High Piezoelectric Properties Of D33 Research Articles

High piezoelectric performance and domain configurations of (K0.45Na0.55)0.98Li0.02Nb0.76Ta0.18Sb0.06O3 lead-free ceramics prepared by two-step sintering

Research for high-performance lead-free piezoelectric materials has become an urgent issue from the environmental concern. Very limited attempts on two-step sintering had been made so far. In this study, (K0.45Na0.55)0.98Li0.02Nb0.76Ta0.18Sb0.06O3 ceramics were prepared by both conventional sintering and two-step sintering. Piezoelectric properties, microstructure and domain structure were found to change significantly with sintering methods and sintering conditions. Two-step sintering was performed in the way that temperature is first quickly raised to 1180 °C, kept for 1 min, then immediately cooled down to 1120 °C and maintained for a desired time length. The effects of dwelling time on piezoelectric performance and microstructure as well as domain structure were investigated. High piezoelectric properties of d33 = 455 pC/N, kp = 0.54 and k33 = 0.67 were obtained in a ceramic prepared under the dwelling time of 20 h. This ceramic also possesses a very good piezoelectric thermal-ageing stability over −50 °C–150 °C. Further investigation reveals that this ceramic has a quite uniform grain-size distribution with the average grain size of about 12 μm in microstructure and shows domain patterns of simple parallel stripes with a hierarchical nanodomain structure appearing inside some of broad stripes. The observed excellent piezoelectric performance is considered to associate closely with the unique domain structure.

Multi-phase structure and electrical properties of Bi0.5Li0.5ZrO3 doping K0.48Na0.56NbO3 lead-free piezoelectric ceramics

(1–x)K0.48Na0.56NbO3–xBi0.5Li0.5ZrO3 (KNN–xBLZ, x = 0–0.06) lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method, and their phase structures and electric properties as well as TC were systematically investigated. The orthorhombic–tetragonal (O–T) two phases were detected in all (1–x)K0.48Na0.56NbO3–xBi0.5Li0.5ZrO3 ceramics at 0.01 ≤ x ≤ 0.05. Due to the appropriate ratio between O phase and T phase (CO/CT= 45/55), high piezoelectric properties of d33 = 239 pC/N, kp = 34%, and Pr = 25.23 μC/cm2 were obtained at x = 0.04. Moreover, a high TC = 348°C was also achieved in KNN–xBLZ ceramic at x = 0.04. These results indicate that (1–x)K0.48Na0.56NbO3–xBi0.5Li0.5ZrO3 system is a promising candidate for high-temperature piezoelectric devices.

Piezoelectric, ferroelectric and ferromagnetic properties of (1−x)BiFeO3–xBaTiO3 lead-free ceramics near morphotropic phase boundary

A series of solid solution of (1−x)BiFeO3–xBaTiO3 (abbreviated as BFO–xBT at 0.24 ≤ x ≤ 0.34) were prepared to reveal the relation between phase structure and multiferroic properties. A morphotropic phase boundary (MPB) separating R phase and T one was detected in BFO–xBT system at 0.26 ≤ x ≤ 0.34. Due to R and T two-phase coexistence, high piezoelectric properties of d 33 = 191 pC/N and k p = 34.68%, as well as excellent ferroelectric properties of 2P r = 56.13 μm/cm2 and 2E C = 75.35 kV/cm were achieved in the BFO–xBT ceramics at x = 0.30. Moreover, a low leakage current density (J) of 1.01 × 10−6–3.18 × 10−6 A/cm2 at an applied electric field of 30 kV/cm and a weak ferromagnetism with remanent magnetization M r of 0.014–0.054 emu/g and coercive fields H c of 946–2340 Oe were detected in BFO–xBT ceramics at 0.24 ≤ x ≤ 0.34, suggesting that the BFO–BT ceramics have promising prospects in magnetoelectric functional components.

