Planar Electromechanical Coupling Kp Research Articles

Enhanced Electromechanical Performance in Lead-free (Na,K)NbO3-Based Piezoceramics via the Synergistic Design of Texture Engineering and Sm-Modification.

Next-generation electromechanical conversion devices have a significant demand for high-performance lead-free piezoelectric materials to meet environmentally friendly requirements. However, the low electromechanical properties of lead-free piezoceramics limit their application in high-end transducer applications. In this work, a 0.96K0.48Na0.52Nb0.96Sb0.04O3-0.04(Bi0.5-xSmx)Na0.5ZrO3 (abbreviated as T-NKN-xSm) ceramic was designed through phase regulation and texture engineering, which is expected to solve this difficulty. Through our research, we successfully demonstrated the enhanced electromechanical performance of lead-free textured ceramics with a highly oriented [001]c orientation. Notably, the T-NKN-xSm textured ceramics doped with 0.05 mol % Sm exhibited the optimal electromechanical performance: piezoelectric coefficient d33 ≈ 710 pC N-1, longitudinal electromechanical coupling k33 ≈ 0.88, planar electromechanical coupling kp ≈ 0.80, and Curie temperature Tc ≈ 244 °C. Finally, we conducted a detailed investigation into the phase and domain structures of the T-NKN-Sm ceramics, providing valuable insights for achieving high electromechanical properties in NKN-based ceramics. This research serves as a crucial reference for the development of advanced electromechanical devices by facilitating the utilization of lead-free piezoelectric materials with superior performance and environmental benefits.

Study on structure and properties of Pb(Sc1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary ceramics near morphotropic phase boundary

xPb(Sc1/2Nb1/2)O3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 (xPSN–yPMN–zPT, x/y/z=5/61/34, 25/38/37, 45/14/41) ceramics with morphotropic phase boundary (MPB) were prepared by a modified two-step columbite precursor method. The structure and electrical properties of ceramics were investigated. X-ray diffraction shows a pure perovskite structure without any trace of second phase. All of the ceramics exhibit high density and homogeneous microstructure, indicating that the modified two-step columbite precursor method is very feasible to fabricate PSN–PMN–PT ceramics. With increasing the content of PSN, the Curie temperature TC and phase transition temperature of rhombohedral to tetragonal TR–T increased obviously. The optimal properties achieved in 25PSN–38PMN–37PT with piezoelectric coefficient d33=478pC/N, dielectric permittivity εmax=8338, planar electromechanical coupling kp=65.1%, and Curie temperature TC=192.2°C, respectively. Dielectric measurement shows that the PSN–PMN–PT ceramics near MPB display the relaxor-like characteristics.

Effects of Nb,Mn doping on the Structure, Piezoelectric, and Dielectric Properties of 0.8Pb(Sn0.46Ti0.54)O3–0.2Pb(Mg1/3Nb2/3)O3 Piezoelectric Ceramics

Nb and Mn were doped, respectively, to 0.8Pb(Sn0.46Ti0.54)O3–0.2Pb(Mg1/3Nb2/3)O3 (PST–PMN) to improve electrical properties for meeting the requirement in various fields. The additions of Nb and Mn influence in a pronounced way the structure, and improve the densities of the ceramics. Nb‐doped PST–PMN increased the piezoelectric coefficient d33, planar electromechanical coupling kp, and relative dielectric constant ε, indicating “soft” piezoelectric behavior. Mn doping played a “hard” part, which significantly enhanced the mechanical quality factor Qm without deteriorating other piezoelectric properties. The most excellent properties of Nb‐doped PST–PMN were obtained with doping amount of 0.75 mol%, specifically d33, kp, being on the order of 455 pC/N, 57.5% and 3560, respectively. The addition of 0.75 mol% Mn for PST–PMN presented the optimum electrical properties, with Qm of 554, d33 of 430 pC/N, kp of 57.0%, ε of 2770. It was proposed that the addition of Nb, Mn generated different defect dipoles involved in the domain walls motion and intrinsic piezoelectric responses, leading to different effects on electrical properties.

