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

The temperature-dependent electrical properties of Bi0.5Na0.5TiO3–BaTiO3–Bi0.5K0.5TiO3 near the morphotropic phase boundary

Preparation technique and characterization method are critical aspects to a functional material. The preparation techniques strongly affect the electrical properties of a material. In this chapter, we pay much attention to several preparation techniques of lead-free piezoelectric materials including ceramic, nanostructure, thin film and single crystal. The influences of different preparation techniques on electrical properties and microstructure of a material are also addressed. In addition, various characterization methods on crystal structure, domain structure and electrical properties are also introduced.

Preparation and Characterization

The multisite occupation of Li+ cations in perovskite structure of (Bi1/2Na1/2)TiO3-based solid solution is investigated, which is rarely reported in previous studies. The multisite occupation in relation to the Li2CO3 doping level has been demonstrated with the aid of the microstructure and temperature-dependent conductivity analysis: As the addition of Li2CO3 is below 0.75 mol. %, the introduced Li+ cations precede to enter the A sites of the perovskite lattice to compensate for the A-site deficiency stemming from the high-temperature sintering process. Once the addition exceeds 0.75 mol. %, the excess Li+ cations will occupy B sites to substitute for Ti4+ and give rise to the generation of oxygen vacancies. The proposed multisite occupation behavior of Li+ cations and its derivative effects, involving the clamping effect or grain size effect, have made the piezo-/ferroelectric performances of the 0.85BNT–0.10BKT–0.05BT ceramics optimized at the Li2CO3 addition of 1.0 mol.%:d33 = 163 pC/N, Pr = 40.9 μC/cm2.

Effect of lattice occupation behavior of Li+ cations on microstructure and electrical properties of (Bi1/2Na1/2)TiO3-based lead-free piezoceramics

BiFeO3 thin films free of secondary phases were obtained by the soft chemical solution on Pt(111)∕Ti∕SiO2∕Si substrates after annealing at 500°C for 2h. The film grown in the (100) direction presented a remanent polarization Pr of 31μC∕cm2 at room temperature. Electrical measurements using both quasistatic hysteresis and pulsed polarization confirm the existence of ferroelectricity with a switched polarization of 60–70μC∕cm2, ΔP=(P*−P). Low leakage conduction and an out-of-plane piezoelectric (d3) coefficient of 40pm∕V were obtained by the improvement of preparation technology.

Kyu Sang Choi

Papers

Enhanced piezoelectric performance of donor La3+-doped BiFeO3–BaTiO3 lead-free piezoceramics

Dielectric and piezoelectric properties of Li-substituted lead-free (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3-BaTiO3 ceramics

Lead-free piezoelectric BiFeO3-BaTiO3 thin film with high Curie temperature

Landau-Khalatnikov simulation for magnetoelectric coupling in CoFe2O4–BaTiO3 composites

Mechanical Spring Discharge-Based Multipillar Triboelectric Nanogenerator with Enhanced Power Output