Influence of Bi 4 Ti 3 O 12 doping on structural and piezoelectric properties of (K 0.4425 Na 0.52 Li 0.0375 )(Nb 0.87 Ta 0.06 Sb 0.07 )O 3 lead-free ceramics

Abstract Recently, (K, Na, Li)(Nb, Ta, Sb)O3 ceramics have attracted much attention of researchers, and have become one of the most popular systems of KNN-based ceramics. In this paper, Bi4Ti3O12 was added in the (K0.4425Na0.52Li0.0375)(Nb0.87Ta0.06Sb0.07)O3 ceramics (KNLNTS-x mol% BIT) to improve their piezoelectric properties. The phase formation and microstructure of KNLNTS-x mol% BIT ceramics were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). With the addition of BIT, the permittivity maxima of samples shifted toward higher temperature firstly and then shifted to lower temperature. All samples showed well ferroelectric behavior and the density of (1-x)KNLNTS-x mol% BIT ceramics were increased and reached a relative density of 99.4%. High piezoelectric properties of d33 = 255 pC/N, kp = 0.451, Qm = 186 were obtained for the samples containing 0.50 mol% BIT.

Structural and piezoelectric properties of barium-modified lead-free (K0.455Li0.045Na0.5)(Nb0.9Ta0.1)O3 ceramics

Ferroelectric (K0.455Li0.045Na0.5)(Nb0.9Ta0.1)O3 + x mol% BaCO3 ceramic compositions with Ba2+ as an A-site dopant in the range of x = 0–1.2 mol% were synthesized by conventional ceramic processing route. Effect of Ba2+ content on the microstructure, ferroelectric, dielectric, and piezoelectric properties of the ceramics was investigated. The results of X-ray diffraction reveal that Ba2+ diffuse into the (K0.455Li0.045Na0.5)(Nb0.9Ta0.1)O3 lattices to form a solid solution with a perovskite structure having typical orthorhombic symmetry. As Ba2+ content increases, cell volume and tetragonality increase in the crystal structure of the ceramics. Increasing doping level of Ba2+ inhibits grain growth in the ceramics and reduces both the Curie temperature (Tc) and tetragonal–orthorhombic phase transition temperature (To-t). The bulk density, remnant polarization Pr, room-temperature dielectric constant (e′RT), planar electromechanical coupling factor kp, and piezoelectric charge coefficient d33 are found to increase as Ba2+ concentration increases from 0 to 0.8 mol% and then decrease as Ba2+ content increases further from 0.8 to 1.2 mol%. High piezoelectric properties of d33 = 187 pC/N and kp = 48 % are found in 0.8 mol% Ba2+ composition. Optimum amount of Ba2+ dopant takes the polymorphic phase boundary region consisting of orthorhombic and tetragonal crystal structures of the ceramic system near the room temperature and enhances its piezoelectric properties.

High piezoelectric properties and good temperature stabilities of CuO-modified Ba(Ti0.96SnxZr0.04-x)O3 ceramics

In order to obtain both high piezoelectric property and good temperature stability in BaTiO 3-based ceramics in the common usage temperature range, Sn 4+ and Zr 4+ are co-doped into BaTiO 3 ceramics according to the formula of Ba ( Ti 0.96 Sn x Zr 0.04-x) O 3 (BTSZ) (x = 0.01–0.4) with 1 mol% CuO being added as sintering-aid in this study. The CuO -modified BTSZ ceramics show both high piezoelectric properties and good temperature stability. Particularly, the CuO -modified Ba ( Ti 0.96 Sn 0.01 Zr 0.03) O 3 ceramic displays the high piezoelectric properties of d33 = 350 pC/N, k p = 49.5% at room-temperature and a weak temperature dependence of kp in the temperature range of -15°C and 60°C. Moreover, the CuO -modified Ba ( Ti 0.96 Sn 0.01 Zr 0.03) O 3 ceramic shows stable thermal aging behavior with the d33 being almost unchanged until the aging temperature of 100°C, which is even higher than its Curie temperature. The high piezoelectric properties of CuO -modified Ba ( Ti 0.96 Sn 0.01 Zr 0.03) O 3 ceramic were ascribed to the dense microstructure with small and uniform grain size distribution. The stable thermal aging behavior can be explained by the aging effect based on the defect dipolar model.