Piezoelectric Property and Strain Behavior ofPb(Yb0.5Nb0.5)O3–PbHfO3–PbTiO3Polycrystalline Ceramics

(1−x)Pb(Hf1−yTiy)O3–xPb(Yb0.5Nb0.5)O3(x = 0.10–0.44,y = 0.55–0.80) ceramics were fabricated. The morphotropic phase boundary (MPB) of the ternary system was determined byX‐ray powder diffraction. The optimum dielectric and piezoelectric properties were achieved in 0.8Pb(Hf0.4Ti0.6)O3–0.2Pb(Yb0.5Nb0.5)O3ceramics withMPBcomposition, where the dielectric permittivity εr, piezoelectric coefficientd33, planar electromechanical couplingkp, and Curie temperatureTcwere found to be on the order of 1930,480 pC/N, 62%, and 360°C, respectively. The unipolar strain behavior was evaluated as a function of applied electric field up to 50 kV/cm to investigate the strain nonlinearity and domain wall motion under large drive field, where the high field piezoelectricd33* was found to be 620 pm/V for 0.82Pb(Hf0.4Ti0.6)O3–0.18Pb(Yb0.5Nb0.5)O3. In addition, Rayleigh analysis was carried out to study the extrinsic contribution, where the value was found to be in the range 2%–18%.

Dielectric, piezoelectric, and ferroelectric properties of Al2 O3 and MnO2 modified PbSnO3 -PbTiO3 -Pb(Mg1/3 Nb2/3 )O3 ternary ceramics

The PbSnO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 (PST–PMN) ternary system with morphotropic phase-boundary (MPB) compositions were fabricated using a two-step columbite precursor method. The effects of Al2O3 and MnO2 addition on the dielectric, piezoelectric, and ferroelectric properties of PST–PMN were investigated. MnO2 acted as an acceptor dopant and induced a “hardening” effect in PST–PMN, with decreased piezoelectric coefficients d33 and increased mechanical quality factors Qm, while the addition of Al2O3 led to the significant decrease of piezoelectric properties, attributed to the second phase. Of particular interest is the fact that the Mn-doped PST–PMN exhibited excellent properties when the doping level was in the range of 0.2–0.5 wt%, with piezoelectric d33, planar electromechanical coupling kp, dielectric permittivity ϵr, Qm, remnant polarization Pr and coercive field EC being on the order of ∼510 pC N−1, ∼57%, 3120–3500, 530–600, 27–30 µC cm−2, and ∼8 kV cm−1, respectively, showing advantages over commercial PZT4-type ceramics, which are promising for high-power electromechanical applications.

Dielectric and piezoelectric properties of manganese‐modified PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics with morphotropic phase boundary compositions

AbstractHigh piezoelectric and electromechanical properties were reported in the PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary system with morphotropic phase boundary (MPB) compositions. This work focuses on the effect of MnO2 addition on 0.8Pb(Hf0.443Ti0.557)O3–0.2PMN (0.8PHT–0.2PMN) ceramics. It was observed that the Mn acceptor modification induced a “hardening” effect in 0.8PHT–0.2PMN, with decreased piezoelectric coefficients d33 and dielectric loss tan δ and a significantly increased mechanical quality factor Qm. Moreover, the 0.2 wt% MnO2‐doped 0.8PHT–0.2PMN ceramics exhibited good piezoelectric and electromechanical properties with d33, planar electromechanical coupling kp and Qm being on the order of 360 pC/N, 61% and 700, respectively, showing advantages compared to those of commercial hard PZT4 ceramics, which is attractive for high power applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of ZnO nanoneedles addition on the mechanical and piezoelectric properties of hard PZT-based composites

