Articles you may be interested inElectric-field-temperature phase diagram of the ferroelectric relaxor system (1−x)Bi1/2Na1/2TiO3−xBaTiO3 doped with manganese J. Appl. Phys. 115, 194104 (2014); 10.1063/1.4876746Long ranged structural modulation in the pre-morphotropic phase boundary cubic-like state of the lead-free piezoelectric Na1/2Bi1/2TiO3-BaTiO3 J. Appl. Phys. 114, 234102 (2013) On the phase identity and its thermal evolution of lead free (Bi 1/2 Na 1/2 )TiO 3 -6 mol% BaTiO 3 Temperature-dependent dielectric permittivity of 0.94(Bi 1/2 Na 1/2 )TiO 3 -0.06BaTiO 3 (BNT-6BT) lead-free piezoceramics was studied to disentangle the existing unclear issues over the crystallographic aspects and phase stability of the system. Application of existing phenomenological relaxor models enabled the relaxor contribution to the entire dielectric permittivity spectra to be deconvoluted. The deconvoluted data in comparison with the temperature-dependent dielectric permittivity of a classical perovskite relaxor, La-modified lead zirconate titanate, clearly suggest that BNT-6BT belongs to the same relaxor category, which was also confirmed by a comparative study on the temperature-dependent polarization hysteresis loops of both materials. Based on these results, we propose that the low-temperature dielectric anomaly does not involve any phase transition such as ferroelectric-toantiferroelectric. Supported by transmission electron microscopy and X-ray diffraction experiments at ambient temperature, we propose that the commonly observed two dielectric anomalies are attributed to thermal evolution of ferroelectric polar nanoregions of R3c and P4bm symmetry, which coexist nearly throughout the entire temperature range and reversibly transform into each other with temperature.

In recent years, the stability field of a monoclinic phase at the morphotropic phase boundary in lead zirconate titanate, Pb͓Zr 1−x Ti x ͔O 3 , has been under discussion. In the present study, we investigated samples in the compositional range between 0.40ഛ x ഛ 0.475 and x = 0.55 using high-resolution synchrotron x-ray diffraction in combination with transmission electron microscopy and electron paramagnetic resonance to correlate average structure and microstructural information. It is shown that the microstructure plays a crucial role in the analysis of diffraction data. The appearance of intensity in diffraction patterns formerly linked to a monoclinic phase ͓B. Noheda et al., Phys. Rev. B 61, 8687 ͑2000͔͒ can directly be correlated to a miniaturization of the average domain structure of the material visible in the presence of nanodomains. The internal symmetry of the nanodomains is not necessarily monoclinic due to coherence effects in diffraction and is discussed with respect to martensitic theory.

Recently developed lead‐free incipient piezoceramics are promising candidates for off‐resonance actuator applications with their exceptionally large electromechanical strains. Their commercialization currently faces two major challenges: high electric field required for activating the large strains and large strain hysteresis. It is demonstrated that design of a relaxor/ferroelectric composite provides a highly effective way to resolve both challenges. Experimental results in conjunction with numerical simulations provide key parameters for the development of viable incipient piezoceramics.

The composition dependent variation of domain configuration and size in Pb(Zr1−xTix)O3 (PZT) has been investigated in a detailed transmission electron microscopy study in the range of 0.40⩽x⩽0.55. Single phase composition, Pb(Zr0.45Ti0.55)O3 and Pb(Zr0.60Ti0.40)O3, the former belonging to the tetragonal, the latter to the rhombohedral phase, feature small microdomain widths coupled with a pronounced bimodal domain distribution. Samples with compositions around the morphotropic phase boundary exhibit a decrease of bimodal distribution and an increase in microdomain width associated with nanodomain formation. The investigation of micro- and nanodomains, as well as the bimodal distribution of microdomains in undoped PZT ceramics, with respect to composition, is reported. We define nanodomains as “domains arranged within microdomains possessing a width of a few nanometers.” The strict alternation of the two orientation variants of microdomains is denoted as “bimodal domain distribution,” and is characterized by narrow and broad microdomains, which join each other in turn.

The design of core-shell materials affords additional degrees of freedom to tailor functional properties as compared to solid solution counterparts. Although to date most of the work in core-shell materials has focused on dielectrics, piezoelectric coreshell ceramics may gain similar interest. Generalities of core-shell functional ceramics features are addressed in this work. A model system, Bi 1/2 Na 1/2 TiO 3 -SrTiO 3 , is introduced to discuss structure-property relationships. We demonstrate that this system features a core-shell microstructure for the composition corresponding to 25 at.% Sr. The material is studied by means of macroscopic functional properties and in situ structural characterization techniques at different length scales, such as X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The evolution of the core-shell with field and temperature determines its functional properties. The high strain of the system, 0.3% at 4 kV/mm, is due to an electric-field-induced phase transition of the core and shell. Upon field removal the core remains in a poled state, whereas the shell is characterized by a reversible transformation. The reversibility of the phase transition of shells and associated switching are key features in the observed giant strain. Dielectric anomalies are found to be related to changes in oxygen octahedral tilting angles within the core and shell.