Preparation Of PIMNT Relaxor Ferroelectric Thin Films And Study Of Thickness Size Effect

Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-Pb Ti O₃(PIMNT)relaxor ferroelectric single crystal has a wide application prospect in many high-tech fields such as piezoelectric transducer and pyroelectric infrared detector because of its excellent ferroelectric,piezoelectric,pyroelectric and nonlinear optical effects.If we can further develop micron thick high-quality sensing films,it is of great significance to improve the performance of array pyroelectric infrared detector and piezoelectric micro/nano sensor.This paper focuses on the preparation,structure and electrical properties of quasi homomorphic phase boundary tripartite phase 0.36Pb(In_1/2Nb_1/2)O₃-0.36Pb(Mg_1/3Nb_2/3)O₃-0.28Pb Ti O₃[PIMNT(36/36/28)]relaxor ferroelectric thin films.The main research contents and results are as follows:(1)Firstly,using nickel acetate and lanthanum nitrate as raw materials,the conductive buffer layer La Ni O₃(LNO)with perovskite structure and small roughness was prepared on Pt/Ti/Si O₂/Si substrate by Sol-gel process,which effectively solved the problem of lattice mismatch between films and substrates,eliminated pyrochlore phase and greatly improved the crystal quality of PIMNT ferroelectric thin films.By controlling the orientation of the buffer layer,the PIMNT(36/36/28)films were grown along with the(110)orientation.Then,a stable PIMNT(36/36/28)precursor was prepared from lead acetate,magnesium acetate,indium acetate,niobium ethoxide and tetrabutyl titanate.The effects of the buffer layer and annealing conditions on the crystal quality,surface morphology,stress state,electrical properties and domain structure of the films were systematically studied.The results show that the unpoled PIMNT(36/36/28)ferroelectric films exhibit compact morphology and excellent dielectric,ferroelectric,piezoelectric and pyroelectric properties.When the annealing temperature is 650?and the single-layer annealing time is 5 min,the optimized dielectric constant and loss are 2190 and 0.029 at 1 k Hz,and the remnant polarization P_r and coercive field E_C are 19.15?C/cm² and 4.96 k V/mm,respectively.The leakage current density is as low as 1.76×10^-15 A/cm²at low electric field.Under the action of an in-situ DC electric field,the domain evolution process was investigated by piezoelectric force microscopy(PFM),the domain inversion of 180°and the local piezoelectric response of the"butterfly"shape were observed.(2)PIMNT ferroelectric thin films with different thicknesses were prepared on Pt/Ti/Si O₂/Si substrates.The thickness size effect of the films was studied,it was found that with the increase of thickness,the dielectric constant showed a gradually increasing trend,the residual polarization value first increases and then decreases,and the coercivity field gradually increases.Annealed at 650°C for 1 h,the dielectric constant and loss of the 1?m PIMNT films after poled are 1009 and 0.022 at 100 Hz,respectively,and the pyroelectric coefficient at room temperature is as high as 6.85×10^-4 C/m²·K,the current response figure of merit F_i,the voltage response figure of merit F_v and the detection rate figure of merit F_d reach 2.74×10^-10 m/V,0.031 m²/C,and1.96×10^-5 Pa^-1/2,respectively.The macroscopic quasi-static piezoelectric coefficient reaches 153 p C/N.The excellent comprehensive performance makes PIMNT(36/36/28)films in this paper very suitable for the application of integrated pyroelectric and piezoelectric devices.