Polarized Raman spectra of unpoled PZT–PNN–PZN, acquired in cross and parallel polarization configuration. The positions of normal and mixed Raman modes are labeled according to Table I. Letters refer to spectrally convoluted bands.
Intensity dependence of Raman modes, as retrieved in poled PZT–PNN–PZN material in different polarization configurations, (a) parallel and (b) cross, on the angle, , between crystal orientation and incident and scattered light vectors. The three modes are comprised in the broad convoluted band whose spectral deconvolution is given [in (c) and (d) for parallel and cross spectra, respectively] for the two extreme configurations at 0 and .
Schematic of a polycrystalline PZT–PNN–PZN bar loaded in a four-point flexure jig. The effect of applied stress on domain orientation is schematically drawn with reference to the selected crystal axes. The laboratory reference Cartesian system is also depicted.
Spectroscopic calibration results for [(a) and (b)] poled and [(c) and (d)] unpoled PZT–PNN–PZN materials in the cross and parallel configurations, respectively. The retrieved slope value for the parallel configuration is .
Domain orientation maps for [(a) and (b)] unpoled and [(c) and (d)] poled materials before and during loading in a four-point bending flexure configuration, respectively. The labeled lengths are in microns. The incident and scattered laser polarization vectors are directed along the direction, in parallel configuration. A schematic draft is given to show the location of the investigated area along the thickness of the bending bar.
Domain angular rotations due to applied stress during loading in a four-point bending flexure configuration. Data were fitted according to linear functions. Domain rotation is intended as the angular displacement occurred at any given location in the loaded configuration with respect to the unloaded state.
Angular dependence of for a poled PZT–PNN–PZN material (a). Details of the fitting procedure are given in (b) and (c) for spectra acquired at and , respectively.
Phonon modes for undoped PZT–PNN–PZN and qualitative description of their angular dependence (from the present assessments in agreement with Ref. 18).(엯) refers to a strong dependence, and (▵) to a slight dependence, and (×) to independent modes. Modes are grouped according to their spectrally convoluted bands (cf. Fig. 1), whose average maximum values are also provided.
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