High Temperature Piezoceramics Research Articles

Multiscale Structural Engineering Boosts Piezoelectricity in Na0.5Bi2.5Nb2O9-Based High-Temperature Piezoceramics.

High-temperature piezoelectric materials, which enable the accurate and reliable sensing of physical parameters to guarantee the functional operation of various systems under harsh conditions, are highly demanded. To this end, both large piezoelectricity and high Curie temperature are pivotal figures of merit (FOMs) for high-temperature piezoceramics. Unfortunately, despite intensive pursuits, it remains a formidable challenge to unravel the inverse correlation between these FOMs. Herein, a conceptual material paradigm of multiscale structural engineering was proposed to address this dilemma. The synergistic effects of phase structure reminiscent of a polymorphic phase boundary and refined domain morphology simultaneously contribute to a large piezoelectric coefficient d33 of 30.3 pC/N and a high Curie temperature TC of 740 °C in (LiCeNd) codoped Na0.5Bi2.5Nb2O9 (NBN-LCN) ceramics. More encouragingly, the system has exceptional thermal stability and is nonsusceptible to mechanical loading. This study not only demonstrates that the high-performance and robust NBN-LCN high-temperature piezoceramics hold great potential for implements under harsh conditions but also opens an avenue for integrating antagonistic properties for the enhancement of the collective performance in functional materials.

Simultaneously achieved high piezoelectricity and resistivity in CaBi2Nb2O9-based ceramics with high curie temperature

To guarantee the functional operation of high-temperature piezoceramics in harsh circumstances, both large piezoelectricity and superior resistivity are prerequisites. However, it remains a formidable challenge to achieve these objects. Herein, we report Ce-doped CaBi2Nb2O9-based high-temperature polycrystals, which can simultaneously deliver a high piezoelectric coefficient d33 of 21.8 pC/N and decent resistivity ρ of 7.1 × 107 Ω﹒cm at 500 °C, along with a high Curie temperature of 916 °C. More encouragingly, the materials are also gifted with exceptional thermal stability ( < 10% variation of d33 in a broad range from ambient temperature up to 900 °C). In-depth multiscale structural characterizations unveil that the outstanding comprehensive performance of Ce-doped CaBi2Nb2O9-based ceramics originate from the synergistic effects of refined grain size and domain morphology, and reduced defect concentration. This work not only demonstrates that CaBi2Nb2O9-based ceramics hold enormous potential for high-temperature implements, but also offers prospects to exploit high-performance high-temperature piezoceramics.

Quenching and Electrical Current Poling Effect on Improved Ferroelectric and Piezoelectric Properties in BiFeO3-Based High-Temperature Piezoceramics.

The effects of quenching on the structural, electrical, dielectric, ferroelectric (FE), and piezoelectric properties are investigated systematically in the 0.85BiFe1-xCrxO3-0.15BaTi1-xMnxO3 (0 ≤ x ≤ 0.03) ceramics. Optimal piezoelectricity and FE Curie temperature are obtained through optimized quenching rate and temperature. Quenching effect on piezoelectricity is especially significant for the samples near morphotropic phase boundaries (MPB), which can be ascribed to quenching-induced changes in phase ratio (rhombohedral and tetragonal phase) and domain structure/defect dipole orientation. Moreover, a new poling method, that is, cooling the sample at a constant dc current across FE TC, is established to improve the piezoelectricity. This work not only reveals the possible mechanism of quenching effect on the improved piezoelectricity in the BFO-based piezoceramics (especially near the MPB) but also suggests an electric current poling strategy for improving piezoelectricity by suppressing the defect dipole effects in BFO-based and even other piezoelectrics.

