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Studies on the pyroelectric materials for uncooled wideband infrared detectors
Dissertation/Thesis
Alabama A & M University. Department of Physics, Chemistry and Mathematics. (Degree grantor)Guggilla, Padmaja (thesis advisor)
2012
Alabama A & M University
The major problems experiences by some or most of the pyroelectric infrared (IR) sensors when the materials are taken into space is the crystalline structure modifications (crystal lattice destruction) when these material are exposed to ionic oxygen within the lower earth atmosphere. Some of those pyroelectric materials demonstrate superior dielectric properties. This remarkable and unique material properties makes the materials good potential for multilayer ceramic capacitators, sensors and actuators made of relaxers can have applications in the radiation environment such as space, nuclear reactors and nuclear waste containers. However, exposure of those materials (BM300, BM941, DTGS, PVDF, PMN-PT, and LT) to ion oxygen irradiations leads to modifications in their physical properties due to the defects formed in the lattice and to structural changes. Accordingly, such modification induced within the crystalline structure of the materials will vary according to the type of ceramic material. Piezoelectric and pyroelectric phenomena coexist on ferroelectric materials. Polycrystalline materials as well as single crystals showing ferroelectric behavior are used in electronics and optics. Though certain ferroelectric crystals show high pyroelectric performance, they are fragile in nature which causes technical difficulties in the processing. Ferroelectric materials are described as the polyelectric ceramics that acquire mechanical strength through a sintering process. The main challenge for thermal detectors and imaging devices has been to make a structure which has a measurable temperature rise for low radiation power and integration with integrated circuit (IC) technology. Previously, the fabrication of active pyroelectric devices have relied on bulk single crystal in which the sample must be cut, lapped, and polished down to the required possible thickness before hybridization to silicon IC. Ferroelectric ceramics possess a number of properties which make them very useful in a variety of applications. These include high dielectric constant, high pyroelectric constant, relatively low dielectric loss, high electrical resistivity, low moisture sensitivity, high electromechanical coupling, medium hardness, high optical transparency, and high electro-optical coefficient. Ferroelectric materials used in pyroelectric infrared detectors operate only below the Curie temperature Tc. This is because above Tc they get depoled. Ferroelectric oxide ceramics have a high Curie temperature such that there is no danger of depoling during normal usage over a wide range of ambient temperatures. Lead zirconate titanate (PZT) based polycrystalline ceramics are investigated before and after irradiation for their application in the space. Results show that the samples prepared are functional and are very promising as the temperature detectors in space. Keywords: Pyroelectric Infrared Sensor, polycrystalline ceramics, multi-layer ceramic capacitors, Irradiation, structural modification-- p. v-vi
PyroelectricityInfrared detectors
