Research And Application Of PIMNT Single Crystal Pyroelectric Infrared Detector

The range of where sensors have been used is growing with the development of industrial and living intelligence,and sensor accuracy is also being demanded higher by people.Infrared detectors are widely used in military,medical,industrial detection,security alarm,gas detection,and other fields.Among them,pyroelectric infrared detectors have the advantages of don’t need refrigeration,wide spectral response,fast response,long life,good anti-interference performance,and low cost compared with other infrared detectors,and therefore it has broad application prospects in military and civilian fields.The pyroelectric-sensitive element is the core of the pyroelectric infrared detector.Mn-doped tripartite ferroelectric crystal Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-Pb Ti O₃（Mn-PIMNT）has excellent pyroelectric properties,dielectric properties,and high Curie temperature.In this thesis,pyroelectric-sensitive elements,detector structures,and gas detection are studied according to the performance requirements and actual use requirements of high-performance pyroelectric infrared detectors.The content and results of the study are as follows:（1）It was revealed that the size effect and surface effect of Mn-PIMNT monocrystalline thinning,as well as the influence on monocrystalline domain structure,dielectric,ferroelectric,and pyroelectric properties.As the thickness of the pyroelectric-sensitive element decreases,the dielectric constant and dielectric loss of the unpolished sample increase,and the pyroelectric coefficient decreases(@14μm,p=4.9×10^-4 Cm^-2K^-1),while the dielectric loss and dielectric constant of the pyroelectric-sensitive element decrease after polishing,the pyroelectric coefficient is significantly improved(@15μm,p=10.4×10^-4 Cm^-2K^-1).Ultra-thin sensitive elements with excellent comprehensive performance（as low as 15μm）were prepared by improving the chemical mechanical polishing method（CMP）and A single-channel pyroelectric infrared detector was further prepared,and its normalized detectivity could reach 1.03×10⁹ cm Hz^1/2W^-1.（2）The theoretical model of the Mn-PIMNT pyroelectric infrared detector was improved,and the effects of different thermal structures on the thermal equilibrium time and temperature rise of the detector are simulated by Comsol simulation software.The effect of different feedback resistors and capacitors on detector performance was simulated by Matlab,and detectors with different feedback circuits were prepared.The difference between the actual performance of the detector and the simulation results were analyzed,and the high magnification feedback circuit benefit to reduce environmental interference to the detector.The noise formula of the series compensation structure detector was deduced,and the series-compensated detector with a sensitivity element of 25μm was prepared.The voltage responsivity,noise,normalized detectivity of the series compensation detector reached 2.25×10⁵ V/W、65.9μV/Hz^1/2、6.92×10⁸ cm Hz^1/2W^-1 respectively.Although the normalized detectivity was reduced after series compensation(uncompensated9.11×10⁸ cm Hz^1/2W^-1),the vibration resistance,temperature stability,and high-frequency response stability of the detector are significantly improved.（3）A dual-channel pyroelectric infrared gas detection model was established,a CO₂ gas detection system was prepared and a gas concentration algorithm was established.The detection accuracy,resolution,repeatability,and linearity of the CO₂gas detection system were verified.The accuracy of the CO₂ gas detection system can reach 9 ppm±1.1%reading.