Polarized Raman mapping study of the microheterogeneity in 0.67PbMg_1/3 Nb_2/3O₃‐0.33PbTiO₃ single crystal

Abstract

Polarized micro-Raman spectroscopy was carried out on the (001) face of a 0.67PbMg 1/3 Nb 2/3 O 3 -33%PbTiO 3 (PMN-33%PT) single crystal. The Raman images revealed the spatial variations of the intensity of the Raman bands, suggesting that the structure in the PMN-33%PT single crystal varied from one micro-area to another. When changing the polarization direction of the incident light with respect to the selected crystalline axes, the intensities of the Raman modes varied periodically. According to the Raman selection rules (RSRs), the angular dependences of the Raman modes indicated that the PMN-33%PT single crystal is in the monoclinic phase. Furthermore, the color patterns in the Raman images were associated with the coexistence of the M Aand M C -type monoclinic phases in the PMN-33%PT single crystal. Our results provide useful information for understanding the microheterogeneity of the relaxor PMN-xPT single crystals with compositions near the morphotropic phase boundary region.

Macroscopic lamellar heterophase pattern inPb(Mg1/3Nb2/3)O3

“…In fact, the angular dependence recorded in the dark and light areas here are also quite analogous to that of "G microregions" and "R microregions", respectively, discovered in PMN-0.33PT single crystals by authors of the Ref. 24 and then also reinvestigated in the temperature study of Ref. 30.…”

“…We used the latter ratio to map the stripes and observed that in contrast to results of Ref. 24, in our sample the so-obtained relative intensity map reveals clear, about 100-micron sized stripes, which clearly match the stripes observed optically (Fig. 3b).…”

“…Note that both these ratios were previously used in Ref. 24 for distinguish two types of coexisting structural "microregions" of irregular shape in PMN-0.33PT, assigned to the M A (i.e. rhombohedral-like phase) and M C (i.e.…”

Designing Monoclinic Heterophase Coexistence for the Enhanced Piezoelectric Performance in Ternary Lead-Based Relaxor Ferroelectrics

“…Heterophases in relaxor ferroelectrics lead to the misfit stress of lattice and consequently allow polarization heterogeneity for accommodating the stress. , The connections between polarizataion and structure were studied on the same region of Figure b by in situ micro-Raman imaging. Raman spectroscopy has a high sensitivity to the spatial phase variation by analyzing the soft-mode. ,, Under the same ambient pressure and temperature, the phonon frequency shift is mainly attributed to the intrinsic phase difference and the internal stress inhomogeneity. , Phonon frequency mappings around 55, 80, and 585 cm –1 in Figure f–h, respectively, clearly show a larger frequency on the left side, associating with the ribbon-shaped domain configuration, while the irregular domain area corresponds to the smaller frequency values. Similarly, Hlinka et al reported a macroscopic lamellar structure in PMN-0.32PT by polarized Raman spectroscopy, indicating an array of “morphotropic” interphase boundaries between R-like and T-like areas.…”

“…Phase instability and transverse phonon localization are the main causes for the emergence of metastable monoclinic (M) phase bridging rhombohedral (R) and tetragonal (T) symmetries. ,− Intermediate M-symmetry (M a , M b , and M c ) groups are believed to balance the accommodated strain and favor the multidirectional polarization states at MPB. ,− The as-grown PMN-based relaxor ferroelectric crystal has a rhombohedral-like (R-like) M a (space group Cm ) and tetragonal-like (T-like) M c (space group Pm ) phases coexisting at room temperature, presenting an adjacent laminar domain structure. ,− It should be noted that exploring Pb-based ferroelectric performances requires consideration of the synergistic contributions from the lattice symmetry, polar order, and internal energy. Therefore, it is necessary to explore the spatial relationships between the structure, internal energy, and polarization disorder in Pb-based relaxor ferroelectrics with MPB composition, and to further strengthen the understanding of the structure-related piezoelectric contributions.…”