ZrO3 Lead-free Ceramics Research Articles

High piezoelectricity in (K,Na)(Nb,Sb)O3–(Bi,La,Na,Li)ZrO3 lead-free ceramics

A new lead-free piezoelectric system of (1 − x)(K0.48Na0.52+y )(Nb0.95Sb0.05)O3–x(Bi0.8La0.2)0.5(Na0.8Li0.2)0.5ZrO3 [(1 − x)KNa y NS–xBLNLZ] were prepared using the conventional solid-state sintering method. The effects of BLNLZ content and Na excess on the microstructure and electrical properties of the ceramics were investigated. It was found that an enhanced dielectric, ferroelectric, and piezoelectric behavior has been attained by successfully constructing the rhombohedral–tetragonal phase boundary in the ceramics with x = 0.04. The small Na excess can greatly improve ceramics properties due to the increase of abnormal grain growth caused by the formation of a small amount of liquid phase. As a result, the ceramic with x = 0.04 and y = 0.004 has optimum electrical properties of d 33 ~470 pC/N, k p ~50 %, 2P r ~32.3 μC/cm2, and 2E c ~14.2 kV/cm, together with a Curie temperature of ~210 °C. The giant d 33 of this ceramic system could be comparable with the most of the reported results about the alkali niobate-based lead-free piezoceramics. It was believed that such an excellent piezoelectricity of this material system will promote the development of KNN-based lead-free ceramics.

Phase transition and piezoelectric properties of dense (K0.48,Na0.52)0.95Li0.05SbxNb(1−x)O3-0.03Ca0.5(Bi0.5,Na0.5)0.5ZrO3 lead free ceramics

A newly designed system of (K0.48Na0.52)0.95Li0.05SbxNb(1−x)O3- 0.05Ca0.5(Bi0.5Na0.5)0.5ZrO3 (KNLSxN-CBNZ) lead-free ceramics were prepared by conventional solid state reaction method. Effects of antimony (Sb) content on their phase structure, microstructure, electrical properties and sinterability were systematically studied. It is found that ceramics with 0.06 ≤ x ≤ 0.08 possess a rhombohedral–tetragonal (R-T) phase boundary, as confirmed by the results of temperature dependence of dielectric properties and X-ray diffraction patterns. In addition, the ceramic with x = 0.06 has optimum piezoelectric properties (d33 = 267 pC/N, kp = 45.2%, εr = 1836, tan δ = 3.32%, Tc = 253 °C) with a quite high density (ρ = 4.63 g/cm3). As a result, we believe that the ceramic system is a promising lead-free piezoelectric candidate for practical applications.

Phase Transitional Behavior and Dielectric Properties of (Ba,Ca)(Ti,Zr)O3–Bi(Zn,Zr)O3 Lead-Free Ceramics

The (1-x)(Ba0.98Ca0.02)(Ti0.95Zr0.05)O3–xBi(Zn0.5Zr0.5)O3 [BCZT–xBZZ, x = 0.005–0.06] lead-free solid solution ceramics were synthesized by a conventional solid state reaction method. The effect of Bi(Zn0.5Zr0.5)O3 addition on the crystal structure, microstructure, relaxor behavior and dielectric properties of the (Ba0.98Ca0.02)(Ti0.95Zr0.05)O3 ceramics has been studied. X-ray diffraction shows that all the ceramics possess a single phase of perovskite structure. The BCZT–xBZZ ceramics change from tetragonal phase to pseudocubic phase with the content of BZZ increasing. Moreover, the grain size is affected by BZZ addition. The BCZT–xBZZ ceramics become considerably dense with the proper amount of BZZ introduction. The relative permittivity ϵr and loss tangent tanδ vary with the increasing BZZ content. Temperature dependence of the dielectric properties indicates that as the concentration of BZZ increases, the BCZT–BZZ solid solution ceramics exhibit more relaxor-like behavior. Furthermore, the BCZT–xBZZ ceramics exhibit low dielectric loss and excellent dielectric temperature stability in a wide temperature range, which indicates a potential application in devices under comparably high-temperature environment.

