The field induced e31,f piezoelectric and Rayleigh response in barium strontium titanate thin films

Abstract

The electric field induced e 31,f piezoelectric response and tunability of Ba 0.7 Sr 0.3 TiO 3 (70:30) and Ba 0.6 Sr 0.4 TiO 3 (60:40) thin films on MgO and silicon was measured. The relative dielectric tunabilities for the 70:30 and 60:40 compositions on MgO were 83% and 70%, respectively, with a dielectric loss of less than 0.011 and 0.004 at 100 kHz. A linear increase in induced piezoelectricity to À3.0 C/m 2 and À1.5 C/m 2 at 110 kV/cm was observed in Ba 0.6 Sr 0.4 TiO 3 on MgO and Ba 0.7 Sr 0.3 TiO 3 on Si. Hysteresis in the piezoelectric and dielectric response of the 70:30 composition films was consistent with the positive irreversible dielectric Rayleigh coefficient. Both indicate a ferroelectric contribution to the piezoelectric and dielectric response over 40-80 C above the global paraelectric transition temperature. V C 2014 AIP Publishing LLC.

Nonlinear dynamics of polar regions in paraelectric phase of (Ba1-x,Srx)TiO3 ceramics

“…A similar idea was also proposed by Garten et al for BST thin films and ceramics. 10,12,17,50 They demonstrated that a strain gradient may polarize BST samples and suggested that it happens by the reorientation of residual ferroelectric domains (or another kind of polar entities) whose dynamics can be described by Eq. (1).…”

“…22,23 The experimental values of the flexoelectric coefficients in this solid solution cannot be reconciled easily with theoretical predictions. [24][25][26][27] Garten et al 10,12,17,28 proposed that in their BST thin films and ceramics, the flexoelectric polarization in the paraelectric phase is enhanced by polarization from residual ferroelectric domains (or microdomains or micropolar regions), leading to exceptionally large apparent flexoelectric coefficients. A similar result was reported by Narvaez and Catalan for the flexoelectric response in the paraelectric phase of a single crystal relaxor-ferroelectric.…”

“…12 The macroscopic polarization was explained by a stress-gradient induced alignment of polar entities. The increase in the permittivity in BST films and ceramics with the increasing amplitude of the alternating (ac) electric field was interpreted 10,12,17 in terms of the Rayleigh-type dynamics 29,30 of residual domain walls (or another type of interfaces). Interestingly, the macroscopic polarization reported in the paraelectric phase of BST in Ref.…”

“…The physics and chemistry of the local polar entities are not fully understood although their contribution to the properties may be significant or even dominant. Examples include the large and frequency dispersive dielectric permittivity in relaxors, [13][14][15] the large piezoelectric effect above $150 K in relaxor-ferroelectrics, 4 the flexoelectric coupling in relaxor-ferroelectrics, 10,12,16,17 and the macroscopic polarization in nominally nonpolar phases observed in ferroelectric materials. 18 In this paper, we address the effects of short-range polar entities on the nonlinear polarisation response in the paraelectric phase of the (Ba 1-x ,Sr x )TiO 3 (BST) solid solution.…”

Relaxor Ferroelectric Behavior in Barium Strontium Titanate

“…As a result, current research efforts have focused on increasing film quality as a means to improve the tunable figure of merit (FOM) . However, other routes exist to further improve FOM values in BST, such as reducing the residual ferroelectric and piezoelectric loss contributions, which are less widely addressed …”