| Flexible pyroelectric sensing films,based on the pyroelectric effect,are used to detect infrared radiation and are the core components for flexible infrared detection and imaging.Therefore,flexible pyroelectric films have great potential for applications in fields such as flexible multifunctional sensors and wearable devices.However,the performance of flexible pyroelectric films based on polyvinylidene fluoride(PVDF)and its copolymer polyvinylidene fluoride-trifluoroethylene(P(VDF-TrFE))is currently low,which limits their practical use.To obtain high-performance flexible pyroelectric films,this study first synthesized lithium tantalate nanorods(LTnrs)using a molten salt method,and then prepared flexible pyroelectric composite films doped with LTnrs as the dopant phase and using P(VDF-TrFE)as the main pyroelectric material.The morphology,composition,pyroelectric,piezoelectric,and dielectric properties of the resulting films were systematically characterized.The main research content is as follows:(1)The synthesis of lithium tantalate nanorods was carried out using tantalum oxide and lithium carbonate as LTnrs precursors,potassium chloride as an additive,and nitrogen as a protective gas.The experimental results showed that the following process parameters could obtain the best experimental results in terms of the purity of the synthesized product,the aspect ratio of the nanorods,and the content of the nanorods:the molar ratio of tantalum oxide,lithium carbonate,and potassium chloride was 1:1:50;the temperature was ramped up to 850℃at a rate of 40℃/min,held at 850℃for 30minutes,and finally cooled to room temperature at a rate of 40℃/min;the reaction product was obtained after three washings.Under these experimental conditions,the diameter of the synthesized LTnrs ranged from 100 to 800 nm,and the length ranged from 5 to 40μm..(2)The synthesized nanorods were modified with polydopamine(PDA)(hereinafter referred to as PDA@LTnrs),and then PDA@LTnrs,synthesized lithium tantalate nanorods and commercial lithium tantalate nanospheres were used as dopants,respectively.Using P(VDF-TrFE)as the main material,pyroelectric composite thin films with different doping ratios were prepared by scraping film process.LTnrs scanning electronic microscope observation results show that the surface of the composite film mixed with PDA@LTnrs is smooth and no defects.Fourier’s infrared transmission spectrum(FTIR)analysis shows that as the PDA@LTnrs content increases,theβphase and relative permittivity of the composite film first increased and then decreased,Among them,when the doped concentration is 9 wt%,the content ofβphase is the highest,reaching 52.2%,and when the doping concentration is 5 wt%,the relative permittivity reaches the maximum of 31.(3)The thermal pyroelectric coefficients of the composite films were successfully measured using a low-frequency sine wave temperature control method.The results showed that the pyroelectric coefficients of the three samples at different doping concentrations were obtained.It was found that the commercial lithium tantalate had a maximum value of 40μC/m~2K at a doping concentration of 5 wt%,the synthesized lithium tantalate nanorods had a maximum value of 45μC/m~2K at a doping concentration of 7 wt%,and the dopamine-treated synthesized nanorods had a maximum value of 132μC/m~2K at a doping concentration of 9 wt%,which were all superior to the undoped pyroelectric films.The piezoelectric tests showed that the piezoelectric current signals of the various composite films were 87.6 n A(7 wt%nanorod composite film)and 64.4 n A(9 wt%PDA@LTnrs composite film),respectively,at the doping concentration that yielded the maximum pyroelectric coefficient. |
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