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The crystallographic dependence of the DC electric (E) field induced strain and phase transition in Na0.5Bi0.5TiO3-5.6%BaTiO3 (NBT-5.6%BT) single crystals has been investigated. An induced transition between pseudocubic and tetragonal structures was observed under E = 10 kV/cm for fields applied along the < 001 > direction, whereas an induced transition between pseudocubic and rhombohedral structures was observed when the E-field was applied along < 111 >. Our results show near the morphotropic phase boundary that the phase stability of NBT-x%BT is dependent on the crystallographic direction along which E was applied. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757877] National Science Foundation (Materials World-Wide Network) DMR-0806592 Natural Science Foundation of China 50602047 Shanghai Municipal Government 08JC1420500 Innovation Fund of Shanghai Institute of Ceramics Y09ZC4140G Ministry of Science and Technology of China through 973 Program 2009CB623305

The ferroelectric domain and local structures of Na0.5Bi0.5TiO3-xat.%BaTiO3 (NBT-x%BT) crystals for x = 0, 4.5, and 5.5 have been investigated by transmission electron microscopy. The results show that the size of polar nano-regions was refined with increasing xat. %BT. The tetragonal phase volume fraction, as identified by in-phase octahedral tilting, was found to be increased with BT. The findings indicate that the large electric field induced strains in morphotropic phase boundary compositions of NBT-x%BT originate not only from polarization rotation but also polarization extension. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673832] National Science Foundation (Materials World Network) DMR-0806592 Department of Energy DE-FG02-07ER46480 National Science Foundation of China 50602047 Shanghai Municipal Government 08JC1420500 China Scholarship Council

The ferroelectric domain and local structures of Na1/2Bi1/2TiO3-x% BaTiO3 (NBT-BT) and 0.14 at. % Mn substituted Na1/2Bi1/2TiO3-x% BaTiO3 (Mn:NBT-BT) single crystals with x=5.5 near a morphotropic phase boundary have been investigated by transmission electron microscopy. Increased ferroelectric ordering and enhanced in-plane octahedral tilting were observed for Mn: NBT-BT compared with NBT-BT. Bragg-filtered lattice images revealed that the size of the in-phase tilt domains of Mn:NBT-BT were on the order of 2 to 8 nm, with a tendency of alignment along {110}. (C) 2011 American Institute of Physics. [doi:10.1063/1.3573801] National Science Foundation (Materials World Network)_DMR-0806592 Department of Energy DE-FG02-07ER46480 National Science Foundation of China 50602047 Shanghai Municipal Government 08JC1420500 China Scholarship Council

We report on the observation of an orthorhombic ferroelectric phase in 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 single crystals, whose polarization is along 〈011〉 direction and stability can be altered by poling conditions. We studied the piezoelectric properties on poled 〈011〉 crystals, in both monodomain and polydomain states, and found that the piezoelectric d32 coefficient, which is the piezoelectric response in perpendicular to the poling direction, is positive in both cases. Based on the phenomenological theory, we show that this is possible in a crystal with the electrostrictive coefficients Q11>Q44–Q12.

Mn-doped Na0.5Bi0.5TiO3-5.6 at. %BaTiO3 (Mn:NBT-5.6% BT) single crystals were grown by a top-seeded solution growth method. Tetragonal and rhombohedral phases were found to coexist in the as-grown condition. The dielectric and structural properties were studied as a function of temperature under dc electrical bias. An induced phase stability change from rhombohedral to tetragonal phases occurred under an electric-field applied along the < 001 > direction. (C) 2009 American Institute of Physics. [doi:10.1063/1.3253412] National Science Foundation DMR0806592 Department of Energy DE-FG02-07ER46480 Natural Science Foundation of China 50602047 Shanghai Municipal Government 08JC1420500

The structural, dielectric, and piezoelectric properties of Na0.5Bi0.5TiO3-x mol. %BaTiO3 (NBT-x%BT) crystals have been investigated. The dielectric and piezoelectric properties of NBT-x%BT were enhanced near x = 5–7. High resolution synchrotron x-ray powder diffraction studies revealed the presence of a phase boundary between monoclinic (Cc) and tetragonal (P4bm) phases near x = 5–7, where the dielectric and piezoelectric properties were enhanced.

Diffuse scattering and relaxor behavior in Na0.5Bi0.5TiO3 (NBT) and NBT-5.6 at. %BaTiO3 (NBT-5.6%BT) were investigated. X-ray diffraction revealed two types of diffuse scattering in NBT: (i) broad and (ii) asymmetric L-shaped. After modification with 5.6%BT, the broad diffuse scattering patterns became narrow, and the asymmetric L-shaped ones were replaced by symmetric ones. The symmetric diffuse scattering in NBT-5.6%BT disappeared with increasing dc electric field (E) for E ≥ 9.5 kV/cm where the frequency dispersion in the dielectric constant disappeared. These results demonstrate that the relaxor characteristics are directly correlated with the diffuse scattering and the presence polar nano-regions.

