Ferroelectric polarization distribution in the sample is measured

Ferroelectric materials possess pyroelectric properties and spontaneous polarisation. All ferroelectric materials are pyroelectric, however, not all pyroelectric materials are ferroelectric. Below a transition temperature called the Curie temperature ferroelectric and pyroelectric materials are polar and possess a spontaneous polarization or electric dipole moment. Inhomogeneous polarization is the typical property of ferroelectric materials, particularly at the surface region. Different mechanisms can cause decrease of polarization near the surface.1Example: High electric fieldsStructural variation of the sample near the surfaceApplications for Ferroelectric Materials:Capacitors, Non-volatile memory, Piezo electrics for ultrasound imaging and actuators, Electro-optic materials for data storage applications, Thermistors, Switches, Oscillators and filters, Light deflectors, modulators and display.Here we are working on PVDF and P (VDF-TrFE) materials. The used P (VDF-TrFE) compositions are P (VDF-TrFE) 56/44 mol% and P (VDF-TrFE) 70/30 mol%. Bi and multilayer films of P (VDF-TrFE) and PVDF are produced and measured the polarization distributions using LIMM method.To measure the charge and polarization distributions, various experimental techniques are available, which are based on the piezoelectric or on the pyroelectric effect. Pyroelectric effect methods are implemented in the time or in the frequency domain. The time domain is the thermal pulse method, while the LIMM uses thermal waves in the frequency domain. Thermal methods are good enough to achieve high resolution near the sample surface. With LIMM we can achieve 0.5?m resolution. The results of polarization investigations in bi and multilayer samples of PVDF and P (VDF-TrFE) are presented.2Charge and polarization distribution in the sample is measured based on the pyroelectric response to a non uniform variation of temperature. Sample is prepared in the form of round shape and the film is covered with electrodes on both sides of surface. Laser light is focused on one side of the surface of the film and that surface gets heated due to absorption of laser light. Heat goes inside the sample through the surface it causes change in the temperature inside the sample.1For the Measurement of pyroelectric current a current to voltage converter, lock in amplifier has been used in computer controlled equipment. The pyroelectric specimen and the reference photo diode both are connected to the input of the current to voltage converter. For the measurement of pyroelectric spectrum laser light is incident on the specimen, for the measurement of reference spectrum laser light is incident on the photo diode. Through a fast operational amplifier with a gain band width product of 1.7GHZ is used in the I-U converter, a significant amount of phase shift can be avoided in MHZ.1