Critical Property in Relaxor-PbTiO(3) Single Crystals --- Shear Piezoelectric Response.
ABSTRACT The shear piezoelectric behavior in relaxor-PbTiO(3) (PT) single crystals is investigated in regard to crystal phase. High levels of shear piezoelectric activity, d(15) or d(24) >2000 pC N(-1), has been observed for single domain rhombohedral (R), orthorhombic (O) and tetragonal (T) relaxor-PT crystals. The high piezoelectric response is attributed to a flattening of the Gibbs free energy at compositions proximate to the morphotropic phase boundaries, where the polarization rotation is easy with applying perpendicular electric field. The shear piezoelectric behavior of pervoskite ferroelectric crystals was discussed with respect to ferroelectric-ferroelectric phase transitions and dc bias field using phenomenological approach. The relationship between single domain shear piezoelectric response and piezoelectric activities in domain engineered configurations were given in this paper. From an application viewpoint, the temperature and ac field drive stability for shear piezoelectric responses are investigated. A temperature independent shear piezoelectric response (d(24), in the range of -50°C to O-T phase transition temperature) is thermodynamically expected and experimentally confirmed in orthorhombic relaxor-PT crystals; relatively high ac field drive stability (5 kV cm(-1)) is obtained in manganese modified relaxor-PT crystals. For all thickness shear vibration modes, the mechanical quality factor Qs are less than 50, corresponding to the facilitated polarization rotation.
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ABSTRACT: This review discusses recent advances in understanding origins of large piezoelectric properties in some ferroelectric materials. In particular, it addresses the role of polarization rotation and monoclinic phases. It is suggested that the polarization rotation is an old concept that was proposed more than 30 years ago to explain enhanced properties of Pb(Zr, Ti) O<sub>3</sub> in the morphotropic phase boundary region. It is further demonstrated that in addition to polarization rotation, polarization extension can also lead to large electro-mechanical properties. In fact, the largest piezoelectric coefficient has been reported in KH<sub>2</sub>PO<sub>4</sub>, which exhibits structural instability involving polarization extension and no monoclinic phases. It is also shown that substantial theoretical and experimental evidence exists to show that the highest piezoelectric response is often not observed in monoclinic phases but in the phase transition regions where polarization either changes direction or appears from the nonpolar state. Finally, it is proposed that the concept of free energy instability, which emerged from phenomenological and first principle calculations, is the most general approach that can be used to consistently interpret many experimental observations and underlies many theoretical results on enhancement of piezoelectric properties.IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 09/2009; · 1.69 Impact Factor
Article: Polarization rotation via a monoclinic phase in the piezoelectric 92% PbZn(1/3)Nb(2/3)O3-8% PbTiO3.[show abstract] [hide abstract]
ABSTRACT: The origin of ultrahigh piezoelectricity in the relaxor ferroelectric PbZn(1/3)Nb(2/3)O3-PbTiO3 was studied with an electric field applied along the  direction. The zero-field rhombohedral R phase starts to follow the direct polarization path to tetragonal symmetry via an intermediate monoclinic M phase, but then jumps irreversibly to an alternate path involving a different type of monoclinic distortion. Details of the structure and domain configuration of this novel phase are described. This result suggests that there is a nearby R-M phase boundary as found in the Pb(Ti,Zr)O3 system.Physical Review Letters 05/2001; 86(17):3891-4. · 7.37 Impact Factor
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ABSTRACT: The shear resonance behavior of rectangular-shaped samples of single-domain PZN-PT single crystal samples of 3m symmetry and having three faces parallel to the (111), (112), and (110) crystal planes has been examined. Sample geometries with separable resonance peaks are identified, which give shear properties consistent with 3m symmetry, namely, k15 approximately k24 and d15 approximately d24. Sample geometries with inseparable resonance peaks are also distinguished. The latter sample geometries are not suitable for shear property characterization of piezoelectric single crystals of 3m symmetry as the broad coupled resonance peak often results in inflated k15 and d15 values.IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 12/2007; 54(11):2222-6. · 1.69 Impact Factor