Temperature dependence of polarization and strain in Bi0.5Na0.5TiO3-SrTiO3 multilayer composites

Relaxor-ferroelectric phase transition materials exhibit excellent strain behavior under applied electric fields for utilization in actuator applications. However, the large strain of relaxor-ferroelectric phase transition materials can only be achieved in a narrow temperature range. Hence, in this study, composition-based multilayer samples and compositional gradient composite (CGC) samples were designed and fabricated to extend the usable temperature range of relaxor-ferroelectric materials. The raw materials used were 0.78(Bi0.5Na0.5TiO3)-0.22SrTiO(3) and 0.72(Bi0.5Na0.5TiO3)-0.28SrTiO(3). The multilayered sample containing two ceramics showed higher temperature-dependent strain and polarization than those of the single-composition ceramic. In addition, phase transition was observed in the CGC in the low- and high-temperature ranges. In the CGC sample, the compositional gradient characteristics of Sr were observed along the vertical direction owing to diffusion. This reduced the temperature-dependent unipolar strain of the sample (0.148-0.175%) in the range of -20 degrees C < T < 100 degrees C. This behavior can be attributed to the combined effect of the relaxor-ferroelectric phase transition and ferroelectric domain reorientation, as well as the relaxor electrostriction. The sintering temperature had a significant effect on the compositional gradient of Sr and the performance of the layered composites. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

By designing and fabricating multilayer samples and compositional gradient composite samples, the usable temperature range of relaxor-ferroelectric materials was extended, showing higher temperature-dependent strain and polarization. The compositional gradient led to the combined effect of relaxor-ferroelectric phase transition and ferroelectric domain reorientation, reducing the temperature-dependent unipolar strain of the samples.