The grain size effect on the properties of Aurivillius phase Bi_3.15Nd_0.85Ti₃O₁₂ferroelectric ceramics

Abstract

Aurivillius phase, bismuth layer structured ferroelectric Bi(3.15)Nd(0.85)Ti(3)O(12) (BNdT) ceramics with average grain sizes from 90 nm and high densities (>97%) were fabricated by spark plasma sintering. Decreasing grain size produced a diffuse ferro-paraelectric phase transition and a decrease in the Curie point. Compared with BNdT ceramics with grain sizes of micrometre scale, nanograined BNdT ceramics exhibit a depression of the dielectric maximum at the Curie point, enhanced dielectric constant from room temperature to 350 degrees C and dramatically decreased losses. Although ferroelectric switching was greatly inhibited in nanograined ceramics, both ferroelectric and piezoelectric measurements still clearly showed that BNdT ceramics with 90 nm average grain sizes are ferroelectrically switchable. This is the first reported evidence that nanoscale Aurivillius phase ceramics are ferroelectrically active.

Effect of grain size on domain structures, dielectric and thermal depoling of Nd-substituted bismuth titanate ceramics

“…9 However, there have been limited reports on grain size effects in Aurivillius phase ferroelectrics. [10][11][12] Their crystal structures are considerably different from perovskite structure. The difference may result in different grain size effects.…”

“…10 The density of the BNT ceramics was measured by the Archimedes immersion method. The domain structures of BNT ceramics sintered at different temperatures were examined by an atomic force microscope (AFM) (SPA 400, SPI3800N, Seiko Inc. Japan) in piezoresponse mode.…”

“…The estimated average grain size was 90 6 10 nm and 160 6 20 nm for BNT750 and BNT850, and 2011 6 30 nm in length and 307 6 30 nm in thickness for BNT1000. 10 Figure 2 shows the topographic (left column) and piezoelectric force microscopy (PFM) image (right column) of BNT samples sintered at different temperatures. All the measurements were performed on polished surfaces.…”

“…This can be attributed to the fact that fine grained BNT ceramics have larger coercive field, which is related to the freezing effect in fine grained ceramics with higher stresses. 10 391 6 5 C for BNT750, BNT850, and BNT1000, respectively. 10 This can be regarded as a consequence of the fact that internal stresses tend to favor the stabilization of the paraelectric phase by suppressing the spontaneous deformation and spontaneous polarization, resulting in a lower Curie point T c .…”

“…10 391 6 5 C for BNT750, BNT850, and BNT1000, respectively. 10 This can be regarded as a consequence of the fact that internal stresses tend to favor the stabilization of the paraelectric phase by suppressing the spontaneous deformation and spontaneous polarization, resulting in a lower Curie point T c . 28 The d 33 of all ceramics were thermally stable when the annealing temperature was below 0.6T c .…”