF) is particularly suitable for sensor arrays because of its low lateral heat flow. Sensor arrays can be used to determine the direction and, knowing the distance between detector and heat source, the velocity of a heat source. An IR detector based on PVDF is presented in which a sensor array is combined with a suitable optical unit and an amplifier circuit to form a single, complete device. There are a large number of applications such as human body detection, automatic actuation of devices in installations, security, and control engineering. >

Production of Ferroelectric Oriented Pvdf Films

Piezoelectric and pyroelectric polyvinylidene fluoride (PVDF) films and coatings are currently being produced on a commercial basis in the United States, Europe, and Japan. PVDF is the resin of choice due to its high polarizability and ease of pro cessing. The resultant electro-activity depends on the orientation of the crystalline and amorphous regions of the polymer film, the amount of crystallinity, and the extent of dipole orientation.

Thermal diffusivity measurements of thin films with a pyroelectric calorimeter

The use of pyroelectric polyvinylidene fluoride calorimeters for the measurement of thermal diffusivities of thin films is described. The potential of this detection scheme combined with photothermal excitation is demonstrated on polymer films with thickness in the 1 μm range.

Pyroelectric sensing station for automatic recognition of position and orientation of objects

An object position and orientation recognizing device using pyroelectric polyvinylidene fluoride (PVF 2) 16 × 16 sensor matrix is proposed in this paper. A theoretical analysis, based on a three layer sensor model (absorber-pyroelectric film-substrate), of the response of such substrated sensor to rectangular pulse thermal radiation is presented along with its experimental validation. The electronic part and the recognition operation are also briefly described. Satisfactory recognition results have been obtained from a prototype of the proposed device.