Acoustic emission and dielectric studies of phase transitions within the morphotropic phase boundary of xPb(Zr1/2Ti1/2)O3-(1−x)Pb(Ni1/3Nb2/3)O3 relaxor ferroelectrics

We have carried out a combined acoustic emission(AE) and dielectricpermittivity study of the xPb(Zr1/2Ti1/2)O3-(1−x)Pb(Ni1/3Nb2/3)O3relaxor ferroelectric ceramics with compositions x=0.7–0.9 corresponding to its morphotropic phase boundary. Temperatures of all phase transitions occurring on heating are identified accurately by AE, and a direct transition between the low-temperature (rhombohedral) and high-temperature (pseudocubic) relaxor phases is found. The AE peak intensity is generally proportional to the temperature derivative of the dielectricpermittivity, in agreement with a model proposed for a thermally cycled small elastic dipole

Domain structure-dielectric property relationship in lead-free (1−x)(Bi1/2Na1/2)TiO3xBaTiO3 ceramics

The domain morphology and crystal structure of (1−x)(Bi1/2Na1/2)TiO3xBaTiO3 lead-free piezoelectric ceramics were systematically studied with transmission electron microscopy for compositions x=0.04through 0.11. It was found that the ceramics with compositions x\u3c0.06 display a R3csymmetry with ferroelectric domains of ∼100 nm forming complex structures at room temperature. Only nanodomains with faint contrast were observed in the compositions of 0.07≤x≤0.09. The presence of weak 1/2 (ooe)superlattice diffraction spots and absence of 1/2 (ooo) ones (o stands for odd and e stands for even miller indices) seem to suggest a P4bm symmetry at room temperature. The morphotropic phase boundary composition x=0.06 showed mixed R3c and P4bm phases. Large lamellar ferroelectric domains with P4mm symmetry were found to dominate in the ceramic of x=0.11. The observed domain structure correlates extremely well with the frequency dispersion of dielectric constant at room temperature and a new concept “relaxor antiferroelectric” was proposed to describe the dielectric behavior of compositions 0.07≤x≤0.09. These results are summarized in a phase diagram for unpoled ceramics in the (1−x)(Bi1/2Na1/2)TiO3xBaTiO3binary solid solution system

Characteristic temperatures and field effect in KTa

[100]-oriented KTa1−xNbxO3 (x=0.32) relaxor ferroelectric crystals have been studied by acoustic emission (AE) count rate $\dot{N}$ in the temperature range from 200 K to 700 K. Burns temperature Td=620 K ($\dot{N} = 1.7\,{\rm{s}}^{ - 1}$) and intermediate temperature T*=310 K ($\dot{N} = 3.1\,{\rm{s}}^{ - 1}$) as well as both the tetragonal-cubic TT-C=259 K ($\dot{N} = 4.0\,{\rm{s}}^{ - 1}$) and orthorhombic-tetragonal TO-T=243 K ($\dot{N} = 5.0\,{\rm{s}}^{ - 1}$) phase transition temperatures have been clearly detected. T* is found to be influenced by an external DC electric field E: T* essentially decreases with a slope of approximately − 60 K·cm/kV accompanied with weakening in $\dot{N}$, as E enhances. The mechanisms of abnormal T*(E) and $\dot{N}$(T) dependences are discussed

Acoustic emission study of domain wall motion and phase transition in (1-x-y)Bi0.5Na0.5TiO3-xBaTiO(3)-yK(0.5)Na(0.5)NbO(3) lead-free piezoceramics

The ferroelectric strain hysteresis and acoustic emissions of lead-free (1 - x - y)Bi0.5Na0.5TiO3-xBaTiO3-yK0.5Na0.5NbO3 ceramics were investigated at room temperature. The field-induced antiferroelectric ??? ferroelectric phase transition as well as the ferroelectric coercive field were successfully detected. Although the strain was largest for x = 0.06 and y = 0.02, this composition showed the lowest acoustic emission signals, making it an interesting material for ultrasonic transducer applications.close161

Acoustic emission during the ferroelectric transition Pm(3)over-barm to P4mm in BaTiO3 and the ferroelastic transition R(3)over-barm-C2/c in Pb-3(PO4)(2)

Acoustic emission (AE) spectroscopy without frequency filtering (∼broadband AE) and moderate time integration is shown to be sensitive enough to allow the investigation of subtle nano-structural changes in ferroelectric BaTiO3 and ferroelastic Pb 3(PO4)2. AE signals during weak phase transitions are compatible with avalanche statistics as observed previously in large-strain systems. While the data are too sparse to determine avalanche exponents, they are well suited to determine other thermodynamic parameters such as transition temperatures and critical stresses

Electric field dependence of characteristic temperatures in PbSc

Two model relaxor ferroelectrics PbSc0.5Ta0.5O3 (undergoing a spontaneous para-to-ferroelectric phase transformation) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (no long-range ferroelectric order in the absence of an external electric field) were studied by acoustic emission in the temperature range 200–600 K under a dc field E. Both compounds exhibit a para-to-antiferroelectric transformation at Tn, which is slightly above the temperature of the dielectric-permittivity maximum. For both compounds the intermediate temperature T* increases linearly with increasing E. The dT*/dE slope is larger than that of the ferroelectric transformation temperature Tc, similar to the transformation phenomena in BaTiO3. The T*(E) increase is suggested to be due to enhanced dipole polarizations inside the polar nanoregions

Detection of phase transitions in sodium bismuth titanate–barium titanate single crystals by acoustic emission

Acoustic emission measurements are combined with strain, dielectric, and polarization measurements to detect phase transitions in 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 single crystals during thermal cycling as well as electric field cycling at both room temperature and 140 °C. All phase transitions known from the literature (cubic↔tetragonal↔trigonal I↔trigonal II) are determined to be of first order, and the existence of the ferroelectric trigonal II phase at room temperature and its transformation into an antiferroelectric phase during heating above 130 °C is established