Domain structures and local switching in lead-free piezoceramics Ba0.85Ca0.15Ti0.90Zr0.10O3

Abstract

Lead-free piezoelectrics are becoming increasingly important in view of environmental problems of currently used lead-based perovskites such as lead zirconate titanate (PZT). One of the recent candidates for PZT replacement, solid solutions of BaZr 0.2 Ti 0.8 O 3 and Ba 0.7 Ca 0.3 TiO 3 , are investigated in this work by piezoresponse force microscopy. Coexistence of the tetragonal and rhombohedral phases in this material is observed, which probably gives rise to easy polarization switching due to multiple domain states. The period of observed domain lamella scales with the grain size obeying well-known square root dependence characteristic of BaTiO 3 ceramics. Domain switching and relaxation are investigated at the nanoscale as a function of the applied voltage and duration of the applied voltage pulses. The observed distortion of piezoresponse hysteresis loops near grain boundaries is attested to the increased concentration of defects. Nanoscale piezoelectric properties of these materials are discussed. V C 2015 AIP Publishing LLC.

Phenomenological modeling of phase transitions and electrocaloric effect in Ba(Zr0.2Ti0.8)O3‐(Ba0.7Ca0.3)TiO3

“…This phenomenon has not been reported in BZT‐ x BCT relaxor and may seem to contrast with the experimental investigations performed so far in ceramics that indicate no clear trend of Δ T max with varying composition. However, one should note that some discrepancies exist among experiments in BZT‐ x BCT, which may be related to complex microstructures near the MPB and tricritical (or quadruple) point. As pointed out by Bai et al there exists a local EC maximum near the quadruple point ( x ~0.3).…”

“…Later on orthorhombic (O) phase was discovered at the R‐T phase boundary within a narrow composition/temperature range and the C‐T‐O‐R sequence of phase transition was verified by other groups as well . A lot of efforts have been made to procure more data on the phase diagram, polarization states, and microstructures of BZT– x BCT, but there are still some controversies near the phase boundary (particularly the convergence region) …”

Low temperature sintering and dielectric properties of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3−xCu2+ ceramics obtained by the sol-gel technique

“…In electroceramics, the grain boundaries are normally more insulating and capacitive than grains (bulk) mainly due to the presence of dangling bonds and non-stoichiometric distribution of oxygen on the grain boundaries, which act as barrier layers and charge carrier traps [31] . The response of the grain boundaries lies generally at higher frequencies than electrodesemiconductor contacts but lower than the grains (bulk) [31,32] . The complex impedance plot of BCZT-xCu 2+ ceramics with different Cu 2+ additions at 380 °C are shown in Fig.…”

Polarization Domain Dynamics of Barium Titanate Ultrathin Films Using Piezoresponse Force Microscopy.

“…There have been several recent studies of ferroelectric polarization domain formation under an applied electric field [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] , many of which have focused on the application of piezoresponse force microscopy (PFM) to both form and probe polarization domains [6][7][8][9][10][11][12][13][14][15] . In the PFM technique, the tip of an atomic force microscope (AFM) makes contact with a thin film at a specific point and applies an electric potential across a thin film using the AFM tip as one electrode and the back side of the sample as the second electrode (Fig.…”

“…The electric field in the region just beneath the tip is nearly perpendicular to the thin film surface, except for fringing electric field effects. Under the force of the applied electric field, the ferroelectric dipoles align in a direction dependent on the field direction and crystal orientation, resulting in the formation of aligned dipoles directly under the AFM tip [6][7][8][9][10][11][12][13][14][15] . This is observed using the PFM to scan over the thin film which measures and maps out the polarization perpendicular to the surface.…”