Structure And Electric Properties Of The PZT/CCTO Multilayer Thin Films

In this paper, we prepared the PZT and CCTO collosol employing sol-gel process. The affection of the different technological parameters to the structure and properties of multilayer thin films were studied by changing the technological parameters of the preparation of thin films such as concentration of the CCTO precursor, annealing method, annealing temperature, structure of the multilayer thin films and dopping of the lanthanum. The surface and section of the multilayer thin films, phase structure, ferroelectric and dielectric properties were studied by SEM, XRD, Ferroelectric analyzer and Precision impedance analyzer respectively.The research results indicate that the PZT thin films we prepared are pure perovskite phase, and all of the PZT thin films we prepared show the strong (100) preferred orientation. The pure CCTO phase which shows the strong (100) preferred orientation was acquired in the manner of traditional annealing when the CCTO precursor concentration was 0.05M. The PZT thin films reveal excellent ferroelectric properties owing to its bigger remanent polarization and lower coercive field. The CCTO thin films show the hysteresis loops of non-ferroelectric properties whose leakage current are larger. Due to the bigger changes of the dielectric constant of CCTO thin films with the prepared technology, we can prepare the CCTO thin films whose dielectric constant is less than 100.The research results of the PZT/CCTO multilayer thin films show that the different precursor concentrations of CCTO have a significant effect on the thin films of the PZT/CCTO sandwich structure (5 layers). Composed with the CCTO thin films which have the precursor concentration of 0.02M, the multilayer thin films show the strong (100) preferred orientation of PZT's owing to the thinner films of CCTO which have the thickness of 26 nanometers. The preferred orientation of the multilayer thin films disappears with the increase of the precursor concentrations, namely the thickness of CCTO thin films in the sandwich structure. Using the composite patterns of PZT/xCCTO/PZT and controlling the thickness of CCTO interlayer, the phase of the multilayer thin films indicates that the thin films only have the diffraction peaks of PZT when the thickness of CCTO interlayer is less than 26 nanometers, and the diffraction peaks of both PZT and CCTO appear simultaneously in the multilayer thin films when the thickness of CCTO interlayer is more than 39 nanometers. The description above indicate that only the thick CCTO layer can the CCTO prompt to crystallize in the PZT/CCTO multilayer thin films.The measurement results of electric properties of multilayer thin films indicate that we can acquire the abnormal ferroelectric properties by controlling the thickness of CCTO thin films and the states of crystallization rationally. While keeping the big value of remanent polarization, the big coercive field is up to 1400kV/cm which is 3 times than the biggest value reported in the document at present.The multilayer thin films having the big value of coercive field have the big pyroelectric coefficient. We can obtain the small values of dielectric constant and dielectric loss by controlling the technology parameters in order to require the great detection value which can settle the materials base for the research of the uncooled infrared detector.