Large piezoelectricity and dielectric permittivity in BaTiO ₃ -xBaSnO ₃ system: The role of phase coexisting

Abstract

We report ultrahigh dielectric and piezoelectric properties in BaTiO3-xBaSnO3 ceramics at its quasi-quadruple point, a point where four phases (Cubic-Tetragonal-Orthorhombic-Rhombohedral) nearly coexist together in the temperature-composition phase diagram. At this point, dielectric permittivity reaches ∼ 75000, a 6-7-fold increase compared with that of pure BaTiO3 at its Curie point; the piezoelectric coefficient d33 reaches 697 pC/N, 5 times higher than that of pure BaTiO3. Also, a quasi-quadruple point system exhibits double morphotropic phase boundaries, which can be used to reduce the temperature and composition sensitivity of its high piezoelectric properties. A Landau-Devonshire model shows that four-phase coexisting leading to minimizing energy barriers for both polarization rotation and extension might be the origin of giant dielectric and piezoelectric properties around this point.

Recent Progress on BaTiO3-Based Piezoelectric Ceramics for Actuator Applications

“…The system shows anomalies of both small field (dielectric and piezoelectric) and large field (P-E hysteresis) properties at the MPB, and especially the d33 coefficient can reach 550 pC/N at room temperature, which further verifies the generality for such a design idea. Further large piezoelectric properties with d33 of 697 pC/N have been found in BaTiO3-xBaSnO3 Pb-free ferroelectric system ( Figure 16) [89]. By re-examining the Sn-doped BaTiO3, we found it also exhibits a T-O phase boundary.…”

“…Therefore, it is highly possible that the multi-phase coexisting point (i.e., quadruple point or triple point) is of great significance for the piezoelectric response of ferroelectric system, which might provide a guideline for developing Pbfree piezoelectric materials with large electrometrical responses. Further large piezoelectric properties with d 33 of 697 pC/N have been found in BaTiO 3 -xBaSnO 3 Pb-free ferroelectric system ( Figure 16) [89]. By re-examining the Sn-doped BaTiO 3 , we found it also exhibits a T-O phase boundary.…”

Some strategies for improving caloric responses with ferroelectrics

“…Similarly, a giant piezoelectricity was reported near a kind of quasi-critical point 43,44 composition where phases with different symmetries coexist allowing the polarization to easily rotate because of a rather flat energy landscape and thus small energy barriers to overcome (see Fig. 3).…”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…194 Since then, other similar BT-based materials were shown to possess exceptional properties. 195,[262][263][264][265] Although BT-based materials have attracted attention in the community recently, their use is limited to low temperatures. So far, chemical modifications and a controlled microstructure led to a maximum ~ 160 °C on this family of materials.…”