S. G. Lu

Tunability and relaxor properties of ferroelectric barium stannate titanate ceramics

Barium stannate titanate [Ba(SnxTi1−x)O3, x=0.1, 0.2, 0.3, and 0.4] ceramics were prepared using a conventional solid-state reaction process. Their dielectric properties were measured under direct current bias fields ranging from 0to2.5kV∕cm. A transformation from normal to relaxor ferroelectrics was observed when x⩾0.3. Broken long-range order or “dirty” ferroelectric domains and nanodomains were observed in Ba(Sn0.1Ti0.9)O3 and Ba(Sn0.4Ti0.6)O3 by transmission electron microscopy, respectively. Voltage driven tunability was found to decrease with increasing Sn content. The change from normal ferroelectric into relaxor ferroelectric had a negative impact on the tunability value of the materials.

Enhanced magnetoelectric effect in Terfenol-D and flextensional cymbal laminates

A magnetoelectric (ME) laminate configuration was fabricated using a flextensional cymbal located between two magnetostrictive Terfenol-D (Tb1−xDyxFe2) plates. The laminate, operating in transverse magnetized/transverse polarized mode, has a ME voltage coefficient of 56.8mV∕Oe under a magnetic bias field of 1kOe, which is larger than that of conventional Terfenol-D/PZT/Terfenol-D configuration. It is believed that the enhancement of ME effect is due to the coupling between the magnetostriction of Terfenol-D and the high piezoelectric response of cymbal.

Temperature driven nano-domain evolution in lead-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics

Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

Tunability and permittivity-temperature characteristics of highly (100) oriented compositionally graded (Ba0.7Sr0.3)(SnxTi1−x)O3 thin films grown by pulse-laser deposition

Compositionally graded (Ba0.7Sr0.3)(SnxTi1−x)O3 (BSSnT) (x=0.1, 0.2, 0.3, and 0.4) thin films were prepared by pulse-laser deposition on (La0.7Sr0.3)CoO3∕LaAlO3 substrates. A highly (100) oriented structure was obtained for both the upgraded (x increased from the bottom layer) and downgraded (x decreased from the bottom layer) configurations. The tunabilities are 31% and 35% for up- and downgraded BSSnT thin films at 300kV∕cm, respectively. Both the up- and downgraded BSSnT thin films exhibit near linear permittivity-temperature characteristics in the temperature range of −150to150°C. Fine grain size and graded configuration are believed to be responsible for this dielectric behavior.

Effect of dc bias on the Curie–Weiss exponent in 0.76Pb(Mg1∕3Nb2∕3)O3–0.24PbTiO3 ferroelectric single crystal

Permittivity versus temperature characteristics and Curie–Weiss exponent (CWE) γ in the universal Curie–Weiss law [e−1=em−1[1+(T−Tc)γ∕(2δ2)](1⩽γ⩽2)] as a function of dc bias field were obtained for ⟨001⟩, ⟨011⟩, and ⟨111⟩ oriented 0.76Pb(Mg1∕3Nb2∕3)O3–0.24PbTiO3 single crystals. Results indicated that γ is a function of dc bias field and three different oriented crystals show slight different γ values but the similar dc field dependence.