High piezoelectric response in KNNS–xBNKZ lead-free ceramics

(1 − x)(K0.49Na0.51)(Nb0.95Sb0.05)O3–xBi0.5(Na0.82K0.18)0.5ZrO3 (KNNS–xBNKZ, x = 0–0.05) lead-free piezoelectric ceramics were prepared by a solid state reaction route. The effect of BNKZ on the phase transition and electrical properties of the ceramics was investigated. The XRD patterns indicated the formation of a single perovskite phase with the structure changing from orthorhombic to tetragonal to pseudo-cubic by increasing BNKZ doping amount x. A coexistence of orthorhombic and tetragonal phases with 0.03 ≤ x ≤ 0.04 was obtained, leading to strongly enhanced electrical properties of piezoelectric constant d 33 ≥ 400 pC/N and dielectric constant ɛ 33 /ɛ 0 > 2000. Together with relatively low dielectric loss (tanδ < 4 %) and normally high Curie temperature (T c > 200 °C), this lead-free piezoelectric ceramics should be a good candidate for replacing toxic lead-based ones.

Phase structure and electrical properties of 0.965(K0.45Na0.55)0.95Ag0.05(Nb1−x Sb x )O3–0.035Bi0.5(Na0.5Li0.5)0.5ZrO3 lead-free ceramics

Lead-free 0.965(K0.45Na0.55)0.95Ag0.05(Nb1−x Sb x )O3–0.035Bi0.5(Na0.5Li0.5)0.5ZrO3 (KNANS x –BNLZ) ceramics were synthesized using the conventional solid-state reaction method, and the effects of Sb5+ content on the phase structure and electrical properties of the samples were investigated. The results showed that the samples endure a phase transition from orthorhombic–tetragonal to rhombohedral–tetragonal (R–T) phases with increasing Sb content. The R–T phase boundary was observed in the composition range of 0.03 ≤ x ≤ 0.05, and then the enhanced electrical properties of d 33 = 345 pC/N and k p = 38.5 % were obtained in the ceramics with x = 0.04, which is mainly ascribed to the involved R–T phase boundary together with a dense microstructure.

Composition design and electrical properties in (1-y)(K0.40Na0.60)0.985Li0.015(Nb1−xSbx)O3-yBi0.5Na0.5ZrO3 lead-free ceramics

To realize the enhancement in piezoelectric activities, the composition-induced phase boundaries in (1-y)(K0.40Na0.60)0.985Li0.015(Nb1−xSbx)O3-yBi0.5Na0.5ZrO3 lead-free ceramics were designed and fabricated by the conventional solid-state method. We presented the evolutions of their phase structure, microstructure, and electrical properties with the change of Sb5+ and Bi0.5Na0.5ZrO3 contents. A rhombohedral-tetragonal phase boundary was successfully built in the composition region of 0.04 ≤ x ≤ 0.09 (y = 0.025) and 0.025 ≤ y ≤ 0.035 (x = 0.06), and then the desirable piezoelectric coefficients and bipolar strains (e.g., d33∼390 pC/N, kp∼0.45, Smax∼0.2%, and TC∼250 °C) were simultaneously induced. We think that this may provide a direction of designing high-performance (K,Na)NbO3-based ceramics.

Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O3 lead-free ceramics

Li-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540°C down to about 1400°C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d33 (512pC/N) and a planar electromechanical coupling factor kp (0.49), which have the characteristics of soft Pb(Zr,Ti)O3 (PZT) piezoceramic, on the other hand, the mechanical quality factor Qm is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature.

Influence of K/Na ratio on phase structure and electrical properties of 0.96 (K x Na1−x ) NbO3-0.04 (Bi0.5Na0.5) ZrO3 lead-free ceramics

To investigate the influence of K/Na ratio on the phase structure and electrical properties, 0.96 (K x Na1−x ) NbO3-0.04 (Bi0.5Na0.5) ZrO3 lead-free piezoceramics with x = 0.35 ~ 0.60 were prepared by a conventional solid-state reaction method. The results indicate that a typical phase boundary of orthorhombic-tetragonal (O-T) exists at x = 0.39–0.55 by refining the K/Na ratio. The grain size of the ceramics becomes much larger as the K/Na increases, and the chemical compositions well keep in the ceramic matrix. The ceramics with x = 0.39 show enhanced electrical properties (e.g., d 33 = 275 pC/N, k p = 34.5 %, T C = 330 °C,P r = 27.5 μC/cm2, and E C = 10.5 kV/cm). It is considered that the observed enhanced piezoelectricity should be ascribed to the phase coexistence of O and T phases of the ceramics.

