Ergodicity of fine‐grained canonical relaxor ferroelectric (Bi_0.5Na_0.5)_1‐xBa_xTiO₃ films

Abstract

The drastic reduction in dimensions in thin films, together with the low crystallization temperatures used, normally results in a large reduction in the grain size. It has been reported that relaxor ferroelectric states are stabilized at room temperature for fine‐grained ceramics and films that behave as normal ferroelectrics for large grains. In this work, the effects of the grain size reduction on the relaxor characteristics are analyzed for a composition that is already a canonical relaxor with a nonergodic state at room temperature: (Bi0.5Na0.5)1‐xBaxTiO3 (BNBT). The comparison of the local polar ordering within BNBT grains studied with piezoresponse force microscopy on large‐grained ceramics and fine‐grained thin films shows that the development of stable long‐range ferroelectric order with the application of an electric field is hampered due to the small grain size of the grains. The ergodic character of the high‐temperature phase is thus stabilized at room temperature, following a similar mechanism as the one discussed for other noncanonical relaxors.

Stress-mediated solution deposition method to stabilize ferroelectric BiFe1-xCrxO3 perovskite thin films with narrow bandgaps

“…The topography images of both films indicate similar size of their grains (Figures 7a and 7b), which are all piezoelectric according to the out-of-plane amplitude (Figures 7c and 7d) and phase (Figures 7e and 7f) PFM images. [31,59] A larger porosity is observed in the topography image of the HP 25-BFCO film, in agreement with the FEGSEM and EDX results of Figure 6. Regions of the film surfaces without piezoresponse, which would be representative of secondary non ferroelectric phases, are not observed by PFM.…”

Enhanced thermal stability by short-range ordered ferroelectricity in K0.5Na0.5NbO3-based piezoelectric oxides

“…28 Yet others have reported that a large ratio of grain boundaries with low permittivity can be attributed to relaxor behavior in fine grains. 29 In this work, we studied the effect of grain size on polar configuration and thermal stability at the nanoscale through phase-field simulations and first-principles calculations. Based on computational prediction, we synthesized a set of KNN-based ceramics via meticulous segmentation of the BiScO 3 (BS) doping concentration near the chemical composition where abnormal grain growth exists.…”

“…28 Yet others have reported that a large ratio of grain boundaries with low permittivity can be attributed to relaxor behavior in fine grains. 29…”