Design,Fabrication And Application Investigations Of The PIMNT Single Crystals Based Pyroelectric Infrared Detectors

As a high-tech detection technology,infrared detection technology has drawn much attention with the progress of human civilization and the rapid development of science and technology.The infrared detectors have been widely used in the fields of military,industrial,medical,security,agriculture,and so on.Pyroelectric infrared detectors,one of the key points in the research and application of uncooled infrared detection technology,exhibit many advantages compared to other infrared detectors,such as fast response,no refrigeration,wide spectral response range,low cost and so on.The pyroelectric materials are the core of pyroelectric infrared detectors.The large size and high quality（1-x）Pb(Mg_1/3Nb_2/3)O₃-x Pb Ti O₃（PMNT or PMN-PT）relaxor ferroelectric single crystals synthetized by the improved Bridgman method are a new generation of pyroelectric materials,but their relatively lower Curie temperature T_Cand phase transition temperature T_R-T,from rhombohedral phase to tetragonal phase,limit their temperature application range to a certain extent.The new ternary relaxor ferroelectric single crystals Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-Pb Ti O₃（PIMNT or PIN-PMN-PT）also exhibit excellent pyroelectric properties with relatively higher phase transition temperature,indicating that the corresponding infrared detectors can be used at higher temperature and present higher temperature stability.In order to prepare the PIMNT pyroelectric infrared detectors with high detection and stable application,the investigations were carried out from the following four aspects.In part one,the theoretical model of current mode the PIMNT infrared detectors was improved.The influence of the performance parameters of the PIMNT sensitive elements and circuit parameters on the responsivity R_V,noise u_n and specific detectivity D*of the detectors were simulated and analyzed,providing the theoretical guidance for the performance optimization of the PIMNT single crystals and the design of the pyroelectric detector structures.In part two,ultra-thin PIMNT sensitive elements with high pyroelectric properties and low dielectric loss were developed.By increasing the single domain degree,the figure of merit（FOM）for detectivity F_d is increased by 2.6 times for the rhombohedral PIMNT single crystals,and 4.2 times for the tetragonal PIMNT single crystals.By the two-step annealing processes before and after thinning and polishing the PIMNT crystals,the oxygen vacancies(1(1^··is reduced and the surface stress is released,increasing F_d of the PIMNT sensitive elements by 1.7 times and 0.3 times for the first and second annealing process,respectively.In part three,the PIMNT pyroelectric infrared detectors with excellent performance were designed and fabricated.The specific detectivity D*of the designed PIMNT detectors are 1.56×10⁹ cm·Hz^1/2·W^-1 for the separated compensated and1.19×10⁹ cm·Hz^1/2·W^-1 for the integrated compensated,respectively.The microphonic noise of the PIMNT compensated pyroelectric infrared detectors at 10 Hz is reduced from 4-5 m V to 1-2 m V,greatly improves the stability of the detectors.In part four,non-dispersive infrared（NDIR）CH₄ gas sensors based on the dual channel compensated PIMNT pyroelectric infrared detectors were developed.The error of the newly calibrated CH₄ gas sensors is within±0.5%in the range of 0～10420 ppm,confirming the application advantages of the PIMNT pyroelectric single crystals based infrared detectors with high performance in NDIR gas detection.