Origin of the large piezoelectric activity in(1−x)Ba(Zr0.2Ti

Abstract

The diffusionless pseudobinary phase diagram, monodomain properties, and free energy of (1 − x)Ba(Zr 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 are computed for comparison with experimental results. Specifically, the variation of the spontaneous polarization, anisotropy energy, and free energy with respect to temperature, composition, and polarization direction are discussed relative to the results of resonant piezoelectric measurements performed over a wide compositional range as a function of temperature. The phase angle, relative permittivity, piezoelectric and coupling coefficients, and elastic compliances were used to investigate relations between the computed and measured pseudobinary phase diagrams and the measured piezoelectric and elastic properties. It was found that d 33 values along the orthorhombic to tetragonal phase boundary are ∼30% higher than those both along the rhombohedral to orthorhombic phase boundary and in the region where phases converge. It is shown that the reduction in anisotropy energy in these regions of the phase diagram is by itself insufficient to explain the measured properties. The highest small signal piezoelectric activity is found along the orthorhombic to tetragonal phase boundary due to a combination of reduced anisotropy energy, high remanent/spontaneous polarization, and increased elastic softening. The combined computed and experimental results are used to demonstrate that the interdependent behavior of these properties should be considered in the design of engineered piezoelectric ceramics.

Recent Progress on BaTiO3-Based Piezoelectric Ceramics for Actuator Applications

“…Liu and Ren proposed that large the piezoelectric response for BZT-BCT is associated with the starting point of MPB, i.e., the C-T-R triple point, which shows a tricritical behavior with the crossover between first order and second order transition (as shown in Figure 12) [14]. On the other hand, it has also been proposed that there is no need for the coincidence between the tricritical point and the triple point, and Acosta et al pointed out that the maximum coefficient d 33 value (best piezoelectric property) does not occur at the triple point [74][75][76]. This indicates the irrelevance between the tricritical point and the high piezoelectric response.…”

Influence of local strain heterogeneity on high piezoelectricity in 0.5Ba(Zr0.2Ti0.8)Zhang1, Ren2, Carpenter3 2017Phys. Rev. B220180View full textAdd to dashboardCite

“…[11,13,14,21] The overall pattern of softening and stiffening observed here both at 0. with BTO is revealing, however, in that, while there are some close similarities in the mechanical properties, there are also some important differences.…”

“…Precursor softening evident in Figure 4 for both BTO and BZT-50BCT is the same as has been reported previously for RUS data from BTO [30][31][32] and is attributed largely to the effect of dynamical polar nanoregions (PNRs). These acquire a static or quasi-static component that is most likely responsible for the anelastic loss seen as increasing tanδ and Q -1 from ~10-20 K above T c , and would account also for the small residual values of the piezoelectric coefficient in a 10 K interval above T c reported by Acosta et al [11] and in a 30 K interval above T c by Damjanovic et al [29] This effect can also be observed in the dielectric results of BZT-50BCT in Fig.3c.…”

“…In terms of the properties which particularly lead to high piezoelectric coefficients, Acosta et al showed that the highest value of d 33 occurs at T T-O in BZT-50BCT and that this coincides with the maximum value of the elastic compliance, s 33 . [11] They showed also that the elastic compliance is more important than elastic anisotropy in determining the piezoelectric response. Here we have extended the frequency range of elastic measurements to confirm the results of Cordero et al [16] for the minimum shear modulus (maximum compliance) as well as the wider pattern of stiffening/softening with temperature.…”

“…[11][12][13][14][15][16][17][18] At least part of the high piezoelectric effect in BZT-50BCT might also be attributable to the mobility of twin walls in nanoscale adaptive microstructures associated with the phase boundaries. [19][20][21] It must be expected that extrinsic and intrinsic effects associated with the phase transitions, the adaptive microstructures and twin wall motion could be distinguished on the basis of measurements of both dielectric and elastic responses at different frequencies.…”