Optimization of calcination temperature of lead-free BiFeO3–BaTiO3 high-temperature piezoceramics

0.7BiFeO3-0.3BaTiO3+1mol% MnO2(0.7BFO-0.3BTO) ceramics were synthesized by conventional solid-state powder method under different calcination temperatures (Tcal) between 770 and 830 °C. The phase structure, microstructure, and ferroelectric and piezoelectric properties changed greatly depending on the applied Tcal. Benefitting from the formation of low defect levels and large grain size and an appropriate morphotropic phase boundary (MPB) with the rhombohedral-to-pseudocubic phase ratio = 49.1 : 50.9, BFO-BTO ceramics calcined at 785 °C showed the best ferroelectric, piezoelectric, and insulating properties (Pr = 23.1 μC/cm2, EC = 25.8 kV/cm, d33 = 167.8 pC/N, kp = 0.342%). Above Tcal = 800 °C, however, the ferroelectric and piezoelectric properties deteriorated because volatilization of Bi and reduction of Fe caused a poor insulating property and high degree of chemical inhomogeneity. Moreover, the ceramics calcined at 785 °C showed a high Curie temperature (TC) of 509.2 °C and excellent thermal aging resistance of d33 up to 450 °C, demonstrating great potential for use in high-temperature applications.

Superior high-temperature piezoelectric performances in BF-PT-BT ceramics via electric field constructed phase boundary

Owing to the mutual restriction between piezoelectric coefficient (d33) and Curie temperature (Tc), the discovery of high-temperature piezoceramics with large d33 is highly desirable but challenging. Here, BiFeO3-BaTiO3-PbTiO3 (BF-BT-PT) ternary system is redesigned by combining the low lattice distortion of BF-BT perovskites and rhombohedral-tetragonal coexistence of BF-PT phase boundary. As a result, excellent comprehensive piezoelectric properties with a large d33 of ∼380 pC/N and a high Tc of ∼483 °C are obtained in a tetragonal composition close to the triple point. Interestingly, even though a c/a ratio as large as 1.04 can be detected in the virgin sample, hierarchical domains that macrodomains composed of nanosized stripe domains can be found. The tetragonal phase could partly transform into a monoclinic phase under electric field according to in-situ high-energy synchrotron X-ray diffraction measurement, constructing a field-induced morphotropic phase boundary. The large lattice distortion and unstable phase structure simultaneously contribute to the high Tc, and large d33 for the studied BF-BT-PT ceramics, respectively, showing great potential for high-temperature sensors and transducers.

A new method for improving the stability of high temperature piezoelectric properties in BiFeO3–BaTiO3 ceramics by regulating the relaxor transition

The piezoelectric responses were fluctuated with rising temperature for most of piezoceramics, which could affect the precision of service equipment directly. However, very few reports about improving stability of high temperature piezoelectric properties could be found out. In this work, the stability of high temperature piezoelectric properties for 0.7BFO-0.3BT ceramics was improved, which could be realized by suppressing relaxor phase transition. The ferroelectric-relaxor transition around 200 °C in 0.7BFO-0.3BT ceramics has an accelerating effect to depolarization process, which was inhibited by doping CuO, Li2CO3 and ZnO. The frequency dependency of permittivity was decreased in the temperature range of 150–350 °C after doping, and the degradation of piezoelectric properties was suppressed. Contrary to above mentioned doping ceramics, fluctuant high temperature piezoelectric properties because of the aggravated relaxor phase transition expressed after doping MnO2. As a result, the doped 0.7BFO-0.3BT ceramics with excellent electrical properties and improved stability of high temperature piezoelectric properties from room temperature to Curie temperature were obtained. The method for improving stability of high temperature piezoelectric properties opened a new window for extending the application range of high temperature piezoceramics.

Ion-Pair Engineering-Induced High Piezoelectricity in Bi4Ti3O12-Based High-Temperature Piezoceramics.

High-temperature piezoceramics are highly desirable for numerous technological applications ranging from the aerospace industry to the nuclear power sector. However, it is a grand challenge to achieve excellent piezoelectricity and high Curie temperature (Tc) simultaneously because there is a contradiction between the large piezoelectric coefficient and high Curie temperature in piezoceramics. Here, we provide a perspective via B-site ion-pair engineering to design piezoceramics with high performance for high-temperature applications. In bismuth-layered Bi4Ti2.93(Zn1/3Nb2/3)0.07O12 ceramics, high piezoelectricity of d33 = 30.5 pC/N (more than four times higher than that of pure Bi4Ti3O12 (d33 = 7.3 pC/N) ceramics) in conjunction with excellent thermal stability, high Curie temperature Tc = 657 °C, and large dc resistivity of ρ = 1.24 × 107 Ω·cm at 500 °C (three orders of magnitude larger than that of the pure Bi4Ti3O12 ceramics) are achieved by B-site Nb5+-Zn2+-Nb5+ ion-pair engineering. Excellent piezoelectricity is ascribed to sufficient orientation of the fine lamellar ferroelectric domain with the introduction of Nb5+-Zn2+-Nb5+ ion-pairs. The good temperature stability of d33 originates from the stability of the crystal structure and the robustness of the oriented ferroelectric domain. The significantly improved resistivity is due to the restricted mobility of oxygen vacancies. This work presents a brand-new technique for achieving high-temperature piezoceramics with high performance by B-site ion-pair engineering.

