Nanoscale Insight Into Lead‐Free BNT‐BT‐xKNN

Abstract

Piezoresponse force microscopy (PFM) is used to afford insight into the nanoscale electromechanical behavior of lead‐free piezoceramics. Materials based on Bi1/2Na1/2TiO3 exhibit high strains mediated by a field‐induced phase transition. Using the band excitation technique the initial domain morphology, the poling behavior, the switching behavior, and the time‐dependent phase stability in the pseudo‐ternary system (1–x)(0.94Bi1/2Na1/2TiO3‐0.06BaTiO3)‐xK0.5Na0.5NbO3 (0 <= x <= 18 mol%) are revealed. In the base material (x = 0 mol%), macroscopic domains and ferroelectric switching can be induced from the initial relaxor state with sufficiently high electric field, yielding large macroscopic remanent strain and polarization. The addition of KNN increases the threshold field required to induce long range order and decreases the stability thereof. For x = 3 mol% the field‐induced domains relax completely, which is also reflected in zero macroscopic remanence. Eventually, no long range order can be induced for x >= 3 mol%. This PFM study provides a novel perspective on the interplay between macroscopic and nanoscopic material properties in bulk lead‐free piezoceramics.

Ferroelectric domain structure of anisotropically strained NaNbO3 epitaxial thin films

“…Since amplitude and phase images of the LPFM and VPFM measurements exhibit no contrasts and nearly no domain-related features are discernible, we do not show the PFM measurements on 10 nm thin films here. The absence of any contrasts in PFM measurements also has been observed in literature for Bi 1/2 Na 1/2 TiO 3 -BaTiO 3 derived ceramics 43 and PbMg 1/3 Nb 2/3 O 3 thin films 44 and was attributed to relaxor properties of the samples. It should be noted that the occurrence of an in-plane polar component cannot be explained if the in-plane anisotropy of lattice strain is neglected.…”

“…In relaxors, weakly interacting polar nanometer-size regions are formed, leading to low polarization contrast, uniformly distributed directions of the dipole moments and diffuse domain walls. 44 Similar results have been described for compressively strained BiFeO 3 thin films on LaAlO 3 substrates 47 and Bi 1/2 Na 1/2 TiO 3 -BaTiO 3 ceramics, 43 which exhibit likewise relaxor properties. Ongoing advanced experiments regarding the domain switching after DC poling and relaxation as well as temperature dependent PFM have also suggested relaxor behavior.…”

Dramatic Influence of A-Site Nonstoichiometry on the Electrical Conductivity and Conduction Mechanisms in the Perovskite Oxide Na0.5Bi0.5TiO3

“…[1][2][3][4] The perovskite oxide Na 0.5 Bi 0.5 TiO 3 (NBT) is one of the favoured candidates to replace PZT and various solid solutions with other ferroelectric materials such as BaTiO 3 and K 1-x Na x NbO 3 have been studied both for piezoelectric and high temperature capacitor (dielectric) applications. [5][6][7][8][9][10][11][12][13][14][15][16][17] NBT has a complex crystal structure. [18][19][20][21][22][23][24][25] Early neutron powder diffraction studies proposed NBT to exhibit a rhombohedral (space group R3c) structure at room temperature (RT).…”

Nanoscale phase quantification in lead-free(Bi1/2Na1/2)TiO3−BaTiOGroszewicz1, Breitzke2, Dittmer3 et al. 2014Phys. Rev. BSelf Cite581340View full textAdd to dashboardCite

“…This state features macroscopic polarization and breaking of the cubic average symmetry [5,11,[15][16][17]. While the RF model suggests that this transformation and the formation of macroscopic ferroelectric domains are caused only by reorientation of previously nanometric ferroelectric domains, an additional mechanism is required when PNRs are considered.…”