The excellent properties of piezoelectric materials, like short reaction time and high precision, lead to several applications for instance in the automobile industry. One of the most important piezoelectric compositions is lead zirconate titanate, which is often used as a multilayer actuator in fuel injection systems in the automobile sector. The electro mechanical properties can be greatly influenced by the ferroelectric domain density orientation distribution function. In order to improve the properties and also the reliability of application, the domain orientation distribution needs being characterized. In this work, several piezo actuators with different pre – treatments (unpoled, poled and compressed) were analysed via polarised Raman spectroscopy. This technique was selected because the Raman signal is direction – dependent if the sample is rotated around its rotational axis. The focus of these measurements lay on the intensity dependence of the Raman spectrum from the rotation angle of the different samples. The amplitude and shape of the intensity vs. angle curve is in fact dependent on the local domain orientation distribution. The measurements were realized either on specimens in the remanent state in – situ by applying electric field or mechanical load during measurement. Further, the influence of the sample preparation route (first treatment then preparation or vice versa) on the surface sensitive Raman measurements was studied. In this respect, a particular chemo – mechanical preparation technique was used to clarify the preparation induced stresses and their influences on the Raman studies. The intensity dependences of the Raman spectra obtained out of these studies were used to simulate the domain orientation distribution function via a Reverse Monte Carlo (RMC) Simulation. To use this simulation it is necessary to know the elements of the Raman tensor of the material. Therefore a calibration measurement was used to determine these parameters. At the beginning of the simulation all crystals are taken as uniformly oriented. During the simulation the orientation of the crystals is altered until the difference of the intensity dependence of the simulated and measured signal is as small as possible. The result of this iterative procedure is the full domain orientation distribution function of the investigated samples. Furthermore, Vickers indentations on the same samples were used to qualitatively confirm the results of the polarized Raman measurements. From the different crack lengths originating from indentation corners it is possible to estimate qualitatively the overall orientation of the domains in the sample. These results were compared with the results of the Raman experiments. The indentations were applied in the remanent and in the in – situ compressed state with different compression stresses. In conclusion, the results of the experiments show that the intensity dependence of the samples in the remanent state is much smaller than in the in – situ treated state.
|Translated title of the contribution||Characterisation of the domain structure from piezoelectric actuators by polarized Raman Spectroscopy|
|Award date||18 Dec 2015|
|Publication status||Published - 2015|
Bibliographical noteembargoed until null
- pieoelectric actuators
- polarized Raman Spectroscopy
- indentation tests PZT