Piezoelectricity, thermal stability, and fatigue resistance in Nb and Ta-doped Bi4Ti3O12 high-temperature piezoceramics

The effect of Nb/Ta donor doping on the piezoelectricity, thermal stability, and fatigue resistance of bismuth titanate Bi4Ti3O12 (BIT) ceramics was investigated in relation to their structural and oxygen vacancy-related electrical properties. As the Nb/Ta doping amount increased, the activation energy of oxygen vacancy conduction increased, indicating a reduction in the concentration of oxygen vacancies. The improved electrical insulating properties of the Nb/Ta-doped Bi4Ti3O12 ceramics (BTNT) with fewer oxygen vacancies, contributed to their effective poling and strong piezoelectricity. Outstanding piezoelectric performance with high piezoelectric constant (39 pC/N) and Curie temperature (690 °C) could be achieved in the 0.005 mol Nb/Ta-doped BTNT ceramic with high density and anisotropic grain growth. The BTNT ceramics exhibited superior thermal aging stability and fatigue resistance compared to the BIT ceramic, suggesting that the reduction of oxygen vacancy defects plays a decisive role in enhancing elevated-temperature-induced and electric-field-induced degradation stabilities.

A simple Bi3+ self-doping strategy constructing pseudo-tetragonal phase boundary to enhance electrical properties in CaBi2Nb2O9 high-temperature piezoceramics

Calcium bismuth niobate (CaBi2Nb2O9, CBN)-based ceramics are promising candidates for high temperature application, the electrical properties of which are commonly enhanced by complex ion substitution or texture processes. Here, we report that high piezoelectricity and high resistivity were achieved in Ca1-xBi2+xNb2O9 by constructing pseudo-tetragonal boundary through a simple strategy of Bi3+ self-doping. At the pseudo-tetragonal boundary, Ca0.96Bi2.04Nb2O9 ceramics maintain high Curie temperature Tc = 942 °C, and show high piezoelectric coefficient d33 = 15.1 pC/N and high resistivity ρdc = 2 × 106 Ω cm (@600 °C). It is proved that the good piezoelectric property mainly originates from the increase of domain density. In addition, Ca0.96Bi2.04Nb2O9 ceramics reveal good thermal depoling performance, remaining 90% of piezoelectricity after thermal depoling at 900 ℃, which is due to small thermal expansion and structural distortion. Our work provides a promising candidate for high temperature applications and an easy way to improve the performance of Aurivillius-type piezoelectric ceramics.

Simultaneously enhanced piezoelectricity and curie temperature in BiFeO3-based high temperature piezoelectrics

We report the structure, dielectric, ferroelectric and piezoelectric properties of Cr-Mn co-doped (1-y)BiFe1-xCrxO3-yBaTi1-xMnxO3 (0≤x≤0.04, 0.2≤y≤0.27) ceramics. By varying both x and y, a series of samples near morphotropic phase boundaries exhibiting both high ferroelectric Curie temperature TC (∼580−643 °C) and relatively large piezoelectric constant d33 are constructed. Especially, the sample with y = 0.24 and x = 0.02 is found to show coexistence of high depolarization temperature Td (∼551 °C) and relatively large d33∼116 pC/N, superior to most of those of BiFeO3 based high-temperature piezoceramics reported previously. The enhanced ferroelectric TC in the Cr-Mn modified samples can be ascribed to the combined effects of large lattice distortion and high tetragonal phase content. These results demonstrate that constructing morphotropic phase boundaries via considering simultaneously the role of lattice distortion might be effective route to realize high-temperature and high piezoelectricity in BiFeO3-based systems.

