Browsing by Author "Shih, I.-C."

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E-field-induced polarization rotation in Pb(Mg1/2Nb2/3)1-xTixO3 crystal
(2003) Tu, Chi-Shun; Shih, I.-C.; Schmidt, V. Hugo
A sequence of field-induced phase transformations was observed by means of a polarizing microscope on a (111)-cut single crystal Pb(Mg1/3Nb2/3)0.67Ti0.33O3 at room temperature with an electric field applied along the [111] direction. As electric field increases, polarizations of the rhombohedral R domains whose polar directions are not along [111] rotate first toward a tetragonal T phase associated with 90° domain walls. Then the crystal gradually reaches total optical extinction for all polarizer angles at 12 kV/cm, indicating a single [111] rhombohedral R111 domain with polarization aligned with the electric field. These field-induced phase transformations are irreversible and proceed most likely through MA -type monoclinic distortions, i.e., R→MA→T→MA→R111.
Electric field- and temperature-induced phase transitions in high-strain relaxor-based ferroelectric Pb(Mg1/3Nb2/3)1-xTixO3 single crystals
(2007-12-07) Chien, R.R.; Schmidt, V. Hugo; Tu, Chi-Shun; Wang, F.-T.; Shih, I.-C.; Hung, L.-W.; Luo, H.
As a review, we compare results in electric-field- and temperature-induced phase transitions for four Pb(Mg1/3Nb2/3)1 - xTixO3(PMNT-x) single crystals, namely (001)-cut PMNT-x (x = 24%, 33%, and 40%) and (111)-cut PMNT-33%. Dielectric properties and domain states were measured as functions of temperature and electric field. The hysteresis loops of polarization versus electric field at room temperature were also measured. The intermediate monoclinic phases are essential in bridging higher symmetries while the electric-field- or temperature-induced transitions are taking place. Whether or not a monodomain state can be induced by a dc electric field strongly depends on crystallographic orientation, PbTiO3 content, and temperature.
Phase transformation via a monoclinic phase in relaxor-based ferroelectric crystal (PbMg1/3Nb2/3O3)1-x(PbTiO3)x
(2003-01-24) Tu, Chi-Shun; Schmidt, V. Hugo; Shih, I.-C.; Chien, R.R.
A monoclinic phase is evidenced between rhombohedral and cubic phases in a 〈111〉-cut single crystal (PbMg1/3Nb2/3O3)0.67(PbTiO3)0.33 (PMN-33% PT) from observation of domain structures. Near 360 K the structure begins to distort from the rhombohedral toward the tetragonal phase through monoclinic domains (probably MA type but perhaps MB type). However, the present 〈111〉-cut crystal seems to disfavor the tetragonal phase and persists in the monoclinic phase up to T∼420K, where the cubic phase begins to develop. Temperature-dependent orientations of optical indicatrices of domains indicate polarization rotations within the monoclinic planes. In addition, a previously electric-field-cooled process enhances a long-range transformation.
Phase transitions and domain structures in relaxor-based ferroelectric (PbZn1/3Nb2/3O3)0.915(PbTiO3)0.085 single crystal
(2001) Tu, Chi-Shun; Schmidt, V. Hugo; Shih, I.-C.
Polarization-electric field (P-E) hysteresis loops and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystal (PbZn,/3Nb2/303)0.9~j(PbTi03)o.o~s (PZN-8.5%PT). In order of increasing temperature, PZN- 8.5%PT undergoes successive phase transitions: rhombohedra1 phase (below -375 K) + coex- istence of rhombohedral and tetragonal phases (between -375 and -390 K) --f tetragonal phase (between -390 and -420 K) -+ coexistence of tetragonal and cubic phases (between -420 and -460 K) -+ cubic phase (above -460 K). Phase coexistence suggests an inhomogeneous distribution of Ti4+ concentration in the PZN-8.5%PT crystal.