phase boundary and electrical properties of lead-free (1-x)BaTi[O.sub.3]-xBi([Li.sub.1/3][Ti.sub.2/3) [O.sub.3] ceramics," Journal of Applied Physics, vol.
region exists on the T-x phase diagram around x [approximately equal to] 0.35 wherein several phases can come about: the cubic, pseudo-cubic, tetragonal, and rhombohedral .
Relaxor based ferroelectric single crystals, such as Pb([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-xPbTi[O.sub.3] (PMNT or PMN-xPT) and Pb([Zn.sub.1/3][Nb.sub.2/3])[O.sub.3]-xPbTi[O.sub.3] (PZNT or PZN-xPT), have ultrahigh electromechanical coupling factor [k.sub.33] (>94%) and piezoelectric constant [d.sub.33] (>2500 pC/N) near the morphotropic
phase boundary at room temperature [5-9].
Hoffmann, "Temperature dependence of poling strain and strain under high electric fields in LaSr-doped morphotropic
PZT and its relation to changes in structural characteristics," Acta Materialia, vol.
This theory is supported by the observations of intermediate phases near the morphotropic
phase boundary (MPB), for example, monoclinic [M.sub.A] and [M.sub.C] phases (space group Cm and Pm, resp.) .
Cann, "The morphotropic
phase boundary and dielectric properties of the xPb([Zr.sub.1/2][Ti.sub.1/2])O3-(1-x)Pb([Ni.sub.1/3][Nb.sub.2/3])[O.sub.3] perovskite solid solution," Journal of Applied Physics, vol.
Ren, "Elastic, piezoelectric, and dielectric properties of Ba([Zr.sub.0.2][Ti.sub.0.8])[O.sub.3]-50 ([Ba.sub.0.7][Ca.sub.0.3])Ti[O.sub.3] Pb-free ceramic at the morphotropic
phase boundary," Journal of Applied Physics, vol.
It is used on a wide scale mainly due to its unique properties at the morphotropic
phase boundary (MPB), at a composition where the PZ: PT ratio is almost 1: 1.
In particular, knowledge of cation off-center displacements in perovskites, which depend on the local chemical environment, enables the prediction of Curie temperature, relaxor dispersion, and the location of morphotropic
phase boundaries--all of which have major impacts on the functional performance of ferroelectrics.
The most interesting for application is the ([K.sub.0.5][Na.sub.0.5])Nb[O.sub.3] compound on the morphotropic
phase boundary [1-3] the ferroelectric phase transition (PT) in which proceeds at [T.sub.c] [approximately equal to] 670 K.
On the morphotropic
phase boundary at x = 0.18, the lattice parameters and unit cell volume change by jump .