Achieving remarkable piezoelectric activity in Sb–Mn co-modified CaBi4Ti4O15 piezoelectric ceramics

CaBi4Ti4O15 (CBT)-based Aurivillius high-temperature piezoceramics with different Sb–Mn co-doping amounts were synthesized via the conventional sintering technique. The influences of doping amount on the product were studied via their crystal structure, microstructure, and piezoelectric performance. It is found that an appropriate Sb–Mn co-doping amount can effectively optimize the crystal structure and decrease the oxygen vacancy concentration in CBT ceramics, leading to enhanced electrical properties. Optimized electrical performance with a high Curie temperature (TC) of 792 °C and a remarkable piezoelectric coefficient (d33) of 25 pC/N were achieved at a doping amount (x) of 0.05. Furthermore, this ceramic is found to exhibit an excellent thermal stability, with d33 retaining 88% of its original value after annealing at 600 °C for 2 h. Moreover, this ceramic shows a high electrical resistivity (ρ) of 1.35×108 Ω·cm with a small dielectric loss (tan δ) of 1.7% at 400 °C. Because of such outstanding piezoelectric performance, it is believed that these Sb–Mn co-doped CBT ceramics could be potential candidates for high-temperature piezoelectric applications.

Crystal structure and dielectric properties of layered perovskite-like solid solutions Bi3−x Gdx TiTaO9 (x = 0.0, 0.1, 0.2, 0.3) with high Curie temperature

The Aurivillius phases [Bi2O2][A[Formula: see text][Formula: see text]O[Formula: see text]] are well-known ferroelectrics with high Curie temperatures [Formula: see text]. High-temperature piezoceramics Bi[Formula: see text][Formula: see text]TiTaO9 (BGdTTa, [Formula: see text]= 0.0, 0.1, 0.2, 0.3) were prepared by a solid-state reaction method. The structural and electrophysical characteristics of BGdTTa ceramics have been studied. According to the data of powder X-ray diffraction, all the compounds are single-phase with the structures of two-layer Aurivillius phases ([Formula: see text] = 2) with the orthorhombic crystal lattice (space group A21am). The temperature dependence of the relative permittivity [Formula: see text]/[Formula: see text] ([Formula: see text] of the compounds was measured and showed that the Curie temperature [Formula: see text] of perovskite-like oxides Bi[Formula: see text][Formula: see text]TiTaO9 increases linearly with an increase in the substitution parameter [Formula: see text] to [Formula: see text] = 925[Formula: see text]C. The activation energies of charge carriers have been found in different temperature ranges.

The evolution of structure and electrical properties for BiFeO3–PbTiO3–Ba(Zr0.3Ti0.7)O3 high-temperature piezoceramics near the morphotropic phase boundary

The development of piezoceramics with high Curie temperature and high piezoelectrical performance has always been a long-cherished goal for many researchers. In this work, we have fabricated 0.55BiFeO3-(0.45-x)PbTiO3-xBa(Zr0.3Ti0.7)O3 ternary ceramics near the morphotropic phase boundary (MPB) by conventional solid-state method. XRD patterns indicate that there is an evolution from the tetragonal (T) to pseudo-cubic (PC) phase with BZT content increasing from 0.125 to 0.225. Also, the slim P-E loop transforms into a saturated shape with the decrease of coercive field Ec. Piezoresponse force microscope (PFM) analysis reveals that when x (BZT content) increases, domain density increases. The optimum piezoelectric coefficient d33 (~220 pC/N) is obtained at x = 0.175, while Curie temperature TC and dielectric loss tanδ are 434 °C and 0.019, respectively. These results show that BF-PT-based piezoceramics are competitive candidates in future high-temperature applications of piezoelectric ceramics.

