Ferroelectric phase transitions in multi-domain K_0.9Na_0.1NbO₃ epitaxial thin films

Abstract

Ferroelectric phase transitions in multi-domain K 0.9 Na 0.1 NbO 3 epitaxial thin films To cite this article: Laura Bogula et al 2020 Nano Futures 4 035005 View the article online for updates and enhancements.

Temperature dependence of three-dimensional domain wall arrangement in ferroelectric K0.9Na0.1NbO3 epitaxial thin films

“…This also concerns the predicted coexistence of a 1 a 2 and a 1 /a 2 phases at high temperatures. However, in our recently published study, 25 grazing in-plane x-ray diffraction revealed that heating up to 180 °C leads to a complete disappearance of the M C phase, while the a 1 a 2 phase can always be observed. In addition, the monoclinic a 1 a 2 and the orthorhombic a 1 /a 2 phases coexist between about 200 °C and 220 °C.…”

“…However, for reasons of symmetry and x-ray measurements discussed below, we expect a similar stripe domain pattern with domain walls rotated by ξ = +45°. In a recently published paper, 25 we have shown that the stripe domain pattern consists of slightly rotated orthorhombic unit cells, finally leading to an a 1 /a 2 domain arrangement with exclusive horizontal electrical polarization. For more detailed information about the unit cell symmetry and structural properties of the high-temperature phase, we refer the reader to Ref.…”

“…For more detailed information about the unit cell symmetry and structural properties of the high-temperature phase, we refer the reader to Ref. 25.…”

“…Having discussed the room temperature ferroelectric phase and the high-temperature ferroelectric phase separately in the previous chapters, we now want to focus our attention on the extended temperature range within which the phase transition takes place and in which we have experimentally observed a coexistence regime between different ferroelectric phases. 25 For this reason, phase-field simulations were performed using a preset herringbone domain arrangement at equilibrium at room temperature, see Fig. 5(a) [replotted the same figure here as in Fig.…”

“…Lattice strains determine not only the phase symmetry and domain wall arrangement in epitaxial films but also have a crucial influence on phase transitions. In a previous paper, 25 we have revealed that K 0.9 Na 0.1 NbO 3 thin films on NdScO 3 (NSO) substrates undergo a ferroelectric-to-ferroelectric phase transition at high temperatures. The phase transition transforms a complex herringbone-like domain pattern with an alternating monoclinic a 1 a 2 /M C domain arrangement 26 to an orthorhombic phase, which appears as a very regular a 1 /a 2 stripe domain pattern that occurs in four different variants of superdomains.…”