Two-step sintering of new potassium sodium niobate ceramics: a high d₃₃ and wide sintering temperature range.

In this work, the two-step sintering technique is used to realize a high piezoelectric constant (d33) and wide sintering temperature range (T(S)) in the 0.955(K(0.42)Na(0.58))(Nb(0.96)Sb(0.04))O3-0.045(Bi(0.5)K(0.5))(0.90)Zn(0.10)ZrO3 lead-free ceramics. Dense microstructures were developed in the ceramics by two-step sintering. In the T(S) range of 800-1130 °C, the rhombohedral-tetragonal phase boundary was well maintained, and these ceramics possess enhanced dielectric, ferroelectric, and piezoelectric properties. It is of great interest to note that a d33 of 323-416 pC/N could be attained in a temperature gap range of 330 °C. We believe that the two-step sintering could both widen the sintering temperature and obtain a high d33 for this material system.

New potassium-sodium niobate material system: a giant-d₃₃ and high-T(C) lead-free piezoelectric.

In this work, we elucidate the influence of Bi(0.5)Li(0.5)ZrO3 (BLZ) content on the phase structure, microstructure, and electrical properties of (1 -x)K(0.40)Na(0.60)Nb(0.965)Sb(0.035)O3-xBi(0.5)Li(0.5)ZrO3 lead-free ceramics. We simultaneously achieved a giant d33 and a high T(C) in this material system. The coexistence of rhombohedral and tetragonal phases is responsible for such a large d33 in the ceramics with BLZ contents (x) ranging from 0.025 to 0.035. Doping with BLZ not only induces the formation of the phase boundary, but also maintains a high T(C). The ceramic with x = 0.03 shows an enhanced piezoelectric behaviour (d33 ~ 400 pC N(-1) and k(p) ~ 0.47) together with a high T(C) of 292 °C. A good temperature stability for ferroelectricity and piezoelectricity is also observed in these ceramics. This study is the first time that such a good comprehensive performance has been obtained in potassium-sodium niobate materials. We believe that this type of material system possessing giant-d33 and high-T(C) is a promising candidate for use in high-temperature piezoelectric devices.

Phase structure and electrical properties of (K0.5Na0.5)NbO3–(Bi0.5Na0.5)ZrO3 lead-free ceramics with a sintering aid of ZnO

0.95(K0.5Na0.5)NbO3–0.05(Bi0.5Na0.5)ZrO3–xZnO (KNN–BNZ–xZnO) lead-free piezoceramics were prepared by the conventional solid-state method, and effects of ZnO content on their phase structure, microstructure, and electrical properties were studied. The ceramics with x=0.01 possess the mixture of both rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries. Their grain size becomes more homogenous and much smaller with the addition of ZnO. Enhanced dielectric and piezoelectric properties (e.g., d33=320pC/N, kp=0.484, TC=320°C) were observed in the ceramic with x=0.01. These results show that such a material system belongs to be a promising lead-free piezoelectric material.

Phase structure, piezoelectric properties, and stability of new K0.48Na0.52NbO3–Bi0.5Ag0.5ZrO3 lead-free ceramics

In this work, (1 − x)(K0.48Na0.52)NbO3–x(Bi0.5Ag0.5)ZrO3 [(1 − x)KNN–xBAZ] lead-free piezoceramics was prepared by the conventional solid-state method, and a new phase boundary consisting of three phases [e.g., rhombohedral, orthorhombic, and tetragonal (R–O–T) phases] has been constructed by adding both (Bi0.5Ag0.5)2+ and Zr4+. The ceramic with x = 0.05 possesses an R–O–T phase coexistence. A large d 33 of ~347 pC/N and a high T C of ~318 °C have been shown in the ceramic with x = 0.05. In addition, such a ceramic also possesses enhanced thermal and temperature stability of piezoelectricity and ferroelectricity. Both the phase boundary and the grain size play a critical role in large piezoelectricity and good stability. We think that this material belongs to be one of the promising candidates for the high-temperature piezoelectric devices.

Wide phase boundary zone, piezoelectric properties, and stability in 0.97(K0.4Na0.6)(Nb1-xSbx)O3-0.03Bi0.5Li0.5ZrO3 lead-free ceramics.

