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Temperature- and electric (E)-field-dependent domain structures and phase transformations in a (001)-cut Pb(Mg1/3Nb2/3)0.6Ti0.4O3 (PMNT40%) single crystal have been investigated by polarizing microscopy and dielectric permittivity. The unpoled crystal has tetragonal phase domains (15–60 μm wide) with polarizations along [100] and [010], which are separated by 90° domain walls. They coexist with a small fraction of the monoclinic phase domains near 200 K. The tetragonal domains increase rapidly at the expense of the monoclinic domains as the temperature increases toward room temperature. This may account for the steplike dielectric anomaly in [variant_greek_epsilon]′ from around 280 K. The whole crystal reaches the cubic phase near 464 K. The E-field-dependent domain structures at room temperature show a significant change near 11 kV/cm when the polarizations rotate to the tetragonal [001] (T001) direction through the monoclinic phase. Microcrackings begin to develop near 12.5 kV/cm. The entire crystal becomes T001 monodomain near 33 kV/cm. After the E field is removed, the crystal does not reestablish the T100 and T010 macrodomains, but instead breaks up into tetragonal microdomains. [ABSTRACT FROM AUTHOR]

Dielectric properties and domain structure have been measured as functions of temperature in a (001)-oriented Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMNT35%) single crystal with and without a prior dc electric (E)-field poling. Without E-field poling, the dielectric loss exhibits a frequency-dependent maximum in the region of 120–180 K, which can be described by a Vogel–Fulcher equation and fractal cluster model which implies structural irregularities within domains. With a prior poling a long-range monoclinic (tetragonal)→tetragonal (monoclinic) transition takes place near 212 K upon heating. “Monoclinic (tetragonal)” represents that dominant monoclinic phase domains coexist with a small fraction of tetragonal phase domains. Optical transmission and birefringence were significantly enhanced by a prior E-field poling. The Cauchy equations for ordinary no and extraordinary ne refractive indices were determined between 0.45 and 1.4 μm. However, the phase-matching criterion for second-harmonic generation was not found. [ABSTRACT FROM AUTHOR]

Polarization rotations of temperature- and electric-field-dependent phase transformations in a (211)-cut Pb(Mg1/3Nb2/3)0.69Ti0.31O3 (PMNT31%) single crystal were observed by means of polarizing microscopy. Dielectric permittivity was also measured as a function of temperature and frequency. Below 380 K domains are mostly rhombohedral (R) phase mixed with monoclinic (M) domains. As temperature increases above 380 K, polarizations of the rhombohedral domains begin to rotate toward the cubic (C) phase through monoclinic distortions, i.e., R→M→C, associated with a long-range percolation of monoclinic phase near 380 K. However, the tetragonal phase was not observed apparently. Electric-field-dependent domain structures show that a long-range R→M phase transformation takes place in the range of 3–5 kV/cm as electric field increases. The crystal cannot reach a monodomain as the electric field reaches 26 kV/cm. A hysteresis loop of polarization versus electric field was also measured for comparison with electric-field-dependent observation of polarizing microscopy. [ABSTRACT FROM AUTHOR]

Dielectric permittivities, Brillouin backscattering spectra, polarization-electric field hysteresis loops, and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystals (PbMg[sub 1/3]Nb[sub 2/3]O[sub 3])[sub 1-x](PbTiO[sub 3])[sub x](PMN-xPT) for x=0.24 and 0.34. For PMN-24%PT, a diffuse phase transition which is associated with a broad frequency-dependent dielectric maximum was observed near 380 K. As the temperature increases, the PMN-24%PT crystal gradually develops cubic regions and is fully converted into the cubic state near 375 K. An extra dielectric anomaly appears at 370 K, possibly due to the percolating polar cluster induced by an external electric field. PMN-34%PT exhibits a nearly normal ferroelectric phase transition near 445 K from the tetragonal to the cubic phase. In addition, a weak diffuse phase transition observed near 280 K may result from partial conversion of rhombohedral phase to tetragonal phase. The dielectric thermal hysteresis confirms that the transitions near 280 and 445 K are diffuse first order and first order, respectively. The dielectric permittivities of PMN-24%PT and PMN-34%PT obey the relation, ε[sub m][sup ′]/ε[sup ′](f,T)=1+[T-T[sub m](f )][sup γ]/2δ[sub γ][sup 2], above the temperature of permittivity maximum T[sub m]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined the hypersonic and dielectric properties of lead zinc niobate-lead titanate single crystal. Experimental procedure; Results and discussion of the study.

Deals with a study which measured the longitudinal and transverse vibrational modes as a function of temperature for both KTiOPO[sub4] and KTiOAsO[sub4] single crystals. Background to the structure; Experimental procedure; Results and discussion.