Thermal shock resistance and crack growth behavior of Aurivillius phase Bi4Ti3O12-based ferroelectric ceramics

A type of W/Cr co-doped Bi4Ti3O12 (ab. BTWC) ceramics were synthesized utilizing the traditional solid-state reaction process, and its thermal shock resistance (TSR) as well as the crack growth behavior was systematically investigated by water quenching technology. It can be found by the succeeded fractographic analysis that many edge thermal cracks began to appear in the samples subjected to thermal shock with ΔT ​= ​400 ​°C. According to an integrated TSR model, the critical thermal-shock temperature difference ΔTCwas calculated to be 356 ​°C. Moreover, it can be noticed that the indenter induced crack growth behaviors under thermal shock loads presented three stages, i.e. no growth, large growth, and moderate growth, along with ΔT increasing from 0 ​°C to 700 ​°C. Finally, the asymmetry of P-E hysteresis loops was observed and understood by the orientated polarization of defect dipoles after the sample was thermally shocked, while the water-quenching process above the Curie temperature of the ceramics could lead to a random orientation of the defect dipoles. This research can not only evaluate the service conditions of Bi4Ti3O12 high-temperature piezoceramics, but also understand the failure mechanism of bismuth layer structured ferroelectric ceramics in the case of thermal shock.

Significantly enhanced piezoelectric performance in Bi4Ti3O12-based high-temperature piezoceramics via oxygen vacancy defects tailoring

Bismuth titanate (Bi4Ti3O12, BIT) piezoelectric materials have attracted increasing attention due to their high-temperature applications. However, it is quite challenging to simultaneously achieve outstanding piezoelectric properties and high Curie temperature in BIT-based systems. In this study, oxygen vacancy defects tailoring strategy was utilized to solve this problem, excellent piezoelectric coefficient (32.1 pC/N), and ultrahigh Curie temperature (659 °C) are gotten in Bi4Ti3-x(Mn1/3Nb2/3)xO12 (BTMN) ceramics, which are among the top values in the BIT-based ceramics. More importantly, the (Mn1/3Nb2/3)(4+δ)+ complex-ion modified Bi4Ti3O12-based ceramics are characterized with excellent piezoelectric stability up to 500 °C (d33 > 30.0 pC/N at 500 °C)) and significantly reduced conductivity (only ∼ 10−7 Ω−1 cm−1 at 500 °C). Moreover, enhanced ferroelectricity and good dielectric stability were also obtained. The better comprehensive properties can be ascribed to two aspects. First, the concentration of oxygen vacancy defects is obviously reduced, and their distribution is effectively controlled in BITMN ceramics. Second, the introduction of (Mn1/3Nb2/3)(4+δ)+ complex-ion gives rise to the antiphase boundaries and massive ferroelectric domain walls. This works not only reveal the high potential of BITMN ceramics for high-temperature piezoelectric applications but also deepen the understanding of the structure-properties relationship in BIT-based materials.

Enhanced piezoelectric activity with good thermal stability and improved electrical resistivity in Ta–Mn co-doped CaBi4Ti4O15 high-temperature piezoceramics

Aurivillius phase CaBi4Ti4-x (Ta2/3Mn1/3)xO15 (x = 0–0.1) high-temperature piezoelectric ceramics were fabricated using the conventional solid-state reaction process. The effects of the Ta–Mn co-doping level on the structure, piezoelectric properties and electrical conduction behaviours of the as-prepared CBT (CaBi4Ti4O15) ceramics were explored in detail. It was revealed that the Ta–Mn co-doping efficaciously enhanced the electrical performances of the CaBi4Ti4O15 ceramic, which may be due to optimisation of the crystal structure and a reduction in the oxygen vacancy concentration. The composition with x = 0.04 presented superior electrical properties with an outstanding piezoelectric constant (d33) of 24 pC/N accompanied by a high Curie temperature (TC) of 793 °C, an optimised dielectric loss (tanδ) of 1.5%, and an improved resistivity (ρ) of 4.96 × 108 Ω cm at 400 °C. Moreover, the ceramic exhibited impressive thermal stability with the d33 value maintaining 91.7% of its initial value at room temperature (25 °C) after being annealed at 600 °C for 2 h. The improved performance indicates that the Ta–Mn co-doped CaBi4Ti4O15 ceramic might be a promising candidate for piezoelectric device applications at elevated temperatures.

