Flexoelectricity can play an important role in the reversal of the self‐polarization direction in epitaxial BiFeO3 thin films. The flexoelectric and interfacial effects compete with each other to ...determine the self‐polarization state. In Region I, the self‐polarization is downward because the interfacial effect is more dominant than the flexoelectric effect. In Region II, the self‐polarization is upward, because the flexoelectric effect becomes more dominant than the interfacial effect.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Flexoelectric control of defect formation and associated electronic function is demonstrated in ferroelectric BiFeO3 thin films. An intriguing, so far never demonstrated, effect of internal electric ...field (Eint) on defect formation is explored by a means of flexoelectricity. Our study provides novel insight into defect engineering, as well as allows a pathway to design defect configuration and associated electronic function.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The structure of lead-free (1-x)(Bi0.5Na0.5)TiO3-xSrTiO3 (BNT-STx) ceramics was analyzed by the Rietveld method, using X-ray diffraction and neutron scattering data. The structural refinement results ...suggest that the crystal structure successively changes with SrTiO3 concentration, x, from the rhombohedral phase (x=0.00) to rhombohedral and tetragonal (x=0.10–0.30), tetragonal and cubic (x=0.40–0.60), and finally cubic (x=0.80–1.00) phases. Correlation between the charge sensor constant (d33) and the weighted off-center value (dw) was observed, which may be attributed to the increased dipole motion in the unit cell due to an increased tendency to respond to external stimulation. Furthermore, an improved charge sensor constant (d33) of 140 pC/N was observed for BNT-ST0.20, and a large strain of 0.25% and a d33* value of 443 pm/V were observed from x=0.30.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Three different series of lead-free ceramics, i.e., (1-y)Bi1.03(1-x)LaxFeO3–yBaTiO3 (y = 0.27, x = 0.00–0.12), (y = 0.30, x = 0.00–0.10), and (y = 0.33, x = 0.00–0.08) are prepared via a conventional ...solid-state reaction with water quenching. From X-ray diffraction and electrical property measurements, two morphotropic phase boundaries (MPBs) are discovered in all three ceramic systems. The first MPB (MPB-I) appeared between rhombohedral and tetragonal phases, whereas the second MPB (MPB-II) appeared between tetragonal and cubic-like phases. The highest direct piezoelectric coefficients (d33 = 201, 274, and 268 pC/N) are mainly attributed to the typical MPB-I of the rhombohedral and tetragonal phases. However, the highest converse piezoelectric coefficients (d33∗ = 490, 500, and 570 pm/V with Curie temperature > 330 °C) are obtained for compositions near to the MPB-II. A significant enhancement in the dielectric constant at low temperature is associated with the local structural heterogeneity by La3+ doping, which serves as an origin for a high piezoelectric strain response. Based on the crystal structure as well as on the dielectric, ferroelectric, and piezoelectric properties, a phase diagram is constructed for La-doped BiFeO3BaTiO3 ceramics. This phase diagram reveals the relationship between piezoelectric performance and crystal structure.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present work, composition dependent crystal structure, ferroelectric, piezoelectric, and temperature dependent dielectric properties of the BiGaO
3
-modified (1–
x
)(0.65Bi
1.05
FeO
3
...–0.35BaTiO
3
) (BFBT35–
x
BG, where
x
= 0.00–0.03) lead-free ceramics were systematically investigated by solid-state reaction method, followed by water quenching process. The substitution of BG successfully diffuses into the lattice of the BFBT ceramics, without changing the pseudo-cubic structure of the samples. The scanning electron microscopy (SEM) results revealed that the average grain size was increased with BG-content in BFBT system. The BFBT–
x
BG ceramics showed a maximum in permittivity (ɛ
max
) at temperatures (
T
max
) above 500 °C in the compositional range of 0.00 ≤
x
≤ 0.03. The electro-strain is measured to be 0.125% (
d
*
33
~ 250 pm/V) under unipolar fields (5 kV/mm) for BFBT–0.01BG ceramics. The same composition (
x
= 0.01), large static piezoelectric constant (
d
33
~ 165 pC/N) and electromechanical coupling factor (
k
p
~ 25%) were obtained. The above investigated characterizations suggests that BFBT–BG material is favorable for piezoelectric and high temperature applications.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Different manganese oxides-doping effects were compared in piezoceramic BiFeO3-BaTiO3 system. 0.67Bi1.05(Fe0.99Mnx0.01)O3-0.33BaTiO3 (valence state x = 4+, 3+, and 2+) ceramics were prepared via a ...solid-state reaction process followed by furnace-cooling (FC) or water-quenching (WQ) process. For the FC ceramics, the direct piezoelectric sensor coefficient (d33) was almost independent of valence state of doped Mn, while d33 depended on the fraction of Fe3+/Fe2+ in WQ ceramics. The d33 value was highest for the donor Mn4+-doped ceramic, among the FC ceramics, with 175 pC/N. However, acceptor-doping with Mn2+ prevented the transition of Fe ion valence state from 3+ to 2+ in the WQ ceramics, the Mn2+-doped WQ ceramic showed the largest d33 of 313 pC/N and converse piezoelectric actuator coefficient, d33* of 352 pm/V, with high Curie phase transition temperature (482 °C).
