IR Detectors using Pb (Mg1/3Nb2/3) O3 and Pb (Sc1/2Ta1/2) O3 Ceramics under DC Bias

Recently, one of thermal-type IR detectors, a pyroelectric sensor has a great interest in applications to commercial uses because of their working temperatures without cooling, a constant detectivity with independent of wavelength and a cheaper price. The conventional pyroelectric materials are usually normal ferroelectrics with a first or a second phase transition. The working temperatures prefer to enough below the Curie temperature, Tc, for the stable responsivity to temperature. Electric field induced-type pyroelectric sensors have also been proposed. Relaxor ferroelectrics such as Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Sc1/2Ta1/2)O3 (PST) which have a glassy Curie temperature near room temperature are used as this type sensors. This paper describes the sensor properties of electric field induced-type pyroelectric sensors prepared by using PMN and PST ceramics compared with the conventional type sensors. Material evaluations of PMN and PST ceramics were made to dielectric and pyroelectric properties. PMN shows the excellent induced pryoelectric properties for the sensors over wide range of temperature. On the other hand, PST seems to be inadequate for an IR detector because of a very narrow temperature range to high response. Prepared sensors with PMN and PST ceramics show enhanced pyroelectric activities under DC bias field. Measured sensor voltage-responsivities agree with those of calculated values for the PMN case. The electric field induced-type infrared sensor with the thick or thin film materials seems to be fine as linear array IR detectors for thermal imaging by means of application of higher electric field.