Hard PZT (PZT4)-based composites embedded by ZnO nanoneedles (denoted as PZT/ZnOn) were fabricated by a solid state sintering technique. The characteristic diffraction peaks of the perovskite PZT and ZnO phases were identified from the studied composites, indicating the retention of ZnOn. With increasing ZnOn content, the grain size of the composites was reduced gradually. In contrast with the pure PZT, the PZT/ZnOn composites possessed more excellent mechanical properties, while the piezoelectric properties were reduced by a certain extent. The best mechanical properties of PZT/ZnOn composites were obtained by sintering at 1,150 °C with 1.5 wt% ZnO nanoneedles addition: fracture toughness K IC ~ 2.04 MPa m1/2, flexural strength σ f ~ 105.44 MPa, compressive strength σ c ~ 543.89 MPa. The piezoelectric properties of the PZT/ZnOn composites were found to be lower than that of the pure PZT with dielectric permittivity e r of 768–893, piezoelectric coefficient d 33 of 240–260pC/N, mechanical quality factor Q m of 340–650 and planar electromechanical coupling k p of 0.5–0.55.

Piezoelectric properties of PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics

Abstract(1 – x)Pb(Hf1–yTiy)O3–x Pb(Mg1/3Nb2/3)O3 (x = 0.1 ∼ 0.25, y = 0.555) ternary piezoelectric ceramics were prepared using the two‐step precursor method. Morphotropic phase boundary (MPB) compositions, located at x = 0.18 ∼ 0.22, were confirmed using X‐ray diffraction and by their dielectric, piezoelectric and ferroelectric properties. The optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.8Pb(Hf0.445Ti0.555)O3–0.2Pb(Mg1/3Nb2/3)O3, with dielectric permittivity εr, piezoelectric coefficient d33, planar electromechanical coupling kp and Curie temperature TC being on the order of 2800, 680 pC/N, 70% and 276 °C, respectively. Of particular significance is that the new ternary ceramics exhibit comparable piezoelectric and electromechanical properties to commercial PZT5H ceramics, but with much improved TC, showing a potential for applications at elevated temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of sintering temperature on microstructure and electric properties of CuO doped alkaline niobate-based lead-free ceramics

In this work, microstructure characteristics, dielectric, piezoelectric and ferroelectric properties of lead-free (K0.4425Na0.52Li0.0375)(Nb0.87Ta0.06Sb0.07)O3 (KNLNST) doped with 1 mol% copper oxide (CuO) piezoelectric ceramics prepared by a conventional solid-state reaction route are investigated with an emphasis on the influence of sintering temperature. The introduction of CuO could significantly improve the sinterability of KNLNST ceramics. It is found that the tetragonality of the ceramics increases with raising sintering temperature. A dense microstructure with increased grains is developed, probably due to liquid-phase sintering. Both the piezoelectric constant d33 and planar electromechanical coupling kp increase with increasing relative density and grain size. The Curie temperature TC values increase slightly when the sintering temperature is increased. In addition, the KNLNST ceramics doped with 1 mol% CuO show obvious dielectric relaxor characteristics, and the relaxor behavior of ceramics is strengthened by increasing the sintering temperature. The improved piezoelectric and dielectric properties of d33 = 241 pC/N, kp = 0.437, dielectric loss tanδ = 0.0087, mechanical quality factor Qm = 138, dielectric constant er = 1,304 can be obtained for specimens sintered at 1,080 °C for 3 h.

Effects of Nb2O5 addition on the microstructure, electrical, and mechanical properties of PZT/ZnO nanowhisker piezoelectric composites

Nb2O5-modified PZT/ZnO nanowhisker (denoted as PZT/ZnOw–Nb2O5) piezoelectric composites were prepared by a solid state sintering technique. Effects of Nb2O5 addition on the microstructure, electrical, and mechanical properties of the PZT/ZnOw composites were investigated. With increasing Nb2O5 content, the grain size of the composites was reduced and the fracture mode changed from intergranular to intragranular gradually. Compared with the PZT/ZnOw composites, the dielectric, piezoelectric, and ferroelectric properties of the PZT/ZnOw–Nb2O5 composites were improved significantly, while mechanical properties were enhanced slightly. The optimum electrical and mechanical properties were achieved for the PZT/ZnOw composites modified with 0.75 wt% Nb2O5 sintered at 1150 °C, with dielectric permittivity er, piezoelectric coefficient d 33, planar electromechanical coupling k p, remnant polarization P r, fracture toughness K IC, and flexural strength σf being on the order of 4930, 600 pC/N, 0.63, 29.2 μC/cm2, 1.56 MPa m1/2 and 130 MPa, respectively. The Nb2O5-modified PZT/ZnOw piezoelectric composites, with comparable electrical properties and improved mechanical properties than those of commercial PZT-5H ceramics, are promising candidates for further applications.

