| High temperature piezoelectric sensors and actuators are required in modern industry such as automobile and aerospace. Morphotropic phase boundary (MPB) PZT has been widely used due to its high Curie temperature of386℃. Generally, the working temperature of piezoelectric materials is below half their Curie temperatures so that PZT can not be applied in temperature higher than200℃. In terms of the relationship between the tolerance factor (t) and Curie temperature, a new type solid solution of lead titanate (PT) and bismuth-containing perovskite materials has attracted increasing attention. The chemical formula of this material can be written as Bi(Me)O3-PbTiO3where Me is Sc, In, Y, Yb, etc. As BiScO3has a smaller tolerance factor oft=0.907, BiScO3-PbTiO3(BS-PT) has been intensively studied in both bulk and thin film forms. However, the high price of Sc hinders the further application of this kind of material. As an alternative, xBiInO3-(1-x)PbTiO3(xBI-PT) has triggered much attention due the cheaper price of In as well as the smaller t factor t=0.884compared to that of Sc.However, only15BI-PT thin films deposited by PLD have been reported to the best of our knowledge currently. Other ratios of BI and PT have not been reported in neither bulk and thin film forms. Meanwhile, the ferro-, piezo-and dielectric behavior s of xBI-PT with x greater than0.20are not available till now maily due to the poor stability of the thermodynamic structure when x≥0.15. On the other hand, viewpoints over the position of MPB of xBI-PT have not yet reached a consensus:Density-functional theory calculations suggested that the MPB of BI-PT would be at0.33BI-0.67PT. In contrast, other experimental work suggests that the MPB would appear somewhere between5%-15%BI. So the study of BI-PT with broader BI/PT ratio should be conducive to our understanding of this kind of material, especially their ferroelectric, piezoelectric and dielectric properties. The main results of this dissertation are as follows:High-temperature piezoelectric thin films of0.20BiInO3-0.80PbTiO3(20BI-PT) were prepared via pulsed laser deposition and investigated by comparison with0.15BiInO3-0.85PbTiO3(15BI-PT). XRD patterns show that (100) peak of20BI-PT has been split, indicating a higher tetragnality than in15BI-PT. FESEM images reveal some triangular grains corresponding to (111)-oriented grains in20BI-PT. The remanent polarization (Pr) and coercive field (Ec) of20BI-PT are-28μC/cm2and-120kV/cm, respectively. It is shown that the transverse piezoelectric coefficient e31,f keeps almost the same in20BI-PT and15BI-PT. The temperature dependence of dielectric permittivity in20BI-PT reveals a higher Curie temperature (590℃) than that in15BI-PT and no apparent frequency dependence is detected. Rayleigh analyses are performed to identify the extrinsic contributions to dielectric nonlinearity for different x. It is seen that x=0.15exhibits greater extrinsic contributions to dielectric nonlinearity than the other compositions.High temperature piezoelectric thin films xBiIn03-(1-x)PbTi03(xBI-PT, x=0.15,0.20,0.25,0.35) were prepared via pulsed laser deposition. X-ray diffraction patterns show that all xBI-PT exhibit pure phase perovskite structure with (001) preferred orientation. With increasing x, the relative (111) orientation increases. Compared with x=0.15, the remanent polariza-tion (Pr) of x=0.20increases a little while the coercive field (Ec) is also increased. The Pr of x=0.25decreases a little compared to x=0.15. Under～700kV/cm applied field, the Pr and Ec of x0.15are～24μC/cm2and～93kV/cm, re-spectively. For x=0.20, the Pr is-28μC/cm2and Ec is-125kV/cm. The Curie temperature increases with increasing x and the value for x=0.25is as high as621℃. It is seen that x=0.15exhibits greater extrinsic contributions to dielectric nonlinearity than do the other compositions based on Rayleigh law. |
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