Optical properties of A-site disordered Na0.5Bi0.5TiO3-x%BaTiO3 (NBT-xBT) single crystals with three typical compositions were studied systematically. Refractive index as a function of wavelength was measured by Spectroscopic ellipsometry, and modified Sellmeier dispersion equations were obtained by the least square fitting. High optical transmittance (65%) over a wide transparent region (from 400 to 6000 nm) has been found in NBT-7.5BT, much higher than that of NBT and NBT-5BT. Optical band gap energies were calculated using the absorption coefficient through Tauc equation. With increasing BT content, refractive index and absorption coefficient decrease, while transmission and band gap energy increase.

In present work, lead-free single crystal 0.94Na1/2Bi1/2TiO3–0.06BaTiO3 (NBBT94/6) with dimension of Φ40 mm×10 mm was grown by a precisely controlled top seeded solution growth method. The crystal structure measurement result indicates that the NBBT94/6 single crystal exhibits the feature of rhombohedral-tetragonal phase coexistence at room temperature. The crystallographic orientation dependence of electrical properties for NBBT94/6 single crystal was investigated in detail. The remnant polarizations (Pr) of ⟨001⟩, ⟨001⟩, and ⟨111⟩ oriented crystals are 16.02 μC/cm2, 22.16 μC/cm2, and 27.23 μC/cm2, respectively. The corresponding coercive fields (Ec) are 24.89, 20.72, and 15.36 kV/cm. Moreover, a double hysteresis loop appears at the depolarization temperature. High piezoelectric properties d33 of 360 pC/N and kt of 62% were obtained in the ⟨001⟩ oriented crystals due to the engineered domain configuration which make them promising candidates for environmental friendly solid-state actuator applications.

The ferroelectric domain structure of Na1/2Bi1/2TiO3 single crystals was investigated by transmission electron microscopy (TEM) and piezoforce microscopy (PFM). Bright-field TEM and PFM images revealed the presence of polar nanodomains, whose boundaries had a tendency to align along the ⟨110⟩. High resolution TEM images revealed planar defects along these ⟨110⟩ boundaries, which partially relaxed the coherency of the lattice.

A systematic study of the optimized orientation and temperature dependence of shear-mode piezoelectric properties for ternary Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT or PIMNT) piezocrystals was carried out. It was found that [111]-poled samples presented the best shear piezoelectric properties when driving along [11¯0] (the thickness direction). The electromechanical coupling coefficient k15 and piezoelectric coefficient d15 and g15 were found to be 96.4%, 5966 pC/N, and 0.047 Vm/N, respectively, for optimum-cut samples with platinum (Pt) electrode. Besides, the maximum service temperature for shear mode is around 105 °C, which is much higher than PMNT single crystals.

In this letter we presented a cantilever beam used for vibration energy harvesting based on shear mode 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 single crystal. The working principle of the device was inferred and the factors influencing the output were obtained using an analytical method. The electrical properties under different conditions were studied systematically. Under a cyclic force of 0.05 N (peak value), a peak voltage of 91.23 V, maximum power of 4.16 mW were measured at 60 Hz with a proof mass of 0.5 g. The results demonstrate the potential of the device in energy harvesting applied to low-power portable electronics and wireless sensors.

High piezoelectric and ferroelectric properties have been found in Mn-doped Na0.5Bi0.5TiO3-BaTiO3 single crystals, which were grown by a top-seeded solution method. The electrical resistivity, dielectric constant, and ferroelectric and piezoelectric properties were all found to be notably enhanced by Mn. The piezoelectric constant d(33) and electromechanical coupling coefficients k(t) and k(31) were found to be as high as 483 pC/N, 0.56, and 0.40, respectively. These values are much higher than those previously reported for Pb-free piezoelectric crystals, demonstrating the real potential for alternative lead-free systems for sensor and piezoelectric applications. Ministry of Science and Technology of China_2008AA03Z410, 2009CB623305 Natural Science Foundation of China 60837003, 50777065, 50602047 Shanghai Municipal Government 08JC1420500 Innovation Fund of Shanghai Institute of Ceramics SCX0608 Fund of National Engineering Research Center for Optoelectronic Crystalline Materials 2005DC105003, 2007K05 National Science Foundation DMR-0806592 U. S. Department of Energy DE-FG02-07ER46480