Defect chemistry and charge transport properties of mixed bismuth oxides with layer lattices

The year of 2021 is the 100th anniversary of the first publication of ferroelectric behaviour in Rochelle salt, focussing on its piezoelectric properties. Over the past many decades, people witnessed a great impact of ferroelectricity on our everyday life, where numerous ferroelectric materials have been designed and developed to enable the advancement of diverse applications. Now the driving forces for ferroelectric studies stem from regulations on environment, human health and sustainable society development. This leads to the resurgence of lead-free ferroelectric materials for the expectation of replacing the state-of-the-art lead-based counterparts. The next wave of explorations into ferroelectric materials maybe related to the Internet-of-Things, which requires millions of self-powered sensors and memories. This will promote research on ferroelectrics for sensing, energy harvesting and storage, communication and non-volatile memories, from centimetre scale to micro and nanoscale. This review gives a brief discussion from the materials viewpoint, on the challenges and current status of lead-free ferroelectrics based on prospective applications.

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Lead-free ferroelectric materials: Prospective applications

Electrical properties and Curie temperature of Li/Ce co-doped BaBi4Ti4O15–Bi4Ti3O12 intergrowth ceramics

Bismuth layer-structured ferroelectric Bi3R2Ti3FeO15 (R = Bi, Nd, and Gd) ceramics were synthesized by conventional solid-state reaction. All the samples showed an orthorhombic structure with A21am space group. Bi3Nd2Ti3FeO15 and Bi3Gd2Ti3FeO15 presented a reduction in the orthorhombicity when compared to Bi5Ti3FeO15. The magnetic susceptibility of all samples followed the Curie–Weiss law, with negative values of the Curie–Weiss temperature, demonstrating that the magnetic interactions are antiferromagnetic in nature. The magnetization curves suggested a weak canted antiferromagnetic behavior for temperatures below 25 K, followed by a linear behavior in the curves at high temperatures. Mossbauer spectroscopy measurements revealed an increase of the quadrupole splitting values as the temperature decreases, indicating that the samples present local distortions, favoring the existence of weak ferromagnetic phase via the antisymmetric Dzyaloshinskii–Moriya interaction.

Effects of the Bi 3+ substitution on the structural, vibrational, and magnetic properties of bismuth layer-structured ferroelectrics

Effect of tantalum substitution on the structural and electrical properties of BaBi8Ti7O27 intergrowth ceramics

Effects of phase structure on up-conversion photoluminescence and dielectric performance in Er3+ doped (Bi0. 5Na0. 5)TiO3-BaTiO3 lead-free ceramics

Solid solution 0.94Na0.5Bi0.5TiO3–6BaTiO3 (NBT–6BT) is considered to be one kind of lead‐free piezoelectric materials with excellent electrical properties due to the existence of morphotropic phase boundary (MPB). However, its relatively lower depolarization temperature is a long‐standing bottleneck for the application of NBT‐based piezoelectric ceramics. In this work, the influence of thermal quenching on depolarization temperature and electrical properties of rare‐earth Ho‐doped NBT–6BT lead‐free ceramics was investigated. It was shown that the relative high piezoelectric performance, as well as an improvement of depolarization temperature (Td), can be realized by thermal quenching. The results showed that the quenching process induced high concentration of oxygen vacancy, giving rise to the change of octahedra mode and enhanced lattice distortion, which is benefit to the temperature stability of piezoelectric and ferroelectric properties. Furthermore, up‐conversion photoluminescence (PL) of Ho‐doped NBT–6BT could be effectively tuned by the introduction of oxygen vacancy, suggesting a promising potential in optical–electrical multifunctional devices.

https://link.springer.com/content/pdf/10.1557/s43578-020-00076-3.pdf

Laiqi Zheng

Papers

Effect of tantalum substitution on the structural and electrical properties of BaBi8Ti7O27 intergrowth ceramics

Effects of phase structure on up-conversion photoluminescence and dielectric performance in Er3+ doped (Bi0. 5Na0. 5)TiO3-BaTiO3 lead-free ceramics

Effects of defect on thermal stability and photoluminescence in quenched Ho‐doped 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 lead‐free ceramics