Electrical properties of lead-free 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.52Ti0.48)O3 piezoelectric ceramics by optimizing sintering temperature

Lead-free 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.52Ti0.48)O3 [0.98NKN-0.02BZT] ceramics were fabricated by the conventional mixed oxide method with sintering temperature at 1,080°C to 1,120°C. The results indicate that the sintering temperature obviously influences the structural and electrical properties of the sample. For the 0.98NKN-0.02BZT ceramics sintered at 1,080°C to 1,120°C, the bulk density increased with increasing sintering temperature and showed a maximum value at a sintering temperature of 1,090°C. The dielectric constant, piezoelectric constant [d33], electromechanical coupling coefficient [kp], and remnant polarization [Pr] increased with increasing sintering temperature, which might be related to the increase in the relative density. However, the samples would be deteriorated when they are sintered above the optimum temperature. High piezoelectric properties of d33 = 217 pC/N, kp = 41%, dielectric constant = 1,951, and ferroelectric properties of Pr = 10.3 μC/cm2 were obtained for the 0.98NKN-0.02BZT ceramics sintered at 1,090°C for 4 h.

Low‐Temperature Sintering and Piezoelectric Properties of 0.65Pb(Zr1−xTix)O3–0.35Pb(Ni0.33Nb0.67)O3 Ceramics

0.65Pb(Zr1−xTix)O3–0.35Pb(Ni0.33Nb0.67)O3 (0.65PZTx–0.35PNN) ceramics exhibited a morphotropic phase boundary at approximately x=0.58–0.59. The 0.65PZT58–0.35PNN ceramics sintered at 1200°C exhibited the high piezoelectric properties of d33=605pC/N, kp=0.61, and ɛ3T/ɛ0=3600. The sintering temperature of the PZT58–PNN ceramics decreased from 1200 to 850°C with the addition of a small amount of CuO. The CuO reacted with the PbO and formed a liquid phase during sintering, which assisted in the densification of the specimens. Most of the Cu2+ ions existed in the CuO second phase, thereby preventing any possible hardening effect due to the Cu2+ ions. The Curie temperature of the 0.65PZT58–0.35PNN ceramic was approximately 200°C and was not altered by the addition of CuO. The d33, kp, and ɛ3T/ɛ0 values of the 0.65PZT58–0.35PNN ceramics were considerably increased with the addition of CuO and similar results were also observed for the 0.65PZT59–0.35PNN ceramics. In particular, 1.0 mol% CuO‐added 0.65PZT58–0.35PNN ceramics sintered at 900°C exhibited the high piezoelectric properties of d33=620 pC/N, kp=0.64, and ɛ3T/ɛ0=3750. Moreover, the reaction between the Ag electrode and the Cu‐added 0.65PZT58–0.35PNN ceramic sintered at 900°C was negligible.

Microstructure and Piezoelectric Properties of (K0.5Na0.5)NbO3–BaTiO3 Lead‐Free Piezoelectric Ceramics Modified by B2O3–CuO

A combined sintering aid mixture of B2O3 and CuO for lead‐free piezoelectric ceramics having the composition 0.95K0.5Na0.5NbO3–0.05BaTiO3 (KNN‐BT) is introduced. The effects of the sintering aid mixture of 0.6B2O3–0.4CuO on the sintering behavior, microstructure, and electrical properties of KNN‐BT are investigated. Adding 2 wt% of the sintering aid mixture can effectively broaden the narrow sintering temperature range having a size of 20°C to above 50°C and increase the grain size of samples as well as maintain the high density of samples sintered at a low temperature. The increase in grain size contributes to an improvement in electrical properties. High piezoelectric properties of d33=205 pC/N, kp=38.0%, Qm=119, ɛ33T/ɛ0=1254, and tan δ=0.0264 are obtained for a KNN‐BT‐2wt% (B2O3–CuO) sample sintered at 1120°C.

