Nanoscale Insight Into Lead-Free Piezoceramics

1. CNMS User Project Highlight Nanoscale Insight Into Lead-Free Piezoceramics • Scientific Achievement • Piezoresponse force microscopy (PFM) is employed to provide insight into nanoscopic material properties in bulk lead-free piezoceramics. Usingthe band excitationtechniquetheinitialdomainmorphology, thepolingbehavior, theswitchingbehaviorandthe time-dependentphasestability in the pseudo-ternarysystem (1-x)(0.94Bi1/2Na1/2TiO3-0.06BaTiO3)-xK0.5Na0.5NbO3 (0x18 mol%) arerevealed. • Significance • For the first time the electromechanical behavior of a bulk lead-free piezoceramic is comprehensively studied on the nanoscale and compared with macroscopic sample properties. This knowledge will help to tailor lead-free materials for specialized applications. • Research Details • CNMS Capability: Band excitation PFM allows imaging ferroelectric domains and enables local measurement of pizeoresponse hysteresis loops • A locally applied bias can induce long-range order, which is the key for the development of high strains • The switching voltage drastically increases with K0.5Na0.5NbO3 (KNN) mole fraction and a bias-induced long-range order cannot be induced in the material for KNN high content. • Long-time relaxation measurements revealed the influence of the KNN content on the relaxation process, perfectly rationalizing the observation of decreasing remanence in macroscopic polarization measurements with x. 0%KNN 1%KNN 3%KNN 9%KNN 18%KNN Poling behavior as function of KNN content after poling with ∓ 20 V of 3x3 µm² and 1x1 µm²regions, respectively. The color in the displayed 5x5 µm² PFM images indicates the domain orientation after poling (red = down, blue = up). Addition of KNN clearly impedes formation of domains and switching thereof under electric field. Robert Dittmer, Wook Jo, Jürgen Rödel, Sergei Kalinin, Nina Balke Adv. Funct. Mater. DOI: 10.1002/adfm.201200592 (2012).