Pyroelectric Properties And Size Effect Of Rhombohedral Relaxor Ferroelectric Single Crystals

The pyroelectric infrared detector with pyroelectric material as sensitive element is widely used in military and civil fields because of its wide spectrum response range,no need of refrigeration,fast response,low cost,simple structure,small size,light weight,good concealment and strong anti-interference.At present,the demand for high-performance pyroelectric infrared detector is increasingly prominent.The development of pyroelectric materials with high performance and stability is of great significance to improve the performance of devices.At the same time,reducing thermal capacity of pyroelectric materials by reducing the thickness,the response rate and detection rate of detectors can be improved.In order to further promote the development of pyroelectric detector performance,the pyroelectric properties,preferred value factors,temperature stability and thermal stability of rhombohedral(111)-oriented Mn?PIMNT(36/36/28)single crystal,and the thickness size effect of the pyroelectric properties of rhombohedral(111)-oriented PMNT(72/28)single crystal was studied.The main research contents and results are as follows:The phase structures,pyroelectric properties,as well as thermal stability of Mn?PIMNT(36/36/28)single crystal were investigated.The temperature dependence of Raman spectra and dielectric properties reveals that the crystal exhibits a rhombohedral structure at room temperature,and gives rise to ferroelectric rhombohedral to tetragonal and ferroelectric tetragonal to paraelectric cubic phase transitions at 130 ? and 175 ?,respectively,as well as a reduction of long-range order at 140 ?.And the single crystal shows low relative permittivity of tan ? ~ 0.0003 and loss tangent of ?r = 505,high remnant polarization of Pr = 38 ?C/cm2 and coercive field of EC = 12 k V/cm at room temperature at 100 Hz.They decrease with temperature increasing and present anomalies near phase transition temperatures,which coincides with the results of Raman spectra and dielectric properties.Moreover,the single crystal has high pyroelectric coefficient of p = 8.7 × 10-4 C m-2 K-1 and figures of merit for a current responsivity of Fi = 3.5 × 10-10 m V-1,a voltage responsivity of Fv = 0.08 m2 C-1,and a detectivity of Fd = 30.1 × 10-5 Pa-1/2 at 100 Hz at 25 ?.They are weakly dependent on temperature below 120 ?.In addition,the room-temperature pyroelectric coefficients of the single crystal maintain over 83% of the original value at thermal annealing temperatures below 120 ?.The outstanding pyroelectric properties together with high thermal stability indicate the [111]-oriented rhombohedral Mn?PIMNT(36/36/28)single crystal a new potential candidate for infrared detection applications.Based on the improvement of the response rate,detection rate and temperature stability of the device,the structure and performance of the pyroelectric material,the core component of the pyroelectric detector,are studied in this paper.The results show that the rhombohedral [111] oriented Mn pimnt(36/36/28)and PMNT(72/28)relaxor ferroelectric single crystals have potential advantages in the application of the detector.