Crystal structure and dielectric properties of layered perovskite-like solid solutions Bi3−xGdxTiNbO9 (x=0, 0.1, 0.2, 0.3) with high Curie temperature

The Aurivillius phases (APs) [Bi2O2][Formula: see text][[Formula: see text][Formula: see text]][Formula: see text] are well-known ferroelectrics with high Curie temperatures. High-temperature piezoceramics [Formula: see text]GdxTiNbO9(BiGdTiNb, [Formula: see text], 0.1, 0.2, 0.3) were prepared by a solid-state reaction method. The structural and electrophysical characteristics of BiGdTiNb ceramics have been studied. According to the data of powder X-ray diffraction, all the compounds are single-phase with the structures of two-layer APs ([Formula: see text]) with the orthorhombic crystal lattice (space group [Formula: see text]). The temperature dependence of the relative permittivity [Formula: see text] (T) of the compounds was measured and showed that the Curie temperature of perovskite-like oxides [Formula: see text]GdxTiNbO9 increases linearly with an increase in the substitution parameter [Formula: see text] to [Formula: see text]C. The activation energies of charge carriers have been found in different temperature ranges.

Improved electrical properties in Nb/Fe co-modified CaBi4Ti4O15 high-temperature piezoceramics

Nb/Fe co-doped CaBi4Ti4−x(Nb1/2Fe1/2)xO15(CBT) (x = 0, 0.01, 0.02, 0.025, 0.05, 0.075, and 0.1) high-temperature piezoceramics were synthesized using conventional solid-state reaction method. The effects of Nb/Fe doping level on the structure dielectric, ferroelectric and piezoelectric properties were investigated in detail. It was found that Nb/Fe co-doping effectively improved the electrical performances of CBT ceramic. Significant enhancement of piezoelectric coefficient (d33) was acquired at x = 0.02 with a d33 value of 21.6 pC/N, accompanied by a high Curie temperature (TC) of 793 °C and a low dielectric loss (tanδ) of 5.9% at 400 °C. Moreover, the ceramic showed a good thermal stability with a d33 value of 19.3 pC/N after being annealed at 700 °C for 2 h, keeping 89.4% of its initial value at room temperature. These results indicated great potentials of the Nb/Fe co-doped CBT ceramics for high-temperature piezoelectric applications.

Ultra-broad temperature insensitive ceramics with large piezoelectricity by morphotropic phase boundary design

Improving the operating characteristics of piezoelectric devices in high temperature environments urgently requires the development of piezoceramics with both high piezoelectric coefficient and excellent temperature stability. However, it is difficult for existing piezoceramics to take care of both at the same time. Generally, high piezoelectricity can be obtained at morphotropic phase boundary (MPB) in the binary systems, such as PbZrO3–PbTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3, but the temperature stability is unsatisfactory, which seriously restricts the practical application. Here, an optimum composition having excellent comprehensive properties is constructed by designing multiple MPBs in the novel xPb(In1/2Nb1/2)O3-yBiScO3–zPbTiO3 ternary system. When x = 0.04, y = 0.345 and z = 0.615, the specimen has a high piezoelectric coefficient d33 of 478 pC/N at 200 °C, meanwhile, the fluctuation of d33 is less than ± 10% over an ultra-broad temperature range of 50–350 °C. Combined with a variety of in situ analysis techniques, it can be determined that the temperature-insensitive high piezoelectric coefficient is related to the multiple MPBs design, which is beneficial to the optimization of the hierarchical domain configuration. The developed phase boundary design strategy paves a new way to building next generation high performance high temperature piezoceramics.

Structural distortion, piezoelectric properties, and electric resistivity of A-site substituted Bi3TiNbO9-based high-temperature piezoceramics

High-temperature piezoceramics Bi3-xCexTiNbO9+δ (BCTN-100x, x=0, 0.02, 0.04, 0.06, 0.07, 0.08, 0.10) were prepared by a solid-state reaction method. The crystal structure, microstructure, dielectric behaviour, piezoelectricity, temperature stability and electrical conduction mechanisms of BCTN-100x ceramics were studied. All Ce-doped Bi3TiNbO9 ceramics had a single Aurivillius phase structure. Ce substitution influenced the crystal structure, leading to a high piezoelectric constant (d33=17 pC/N) but decreasing the Curie temperature slightly (TC=883 °C). The resistivity of Ce-doped BTN ceramics increased by two orders of magnitude compared with that of the pure BTN. Furthermore, the dc and ac conduction mechanisms were studied, indicating that the conduction mechanism is closely related to temperature for dc and ac conduction behaviour. In addition, we analysed the dielectric relaxation processes and attributed them to the motion of oxygen vacancies, which deviates from the ideal Debye-model.