Polymorphic phase transition and excellent piezoelectric performance of (K0.55Na0.45)0.965Li0.035Nb0.80Ta0.20O3 lead-free ceramics

A lead-free ceramic with the composition (K0.55Na0.45)0.965Li0.035Nb0.80Ta0.20O3 was found having an outstanding piezoelectric performance. It possesses high piezoelectric properties of d33=262 pC/N, kp=0.53, k33=0.63, and k31=0.31 with ε′=1290 and tan δ=0.019 at room temperature. In spite of the orthorhombic-tetragonal polymorphic phase transition around 30 °C, temperature stability of the electromechanical coupling coefficients is very good over the common usage temperature interval between −40 and 85 °C. Furthermore, the piezoelectric properties remain almost unchanged in the severe thermal aging test down to −150 °C and up to about 300 °C. It is suggested that the outstanding piezoelectric performance of this ceramic can be largely ascribed to the phase coexistence in a wide temperature range and the Ta-rich composition.

Phase Transition, Piezoelectric Properties, and Thermal Stability of (1−x−y)BiScO3–yBiGaO3–xPbTiO3 Ceramics

(1−x−y)BiScO3–yBiGaO3–xPbTiO3 (BGSPTx/y) piezoelectric ceramics were synthesized using the conventional oxide process. The phase diagram around the ternary morphotropic phase boundary of BGSPTx/y has been determined. It was found that BGSPT0.55/0.19 ceramics possessed a high Curie temperature (TC) of about 502°C, while maintaining their rather high piezoelectric properties of d33=152 pC/N and d31=−60 pC/N. In addition, BGSPT0.62/0.15 ceramics showed good resistance to thermal depoling up to about 480°C. The excellent thermal stability of BGSPTx/y may allow this material to be used as stable piezoelectric sensors for extreme high‐temperature environments.

Microstructure and piezoelectric properties of lead-free (1−x)(Na0.5K0.5)NbO3-xCaTiO3 ceramics

The crystal structure of (1−x)(Na0.5K0.5)NbO3-xCaTiO3 ceramics began to change from orthorhombic to tetragonal at x≥0.03, then became a morphotropic phase boundary in which both the orthogonal and tetragonal phases coexisted at 0.03<x<0.07, and was converted to tetragonal structure at x≥0.07. The Curie temperature decreased with increasing x and the specimen became a relaxor at x≥0.03. A dense microstructure with large grains was developed at 0.04<x<0.07 due to liquid phase sintering. The relative density, grain size, and liquid phase considerably influenced the piezoelectric properties of the specimens. High piezoelectric properties of d33=241, kp=0.41, and ε3T/εo=1316 were obtained from the 0.95NKN-0.05CT ceramics sintered at 1050 °C for 2 h, indicating that the 0.95NKN-0.05 ceramic is a good candidate material for lead-free piezoelectric ceramics.

Low‐Temperature Sintering and Piezoelectric Properties of CuO‐Added 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 Ceramics

The sintering temperature of 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 (NKN–BT) ceramics needs to be decreased below 1000°C to prevent Na2O evaporation, which can cause difficulties in poling and may eventually degrade their piezoelectric properties. NKN–BT ceramics containing CuO were well sintered at 950°C with grain growth. Poling was easy for all specimens. Densification and grain growth were explained by the formation of a liquid phase. The addition of CuO improved the piezoelectric properties by increasing the grain size and density. High piezoelectric properties of d33=230 pC/N, kp=37%, and ɛ3T/ɛ0=1150 were obtained from the specimen containing 1.0 mol% of CuO synthesized by the conventional solid‐state method.

Microstructure and Piezoelectric Properties of 0.95(Na0.5K0.5)NbO3–0.05SrTiO3 Ceramics

The 0.95(Na0.5K0.5)NbO3–0.05SrTiO3 (0.95NKN–0.05ST) ceramics formed in this study had a porous microstructure with small grains and low piezoelectric properties due to their low density. However, when a small amount of Na2O was intentionally subtracted from the 0.95NKN–0.05ST ceramics, a liquid phase was formed, which led to increased density and grain size. Piezoelectric properties were also improved for the Na2O‐subtracted 0.95NKN–0.05ST ceramics. The increased density and grain size were responsible for the enhancement of the piezoelectric properties. In particular, the 0.95(Na0.49K0.5)NbO2.995–0.05ST ceramics showed high piezoelectric properties of d33=220, kp=0.4, Qm=72, and ɛ3T/ɛo=1447, thereby demonstrating their promising potential as a candidate material for application to lead‐free piezoelectric ceramics.