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Three types of green compacts were formed by using applied loads of 1, 2, and 3 ton, respectively, and were sintered at 980 ◦C. The sintered ceramics with an applied load of 1 ton had the highest ...volume shrinkage, but the density was almost similar for all ceramics. There was no change in the crystal structure for all ceramics. The piezoelectric and the ferroelectric properties of the ceramics showed that the ceramic with an applied load of 1 ton had the best direct piezoelectric coefficient (
d
33
) and the largest remnant polarization. The microstructure indicated that the ceramics with an applied load of 1 ton had an average grain size of 6
μ
m. The results suggest that the piezoelectric property could be directly related to the grain size.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Temperature-insensitive high piezoelectric strain and low strain hysteresis (Hs) with high Curie temperature (TC) are desirable for piezoelectric actuator applications. The excellent room-temperature ...piezoelectric performance (d33 = 309 pC/N and d33∗ = 458 pm/V) with very high TC = 482 °C have achieved in 0.67Bi1.03FeO3-0.33Ba1-xLaxTiO3 ceramics. Furthermore, a small variation in the piezoelectric strain (ΔST = 13%) in the temperature range of 25 °C–125 °C with low strain hysteresis (Hs = 12%) and a large average electrostrictive coefficient (Q33 = 0.03 m2/C4) leads to a high figure of merit for piezoelectric actuators. The structural origin of the high piezoelectric performance is related to the crystal structure morphotropic phase boundary and maximum crystal structure lattice distortion (90° ̶ αR = 0.12° and cT/aT = 1.008). While the physical origin is mainly attributed to the soft ferroelectric effect by La3+ as donor doping on Ba2+-site that significantly reduces the coercive field and makes it easy to switch ferroelectric polarization under the applied electric field. We believe that this breakthrough in lead-free ceramics opens a new development window for temperature-insensitive piezoelectric properties for the high-temperature commercial applications.
Display omitted
•Maximum d33 = 309 pC/N and d33∗ = 458 pm/V obtained with high TC = 482 °C.•Low strain hysteresis (12%) and small variation (13%) in strain leads to the high FOM.•Large average Q33 = 0.03 m2/C4 comparable to the other electrostrictive material.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Hard piezoelectric properties are investigated in lead‐free BiFeO
3
–BaTiO
3
(BF–BT) ceramics. Rhombohedral (R) phase ceramics of (1 –
x
)BF–
x
BT (
x
= 0.20–0.30) were prepared using a ...conventional solid‐state reaction and water‐quenching process. The R structure is observed in
x
= 0.20–0.275, and the R and tetragonal phases coexist at
x
= 0.30. The piezoelectric charge sensor coefficient (
d
33
) and electromechanical planar coupling factor (
k
p
) increase with increasing BT content, whereas the mechanical quality factor (
Q
m
) decreases. The
x
= 0.20 ceramic shows the best hard piezoelectric properties: the highest
Q
m
= 403 and the highest
T
C
= 607°C. In contrast,
x
= 0.30 ceramic shows soft piezoelectric properties:
d
33
= 301 pC/N and
k
p
= 0.33 with
T
C
= 510°C. These results show that the BF–BT system in R‐phase‐rich region has good hard piezoelectric properties for transducer applications.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
PDF