Investigation of ternary system Pb(Sn,Ti)O3–Pb(Mg1/3Nb2/3)O3 with morphotropic phase boundary compositions

(1 − x)Pb(Sn1−yTiy)O3–xPb(Mg1/3Nb2/3)O3 (x = 0.1–0.4, y = 0.45–0.65) ternary system was prepared using two-step columbite precursor method. Phase structure of the synthesized ceramics was studied by using X-ray powder diffraction and the morphotropic phase boundary (MPB) curve of the ternary system was confirmed. The isothermal map of Curie temperature (TC) in the phase diagram was obtained based on the dielectric–temperature measurements. The coercive field EC and internal bias field Ei were found to increase with increasing PT content, while decrease with increasing PMN content. The optimum properties were achieved in the MPB composition 0.8Pb(Sn0.45Ti0.55)O3–0.2Pb(Mg1/3Nb2/3)O3, with dielectric permittivity ɛr, piezoelectric coefficient d33, planar electromechanical coupling kp, mechanical quality factor Qm and TC of being on the order of 3040, 530pC/N, 55.5%, 320 and 190 °C, respectively, exhibiting potential usage for high power application.

Piezoelectric Ceramics in the PbSnO3–Pb(Mg1/3Nb2/3)O3–PbTiO3 Ternary System

Piezoelectric ceramics in the ternary system (0.8−x)PbSnO3–0.2Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PSn–PMN–PT, x = 0.42–0.47) were synthesized. Morphotropic phase boundary (MPB) compositions, located at ~PT = 0.43–0.45 were confirmed by X‐ray diffraction, dielectric, piezoelectric, and ferroelectric properties. The coercive field EC, internal bias field Ei, and mechanical quality factor Qm were found to increase with increasing PT content, indicative of piezoelectric “hardening” characteristics, while the optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.36PSn–0.2PMN–0.44PT, with dielectric permittivity εr, piezoelectric coefficient d33, and planar electromechanical coupling kp being on the order of 2930, 510 pC/N and 55%, respectively. In addition, the aging behavior of the piezoelectric ceramics was studied, with aging rate of d33 ~−6%, kp ~−2%, εr ~−7% per decade, respectively, similar to commercial PZT4 ceramics.

Properties of Co-Doped 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO3 Lead-Free Ceramics

Lead-free piezoelectric ceramics0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3+xmol% Co3+(BNBT-Co, x = 0–8) are prepared by the solidstate reaction method. Effects of the amount of Co3+ on theelectrical properties and phase transition are studied. The resultsindicate that the addition of Co3+ enhances the mechanicalquality factor Qm significantly, whereas the dissipationfactor tan δ has a minimum value at x = 3.5. Meanwhile, addition ofCo3+ leads to small decreases of piezoelectric constant d33,and planar electromechanical coupling kp. The present0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3+3.5 mol%Co3+ ceramics exhibit good performance with mechanical qualityfactor Qm = 910, piezoelectric constant d33 = 106 pC/N, planarelectromechanical coupling kp = 10% and dissipation factortan δ = 1.1% at 1 kHz. Saturated polarization hysteresis loops havebeen obtained for BNBT-Co ceramics. Two dielectric peaks atdepolarization temperature Td and Tm appear in the curves ofεT33 vs temperature for the pure BNBT ceramics. However, thefirst dielectric peak Td disappears after the addition of Co3+,which means that the transition from ferroelectric to antiferroelectricphase has been eliminated.