Nanotwins and phases in high-strain Pb(Mg1/3Nb2/3)1−xTixO3 crystal

Abstract

This work is a study of the thermal stability of ͑001͒-cut Pb͑Mg 1/3 Nb 2/3 ͒ 1−x Ti x O 3 ͑x = 0.30͒ single crystals before and after an electric ͑E͒-field poling by means of dielectric permittivity, hysteresis loop, domain structure, polarization current, and x-ray diffraction. An R͑R NT ͒-R͑R NT ͒ / T͑T NT ͒-T͑T NT ͒-C transition sequence was observed upon heating in the unpoled sample. R, R NT , T, T NT , and C are the rhombohedral, rhombohedral nanotwin, tetragonal, tetragonal nanotwin, and cubic phases, respectively. R / T indicates coexistence of the R and T phases. R͑R NT ͒ and T͑T NT ͒ indicate that the R NT and T NT structures mimic monoclinic phases in the R and T matrices, respectively. After a prior E-field poling, an R͑R NT ͒-T͑T NT ͒-C phase sequence takes place upon heating. The dielectric permittivity and current density evidenced an additional polarization at 355 K, which is associated with the vanishing of the dielectric dispersion, which reappears near 410 K and remains up to the Burns temperature T B = 510 K. This study suggests that nanotwins ͑R NT and T NT ͒ can play an important role in high-strain piezoelectric crystals while phase transition takes place. Under E =38 kV/ cm, ͓001͔ T domains randomly appeared in the matrix, suggesting that the matrix consists of a glassy matrix and ferroelectric nanoclusters.

Nanotwin and phase transformation in tetragonal Pb(Fe1/2Nb1/2)1−xTixO3 single crystal

“…Nanotwin structures, which often cause broad XRD spectra, were also evidenced apparently in the ͑001͒ oriented PMN-30%PT crystal. 22 However, the recent in situ temperature-dependent XRD result of the ͑111͒-cut PMN-30%PT crystal did not show obvious imprint of nanotwin structure, implying that the elastic strain energy is smaller in the ͑111͒ oriented rhombohedral crystal. 23 Nanotwin structure seems to play an important role in the ͑001͒ oriented high-strain FE crystals while phase transition takes place because they can accommodate the spontaneous lattice distortion.…”

Temperature dependence of electric-field-induced domain switching in 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single crystal

“…The R–M A phase transformation is predicted to be the minimum energy path of polarization rotation. The irregular shaped microdomains are possibly caused by rotating microdomains or nanocluster polarizations into alignment, which play an important role in PMN–PT single crystals because they can accommodate the spontaneous lattice distortion and minimize the elastic strain energy [23,24]. …”

Origin of high piezoelectric response in A-site disordered morphotropic phase boundary composition of lead-free piezoelectric 0.93(Na0.5Bi0.5)TiO3–0.07BaTiO3

“…62 Furthermore, we believe that higher mobility of these nano twins is responsible for giving rise to high strain energy density in MPB composition of NBT-BT. 63,64 Recently, in-situ TEM experiments under electrical biasing have also shown that in PZN, polarization reversal can occur by reorientation of nanoscale non-180 domain walls between monoclinic nanotwins. 65 The local crystallographic distortions in the MPB composition of NBT-BT can be justified from thermodynamic considerations as explained below.…”