Recent development in lead-free perovskite piezoelectric bulk materials

High recoverable energy density (Wrec ∼ 2.1 J/cm3) was obtained in (0.7 – x)BiFeO3-0.3BaTiO3-xBi(Zn2/3Nb1/3)O3 + 0.1 wt % Mn2O3 (BF-BT-xBZN, x = 0.05) lead-free ceramics at <200 kV/cm. Fast discharge speeds (<0.5 μs), low leakage (∼10–7 A/cm2), and small temperature variation in Wrec (∼25% from 23 to 150 °C) confirmed the potential for these BiFeO3-based compositions for use in high energy density capacitors. A core–shell microstructure composed of a BiFeO3-rich core and BaTiO3-rich shell was observed by scanning and transmission electron microscopy which may contribute to the high value of energy density. In addition, for x = 0.005, a large electromechanical strain was observed with Spos = 0.463% and effective d33* ∼ 424 pm/V, suggesting that this family of ceramics may also have potential for high strain actuators.

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High Energy Storage Density and Large Strain in Bi(Zn2/3Nb1/3)O3-Doped BiFeO3–BaTiO3 Ceramics

Lead-based electroceramics such as Pb(Zr.Ti)O3 (PZT) and its derivatives have excellent piezoelectric, pyroelectric and energy storage properties and can be used in a wide range of applications. Potential lead-free replacements for PZT such as potassium sodium niobate (KNN) and sodium bismuth titanate (NBT) have a much more limited range of useful properties and have been optimized primarily for piezoelectric applications. Here, we review the initial results on a new generation of lead-free electroceramics based on BiFeO3-BaTiO3 (BF-BT) highlighting the essential crystal chemistry that permits a wide range of functional properties. We demonstrate that with the appropriate dopants and heat treatment, BF-BT can be used to fabricate commercially viable ceramics for applications, ranging from sensors, multilayer actuators, capacitors and high-density energy storage devices. We also assess the potential of BF-BT-based ceramics for electrocaloric and pyroelectric applications.

https://www.worldscientific.com/doi/pdf/10.1142/S2010135X18300049

BiFeO3-BaTiO3: A new generation of lead-free electroceramics

Recent advances in lead-free dielectric materials for energy storage

Energy storage materials and their applications have attracted attention among both academic and industrial communities. Over the past few decades, extensive efforts have been put on the development of lead-free high-performance dielectric capacitors. In this review, we comprehensively summarize the research progress of lead-free dielectric ceramics for energy storage, including ferroelectric ceramics, composite ceramics, and multilayer capacitors. The results indicate that dielectric capacitors with both high energy density and high efficiency are feasible using the materials providing high breakdown electric field and a slim hysteresis loop. This article also lists the factors affecting the fabrication cost of dielectric capacitors, such as sintering temperature, raw material costs, and types of internal electrodes, to promote the industrial application of ceramic energy storage capacitors.

A review on the development of lead-free ferroelectric energy-storage ceramics and multilayer capacitors

Ultrahigh piezoelectricity in lead-free piezoceramics by synergistic design

Perovskite-type 0.72BiFeO3-0.28BaTi1-x
 Nb
 x
 O3 (BF-BTNx) ceramics were fabricated via a conventional oxide-mixed method. The phase transition behaviors, composition-dependent grain size, dielectric, ferroelectric and piezoelectric properties were investigated as a function of Nb content. The temperature dependence of dielectric permittivity showed that thermally driven normal to diffuse ferroelectric transition and Nb-doping induced normal to relaxor ferroelectric transition. Simultaneously, the butterfly shape to sprout shape transition for electric-field-induced strain curves and saturation to slim P-E hysteresis loops transition were associated with the normal-to-relaxor transition. And the low hysteresis strain curves for relaxor BF-BTNx ceramics indicated that the system was a promising candidate for high precision actuation applications. In addition, XRD results revealed that Nb-doping induced a structural transition from rhombohedral phase to pseudo-cubic phase, which may be the origin of normal-to-relaxor ferroelectric phase transition.

Normal-to-relaxor ferroelectric phase transition and electrical properties in Nb-modified 0.72BiFeO 3 -0.28BaTiO 3 ceramics

Mn-doped 0.97Bi0.47Na0.47Ba0.06TiO3–0.03K0.5Na0.5NbO3 (BNBT–KNN) lead-free energy storage ceramics were prepared by the conventional solid-state reaction methods. Effects of Mn addition on the microstructures and energy storage properties of the ceramics were investigated. XRD analysis revealed that all the ceramics possessed a single perovskite structure. As the Mn content arose from 0 to 3 mol. %, the average grain size of the BNBT–KNN ceramics increased by nearly 4 times (from ~1.6 to ~6.2 µm). The energy storage density of the BNBT–KNN ceramics firstly increased and then decreased with increment of Mn addition. With the rise of external electric field loaded on the ceramics, the energy storage density increased drastically, and a maximum value of 0.938 J/cm3 at 79 kV/cm was achieved by the BNBT–KNN samples with 1.0 mol. % Mn content.

Microstructures and energy storage properties of Mn-doped 0.97Bi0.47Na0.47Ba0.06TiO3–0.03K0.5Na0.5NbO3 lead-free antiferroelectric ceramics

The structural origin of high piezoelectricity in perovskite-type relaxor ferroelectrics is a fundamental issue that remains elusive for decades. In this study, high and unstable piezoelectricity for the poled ceramics, accompanied with a crossover from a nonergodic relaxor to an ergodic relaxor state at room temperature, has been observed for 0.95(Bi0.5Na0.5)1-x
 (Li0.5Sm0.5)
 x
 TiO3–0.05BaTiO3 ceramics with x = 0.06. The result suggests that the high piezoelectric activity origins from the electric field-induced-ordered nanodomains. The rapid loss of piezoelectricity stems from the reversibility of the ordered nanodomains after removing applied electric field.

Guanghui Rao

Papers

Ultrahigh piezoelectricity in lead-free piezoceramics by synergistic design

Normal-to-relaxor ferroelectric phase transition and electrical properties in Nb-modified 0.72BiFeO 3 -0.28BaTiO 3 ceramics

Microstructures and energy storage properties of Mn-doped 0.97Bi0.47Na0.47Ba0.06TiO3–0.03K0.5Na0.5NbO3 lead-free antiferroelectric ceramics

High piezoelectricity associated with crossover from nonergodicity to ergodicity in modified Bi0.5Na0.5TiO3 relaxor ferroelectrics