High temperature Aurivillius piezoelectrics: The effect of (Li, Ln) modification on the structure and properties of (Li, Ln)_(0.06)(Na, Bi)_(0.44)Bi_2Nb_2O_9 (Ln = Ce, Nd, la and Y)

摘要

High temperature Aurivillius piezoelectrics, (Li, Ln)_(0.06)(Na, Bi)_(0.44)Bi_2Nb_2O_9 (NBN-LiLn), with Li and Ln (Ce, Nd, La and Y) co-substitution at the A site, were prepared using a solid-state reaction process. Taking cation disordering between A site and the (Bi_2O_2)~(2+) layers into consideration, the crystal structure of (Li, Nd)_(0.06)(Na, Bi)_(0.44)Bi _2Nb_2O_9 (NBN-LiNd) was refined by using the Rietveld method with powder X-ray diffraction, which was confirmed to be a two-layer Aurivillius oxide with an orthorhombic space group, A2_1am a = 5.48666(9) ?, b = 5.46046(8) ?, c = 24.9122(4) ? and Z = 4, at room temperature. LiNd substitution induced a decrease in cation disorder and an increase in orthorhombic distortion. The ferroelectric to paraelectric phase transition temperature (Tc) of the NBN-LiLn (Ln = Ce, Nd, La and Y) ceramics ranged from 751 to 842 °C and the Tc increased as the radii of the Ln~(3+) (Ce~(3+), Nd~(3+), La ~(3+) and Y~(3+)) was decreased. The NBN-LiCe and NBN-LiNd had a d_(33) of 31 and 29 pC N~(-1), respectively, which is much higher than the reported d33 values of other Aurivillius ceramics with a high T_c (T_c > 650 °C, d_(33) < 20 pC N~(-1)). With increasing annealing temperature, a significant degradation in d_(33) was observed for NBN-LiCe, while no drop in d _(33) was observed up to 650 °C for NBN-LiNd. The inhomogeneous domain structures determined the dissimilar piezoelectric behaviors of NBN-LiCe and NBN-LiNd.