Enhanced ferroelectric and piezoelectric properties of BCT-BZT at the morphotropic phase boundary driven by the coexistence of phases with different symmetries

Abstract

The discovery of lead-free piezoelectric materials is crucial for future information and energy storage applications. Enhanced piezoelectric and other physical properties are commonly observed near the morphotropic phase boundary (MPB) composition of ferroelectric solid solutions. The (1-x)Ba(Zr 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 (BZT-xBCT) system exhibits a large electromechanical response around its MPB region at x=0.5. We report experimental and theoretical results of BZT-xBCT over a wide composition range (0.3≤x≤1.0). X-ray diffraction and Raman spectroscopy studies indicate a composition-induced structural phase transition from a rhombohedral (R3m) phase at x≤0.4 to a tetragonal (P4mm) phase at x≥0.6 through a multiphase coexistence region at 0.45≤x≤0.55 involving orthorhombic + tetragonal (Amm2+P4mm) phases. First-principles calculations elucidate the phase competition in the coexistence region. The critical composition (x= 0.5) displays enhanced dielectric, ferroelectric and piezoelectric properties, where notably d 33 ~ 320 pC/N. This work provides clear evidence of Amm2+P4mm crystallographic phases in the MPB region, which is responsible for the improved functional properties.

Strain Engineering of Two-Dimensional Piezophotocatalytic Materials for Improved Hydrogen Evolution Reaction

“…For instance, at the maximum tensile strain considered in this study, we estimate Z W = −0.72 e , Z Se = +0.36 e , and ε r = 0.035 for WSe 2 and Z W = −0.44 e , Z S = +0.22 e , and ε r = 0.016 for WS 2 . Thus, despite that these latter results appear to suggest that WSe 2 is a better piezoelectric material than WS 2 (i.e., larger piezoelectric coefficients typically are accompanied by larger Born effective charges and dielectric constants), , the total ε yy values obtained for WS 2 are larger than those obtained for WSe 2 due to the constructive addition of the electronic and ionic parts in the former system and opposing in the latter.…”

First-principles high-throughput screening of bulk piezo-photocatalytic materials for sunlight-driven hydrogen production

“…1c). It is noted that large piezoelectric stress constants typically are accompanied by also large dielectric constants, 24,25 thus it is naturally difficult to find materials with large band-alignment piezo tunability ( i.e. , large α η values).…”

“…1c). It is noted that large piezoelectric stress constants typically are accompanied by also large dielectric constants, 24,25 thus it is naturally difficult to nd materials with large band-alignment piezo tunability (i.e., large a h values). This small set of conditions are not only physically insightful but also computationally convenient: the relevant quantities E g , ˛and e 33 can be efficiently estimated via bulk rst-principles DFT calculations.…”

High-throughput screening of piezo-photocatalytic materials for hydrogen production

“…Consequently, piezoelectric materials possessing energy band gaps in the range of 1.23 E g 3.0 eV (to absorb the sunlight visible radiation), small dielectric constants and large piezoelectric stress coefficients (the last two conditions as for maximizing ∆V i ), a priori should be regarded as promising piezo-photocatalysts. It is noted that large piezoelectric stress constants typically are accompanied by also large dielectric constants [24,25], thus the natural difficulty in finding materials with large band-alignment piezo tunability (i.e., large α η values). This small set of conditions are not only physically insightful but also computationally convenient: the relevant quantities E g , and e 33 can be efficiently estimated via bulk firstprinciples DFT calculations [26][27][28].…”