In this work, the rhombohedral (R) and tetragonal (T) phase boundary of the 0.97(K0.4Na0.6)(Nb1-xSbx)O3-0.03Bi0.5Li0.5ZrO3 piezoceramics has been attained in a wide composition range of 0.035 ≤ x ≤ 0.08, and the Sb(5+) could simultaneously shrink its TR-O and TO-T. A giant d33 of 380-405 pC N(-1) and a TC of 200-292 °C have been observed in the ceramics with the coexistence of both R and T phases. In addition, the ceramics with 0.035 ≤ x ≤ 0.08 also show a good thermal stability of the d33, and an enhanced temperature stability of ferroelectricity could be observed in the ceramic with x = 0.035. As a result, adding the optimum antimony content is an efficient way to promote the electrical properties of potassium-sodium niobate ceramics with the R-T phase boundary.

Large d33 in (K,Na)(Nb,Ta,Sb)O3-(Bi,Na,K)ZrO3 lead-free ceramics

To protect the environment and human health, it is necessary to develop high-performance lead-free piezoceramics to replace the lead-based ones in some electronic devices. Here we report first a large piezoelectricity in (K,Na)NbO3-based lead-free piezoceramics prepared by the conventional solid-state method. The rhombohedral–tetragonal phase boundary is observed in the ceramics with a composition of 0.04 ≤ x ≤ 0.06. Those ceramics with 0.01 ≤ x ≤ 0.06 possess a good comprehensive performance of d33 (380–460 pC N−1) and TC (170–287 °C). Moreover importantly, a peak d33 of ∼460 pC N−1 is shown in the ceramic with x = 0.04, which is superior to all other reported results of KNN-based ceramics, including the reported results by Saito et al. (Nature, 2004, 432, 84). We believe that such a material system is a very promising candidate for potassium–sodium niobate piezoceramics.

New lead-free piezoelectric ceramics based on (K0.48Na0.52)(Nb0.95Ta0.05)O3–Bi0.5(Na0.7K0.2Li0.1)0.5ZrO3

(1 - x)(K0.48Na0.52)(Nb0.95Ta0.05)O3-xBi0.5(Na0.7K0.2Li0.1)0.5ZrO3 lead-free piezoelectric ceramics with a new type of phase boundary have been designed and fabricated. This phase boundary lies in the compositional range of 0.04 ≤ x ≤ 0.05, and is formed by the coexistence of the rhombohedral, orthorhombic, and tetragonal phases. Interestingly, we found that the ferroelectric, dielectric, and piezoelectric properties of the ceramics with compositions near the phase boundary are significantly enhanced. In particular, the ceramic with x = 0.045 shows the best piezoelectric behavior of d33 ∼ 290 pC/N and kp ∼ 0.42 among all the compositions studied in this work, and it also exhibits a good thermal stability at annealing temperatures of ≤270 °C. All these results indicate that such a material system is a good candidate for lead-free piezoelectric applications in the future.

Dielectric and piezoelectric properties of (Bi,Na,Li)TiO3–Ba(Ti,Zr)O3 lead-free ceramics

The lead free ceramics of two different stoichiometric 0.9(Bi0.5Na0.5)TiO3-0.1Ba(Ti1−x Zr x )O3 (abbreviated as BNBTZ-100x, x = 0, 0.045, 0.050, 0.055, 0.060) and 0.9(Bi0.5Na0.5−y Li y )TiO3-0.1Ba(Ti0.945Zr0.055)O3 (abbreviated as BNLBTZ-100y, y = 0, 0.015, 0.025, 0.035, 0.05, 0.075, 0.10, 0.125) compositions were prepared by the conventional ceramic fabrication technique. The crystal structure, dielectric and piezoelectric properties of the ceramics were investigated. All the ceramics formed single-phase solid solutions with tetragonal pervoskite structure, which was affected obviously by the addition of Zr and Li. The T m of the BNBZT-100x ceramics trends to increase whereas the T d trends to decrease as Zr content increases. And the T d of the BNLBZT-100y increases from 107 to 157 °C when y increases from 0 to 0.015, but decreases sharply as y increases further. The d 33 and k p of the BNBTZ-100x ceramics tend to increase with the addition of Zr. The maximum values of d 33 and k p, 156 pC/N and 18.9%, are obtained when x = 0.055. The d 33 of the BNLBTZ-100y ceramics keep almost unchanged when y increases from 0 to 0.035. And maximum value of k p, 16.3%, of the BNLBTZ-100y ceramics is obtained when y = 0.015.