Switching domains

Dynamic domain imaging or Kerr microscopy of low coercivity thin films at MHz domain-switching frequencies allows one to examine domain wall motion in detail. ... 

Ferroelectric Domain Switching is recognized, different from that in micro-nano type ceramic composites. 

Analogous C(V) curves were recorded on pzt bulk ceramics with compositions around the morphotropic phase boundary (mpb). Figure 1.25 displays the relative permittivity as a function of DC-bias for a tetragonal (x = 0.48), a morphotropic (x = 0.52) and a rhombohedral (.x = 0.58) sample. In contrast to thin films additional humps observed in the e E) curves. This could be explained by different coercive fields for 180° and non-180° domains [31]. Their absence in ferroelectric thin films could be taken as evidence for suppressed non-180° domain switching in thin films [30],... 

Two types of contributions to dielectric and piezoelectric properties of ferroelectric ceramics are usually distinguished [6], [9-12], One type is called an intrinsic contribution, and it is due to the distortion of the crystal lattice under an applied electric field or a mechanical stress. The second type is called an extrinsic contribution, and it results from the motion of domain walls or domain switching [8], To provide an understanding of material properties of pzt, several methods to separate the intrinsic and extrinsic contributions were proposed. These methods are indirect, and are based on measurements of the dielectric and piezoelectric properties of ferroelectric ceramics [8], [10-12], In the experiments reported in this paper a different approach is adopted, which is based on measurements of high-resolution synchrotron X-ray powder diffraction. The shift in the positions of the diffraction peaks under applied electric field gives the intrinsic lattice deformation, whereas the domain switching can be calculated from the change in peak intensities [13,14],... 

Non-180° domain switching in rhombohedral pzt is characterized by a change of the ratio of the peak intensity within the (lll)/(—111) reflex group, Figure 7.10. At E = 0,... 

In this paper we present a comprehensive experimental and theoretical description of nanodomain reversal in fe bulk crystals an experimental method for domain switching using hvafm, results on nanodomain switching using hvafm and under indirect electron beam exposure, theory of fe domain breakdown and our last development of the fabrication of nanodomain gratings by the use of multiple tip arrays. We show that fdb is a new physical phenomenon observed in bulk fe crystals, and is the basis for the development of nanodomain technology in bulk fe crystals. This technology is required for future photonic, acoustic and microelectronic devices. 

Fig. 2.44 Schematic illustrating the changes accompanying the application of electrical and mechanical stresses to a polycrystalline ferroelectric ceramic (a) stress-free - each grain is non-polar because of the cancellation of both 180° and 90° domains (b) with applied electric field - 180° domains switch producing net overall polarity but no dimensional change (c) with increase in electric field 90° domains switch accompanied by small ( 1%) elongation (d) domains disorientated by application of mechanical stress. (Note the blank grains in (a) and (b) would contain similar domain structures.)...

When a critical field (Ec) is reached, which is near to the coercive field, the domains switch direction as a whole involving considerable hysteresis loss. This loss is proportional to the area of the loop, so that for the single crystal in Fig 2.46(a) it amounts to about 0.1 MJm-3. At 100Hz the power dissipated as heat would be 100 MW m-3, which would result in a very rapid rise in temperature. The dissipation factor (tan (5) is also very high at high field strengths, but becomes small at low field strengths, as described above. Modifications to the composition diminish the loss still further. 

Since the polar axes in barium titanate and PZT (see Fig. 2.40(b) and Fig. 2.44) are longer than the perpendicular axes, ceramics expand in the polar direction during poling. The application of a high compressive stress in the polar direction to a poled ceramic causes depoling since the 90° domains switch direction as a result of the ferroelastic effect and the polar directions of the crystallites become randomized. 

When the electric field is higher than the coercitive field strength, the spontaneous polarisation is switched and the dipoles reorientate along the field lines. This process of domain switching for Eei=Ec can be described in three steps i) nucleation of an anti-parallel domain, ii) domain growth and iii) saturation of the polarisation [461, 462]. 

As mentioned above, domain switching in ferroelectrics is accompanied by domain nucleation, moving domain walls and restructuring of dipoles and charges. A characteristic feature of this irreversible process is the appearance of a hysteresis loop in the dependence of dielectric displacement... 

Figure 6.26 The flexoelectric effect in BaTiO (a) the evolution of the potential energy curve under a homogeneous stress and in a strain gradient (b) domain switching via mechanical stress imposed by a probe (Original data from Lu et al. (2012))...

Jones, J., Motahari, S.M., Varlioglu, M Lienert, U., Bernier, J.V., Hoffman, M and Ustiindag, E. (2007) Crack tip process zone domain switching in a soft lead zirconate titanate ceramic. Acta Mater., 55, 5538-5548. 

Zhang, L.X. and Ren, X. (2005) In situ observation of reversible domain switching in aged Mn-doped BaTi03 single crystals. Phys. Rev., B71, 174108. 

Ren, X. (2004) Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching. Nat. Mater., 3, 91—94. 

Jones, J.L, Hoffinan, M., and Bowman, KJ. (2005) Saturated domain switching textures and strains in ferroelastic ceramics./. Appl. Phys., 98 (2), 024115. 

Fang, F, Yang, W., and Zhu, T, (1999) Crack tip 90° domain switching in tetragonal lanthanum-modified lead zirconate titanate under an electric field. J. Mater. Res., 14, 2940-2944. 

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