This study investigates the variation of magnetoelectric (ME) coefficient as a function of the piezoelectric grain size in the composite system of 0.8 Pb(Zr0.52Ti0.48)O3–0.2 Ni0.8Zn0.2Fe2O4. It was found that as the piezoelectric-phase grain size increases the overall resistivity, piezoelectric, dielectric, and ferroelectric property of the composite increases and saturates above 600 nm. Below 200 nm average grain size, piezoelectric and dielectric properties decrease rapidly. The ferroelectric Curie temperature was found to decrease from 377 to 356 °C as the average grain size decreases from 830 to 111 nm. ME coefficient of the composite showed a rapid change below grain size of 200 nm and was found to saturate above 600 nm to a value of 155 mV/cm.Oe.

Effect of piezoelectric grain size on magnetoelectric coefficient of Pb(Zr0.52Ti0.48)O3–Ni0.8Zn0.2Fe2O4 particulate composites

BaTiO3 nanocrystal-mediated micro pseudo-electrochemical cells with ultrasound-driven piezotronic enhancement for polymerization

Dielectric, ferroelectric, and piezoelectric properties in potassium sodium niobate ceramics with rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries

The primary aims of this review article are (a) to develop the fundamental understanding of ME behavior in perovskite piezoelectric-spinel magnetostrictive composite systems, (b) to identify the role of composition, microstructural variables, phase transformations, composite geometry, and postsintering heat treatment on ME coefficient, and (c) to synthesize, characterize, and utilize the high ME coefficient composite. The desired range of ME coefficient in the sintered composite is 0.5–1 V/cm⋅Oe. The studies showed that the soft piezoelectric phase quantified by smaller elastic modulus, large grain size of piezoelectric phase (~1 μm), and layered structures yields higher magnitude of ME coefficient. It is also found that postsintering thermal treatment such as annealing and aging alters the magnitude of magnetization providing an increase in the magnitude of ME coefficient. A trilayer composite was synthesized using pressure-assisted sintering with soft phase [0.9 PZT–0.1 PZN] having grain size larger than 1 μm and soft ferromagnetic phase of composition Ni0.8Cu0.2Zn0.2Fe2O4 [NCZF]. The composite showed a high ME coefficient of 412 and 494 mV/cm⋅Oe after sintering and annealing, respectively. Optimized ferrite to PZT thickness ratio was found to be 5.33, providing ME coefficient of 525 mV/cm⋅Oe. The ME coefficient exhibited orientation dependence with respect to applied magnetic field. Multilayering the PZT layer increased the magnitude of ME coefficient to 782 mV/cm⋅Oe. Piezoelectric grain texturing and nanoparticulate assembly techniques were incorporated with the layered geometry. It was found that with moderate texturing, d33 and ME coefficient reached up to 325 pC/N and 878 mV/cm⋅Oe, respectively. Nanoparticulate core shell assembly shows the promise for achieving large ME coefficient in the sintered composites. A systematic relationship between composition, microstructure, geometry, and properties is presented which will lead to development of high-performance magnetoelectric materials.

Progress in Dual (Piezoelectric-Magnetostrictive) Phase Magnetoelectric Sintered Composites

Density functional theory at the level of the local density approximation with the projector augmented wave method is used to determine the structure of 180° domain walls in tetragonal ferroelectric PbTiO3. In agreement with previous studies, it is found that PbO-centered {100} walls have lower energies than TiO2-centered {100} walls, leading to a Peierls potential barrier for wall motion along 010 of ~ 36 mJ m − 2. In addition to the Ising-like polarization along the tetragonal axis, it is found that near the domain wall, there is a small polarization in the wall-normal direction away from the domain wall. These Neel-like contributions to the domain wall are analyzed in terms of the Landau–Ginzburg–Devonshire phenomenological theory for ferroelectrics. Similar characteristics are found for {110} domain walls, where OO-centered walls are energetically more favorable than the PbTiO-centered walls.

https://iopscience.iop.org/article/10.1088/0953-8984/23/17/175902/pdf

Structure and energetics of 180° domain walls in PbTiO3 by density functional theory.

The effect of grain size on domain structure in unsupported thin films with grains (70 - 250 nm) was studied by using TEM. It is found that there probably exists a critical grain size near 200 nm, at which an abrupt change in domain structure occurs. Above this size, domains, which are lamellar microtwins, appear in almost all of the coarse grains. The domain width decreases with grain size. Below this size, however, most of the grains are single-domain ones, while some irregular and curved domain walls appear only in a small portion of the fine grains. The number of the single-domain grains increases with decreasing grain size. Such a grain-size dependence of domain structure is correlated with the anomalous behaviours of the coercive field and dielectric constant in ferroelectric thin films. This interesting result has not been reported before.

C J Lu

Papers

The effect of grain size on domain structure in unsupported thin films