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The effect of uniaxial compression stress on the phase/domain pattern and the electromechanical performances were investigated for Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN–PMN–PT) ferroelectric crystals by the polarization/strain vs. electric field and strain vs. uniaxial stress curves measurement. The results showed that (1) uniaxial stress could induce the rotation of polarization from [101]c, [011]c, [−101]c and [0–11]c directions to [110]c, [−110]c, [−1–10]c and [1–10]c directions but no phase transition in orthorhombic (O) phase PIN–PMN–PT crystal; (2) the dielectric and piezoelectric responses of O phase crystal were found to be enhanced by 6.5% and 15% respectively in the region of domain switching due to the increase of free energy instability and polarization mobility induced by uniaxial stress.

The charge release and related mechanisms for Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN–PMN–PT) ferroelectric crystals under one-dimensional shock wave compression were investigated using discharge current profile measurement, by which the piezoelectric stress coefficient e31 and the phase transition (from tetragonal to orthorhombic phase) pressure were obtained, being −2.9 C/m2 and 2.3 GPa, respectively. Based on experiment results and thermodynamics analysis, it was found that the one-dimensional shock compression favored ferroelectric phase, being different from the effect of hydrostatic pressure, which favored paraelectric phase. This phenomenon can be attributed to the crystal anisotropy and electromechanical coupling effects as one-dimensional shock compression is applied to PIN–PMN–PT ferroelectric crystals.

The effects of hydrostatic and one-dimensional (1D) compression pressure on the phase transition of perovskite ferroelectric crystal were comparably investigated via the measurement of polarization P r with respect to applied pressure and the Landau–Devonshire (LD) phenomenological approach. The results showed that hydrostatic pressure can induce ferroelectric-to-paraelectric phase transition, while 1D compression can stablize the ferroelectric phase. This phenomenon was very different from the phase transitions of metal crystals, such as iron. In the framework of LD phenomenological theory, this phenomenon is believed to be associated with the strong anisotropy and electromechanical coupling which exists in ferroelectrics under high pressure. On the other hand, the piezoelectric stress coefficient e 31 and piezoelectric strain coefficient d h for PIN-PMN-PT crystal were obtained as −2.9 C m−2 and 80 pC N−1, respectively.

Ferroelectric phase transitions and electromechanical properties of BaTiO3 (BT) and PbTiO3 (PT) crystals under one-dimensional shock wave compression were investigated using Landau-Ginzburg-Devonshire phenomenological approach. The results showed that the Curie temperature of both BT and PT increased with increasing pressure. Under highest shock wave compression, the orthorhombic phase was the stable state for BT, while no ferroelectric-ferroelectric phase transition was induced for PT. At room temperature, the electromechanical parameters for PT and BT were found to decrease with increasing one-dimensional compression, except for the dielectric susceptibility e22 and piezoelectric coefficient e24 of tetragonal BT. The variations of dielectric and piezoelectric parameters were analyzed according to the elastic Gibbs free-energy.

The hydrostatic piezoelectricity of Pb ( Mg 1/3 Nb 2/3)–x PbTiO 3 (PMN–xPT) ceramics and PMN–0.32PT and Pb(Mg1/3Nb2/3)–Pb(In1/2Nb1/2)–PbTiO3 (PMN–PIN–PT) crystals were investigated through a quasi-static method. The results showed that pressure-induced depolarization occurred in PMN–xPT ceramics when pressure was above about 50 MPa, while there was no obvious pressure-induced depolarization for PMN–0.32PT and PMN–PIN–PT crystals in the whole pressure range (0~530 MPa). The hydrostatic piezoelectric coefficient d h of PMN–0.32PT and PMN–PIN–PT crystals was nearly independent of pressure. The d h of mono-domain orthorhombic and tetragonal phase crystals is slightly larger, on the order of 100 pC/N. In addition, the relationship between the hydrostatic piezoelectric coefficient d h and the longitudinal and transverse piezoelectric coefficients d33 and d31 for different crystal systems was summarized.

The electromechanical properties of rhombohedral single crystals Pb(Mg1/3Nb2/3)-Pb(In1/2Nb1/2)-PbTiO3 (PMN-PIN-PT) were investigated under hydrostatic pressure from 0.1 to 456 MPa. Due to pressure-induced morphotropic phase boundary moving, the piezoelectric coefficients and electromechanical coupling factors of PMN-PIN-PT crystals were found to decrease by ∼10% and ∼2%, respectively. The mechanical quality factor Q was found to dramatically decrease, because the domain wall motion and friction between vibrator and pressure-transmitting fluid were enhanced under hydrostatic pressure. On the other hand, the pressure induced depolarization and phase transition were not observed in the experimental pressure range.

The influence of the hydrostatic pressure on the piezoelectric response for tetragonal BaTiO3 and PbTiO3 monodomain crystals is investigated using Landau–Ginzburg–Devonshire phenomenological approach. It is shown that hydrostatic pressure could enhance the piezoelectric properties in some directions of crystals. The piezoelectricy enhancement is attributed to the hydrostatic pressure-induced flattening of the elastic Gibbs free-energy profile and its corresponding dielectric softening. For BaTiO3 at 285 K, with increasing pressure, the free-energy profile tends to become flat along the polar [001]c direction, facilitating the dilatation and contraction of polarization. So the dielectric softens and the d33 obviously increases in the [001]c direction. But in the direction perpendicular to the polarization, the free-energy profile goes to steepen, which restrains the polarization rotation away from the [001]c polar axis and in turn makes the shear piezoelectric coefficient d15 decreased. As a result, the ma...