Multiferroic ceramics of (0.70−x)BiFeO3–0.30BaTiO3–xBi(Zn0.5Ti0.5)O3 + 1 mol% MnO2 with perovskite structure were prepared by a conventional ceramic technique and the effects of Bi(Zn0.5Ti0.5)O3 doping and sintering temperature on the microstructure, multiferroic and piezoelectric properties of the ceramics were studied. All the ceramics possess a pure perovskite structure and no second phases can be detected. After the addition of a small amount of Bi(Zn0.5Ti0.5)O3 (x ≤ 0.05), the ferroelectric and piezoelectric properties of the ceramics are improved and the grain growth is promoted. However, excess Bi(Zn0.5Ti0.5)O3 (x ≥ 0.10) retards the grain growth, degrades the ferroelectricity and piezoelectricity, and induces two dielectric anomalies at high temperature. The ceramics can be well sintered at the very wide range of low sintering temperatures (880–980 °C) and exhibit good densification (relative density: 96.2–98.4 %) and strong electric insulation. The increase in the sintering temperature promotes the grain growth and improves the ferroelectricity of the ceramics. The ceramic with x = 0.05 sintered at 880–980 °C possesses improved ferroelectric and piezoelectric properties with remanent polarizations P
 r of 21.9–28.1 μm/cm2, piezoelectric constants d
 33 of 125–139 pC/N and planar electromechanical coupling factors k
 p of 30.1–32.4 %, and high Curie temperatures T
 C of 523–565 °C. A weak ferromagnetism with remanent magnetizations M
 r of 0.0411–0.0422 emu/g and coercive fields H
 c of 1.70–1.99 kOe were observed in the ceramics with x = 0–0.025.

Structure, Ferroelectric, Piezoelectric, and Ferromagnetic Properties of BiFeO3‐BaTiO3‐Bi0.5Na0.5TiO3 Lead‐Free Multiferroic Ceramics

Donor-doped lead-free Bi0.7Ba0.3(Fe0.7Ti0.3)1−x
 Nb0.66x
 O3 + 1 mol% MnO2 ceramics were prepared by a conventional oxide-mixed method and the effects of Nb-doping on microstructure, piezoelectric and ferroelectric properties of the ceramics were investigated. All the ceramics exhibit a pure perovskite structure with rhombohedral symmetry. The grain growth of the ceramics is inhibited after the addition of Nb doping. High electric insulation (R = 109–1010 Ω⋅cm) and the poor piezoelectric performance and weak ferroelectricity are observed after the addition of Nb2O5 in the ceramics. Different from the donor effect of Pb-based perovskite ceramics, the introduction of Nb into 0.7BiFeO3–0.3BaTiO3 degrades the piezoelectricity and ferroelectricity of the ceramics. The Bi0.7Ba0.3(Fe0.7Ti0.3)1−x
 Nb0.66x
 O3 + 1 mol% MnO2 ceramic with x = 0 exhibits the optimum piezoelectric properties with d
 33 = 133 pN C−1 and k
 p = 0.29 and high Curie temperature (TC = 603∘C).

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Effects of Nb doping on the microstructure, ferroelectric and piezoelectric properties of 0.7BiFeO3–0.3BaTiO3 lead-free ceramics

Nano-structure ferromagnetic-ferroelectric composite materials produced by the sol gel method have great attention in different applications due to their desired properties and applications. Potassium Barium titanate doped with different concentrations of Ni2+ nanoparticles (K0.1Ba0.9Ti(1-x)NixO3; x = 0.0-0.3) were prepared by sol-gel process. The final nanoparticles were obtained through drying and calcination at 200 oC and 600 oC, respectively. The crystalline, nanoparticles' nature and the optical characteristics of the Ni-KBTO nanoparticles are investigated using XRD, SEM, TEM, and optical properties. The XRD and TEM results demonstrate that the Ni2+ NPs were superlatively incorporated within the semi-crystalline KBTO structure. TGA thermogram of all samples shows two weight loss events. The first event is assigned for impurities and/or adsorbed water releasing. The second event was at a higher temperature and assigned as degradation of the nanoparticles. The thermal stability was enhanced by Ni2+ incorporation. The KBTO nanoparticles exhibit enhancement optical bandgap, which decreases from 3 eV to 2.3 eV with increasing Ni2+ in KBTO NPs. This can be ascribed to the change in nanoparticles arrangement and resembles band structures between Ti4+ and Ni2+, resulting in the efficient transfer of charge carriers. The dielectric constant was in the range 106 to 107 at low frequency and about 101 to 102 at high frequency. The Curie temperature of pure Potassium barium titanate is 373 K and 328 K for Potassium barium titanate doped with 20% of Ni2+.

Ni2+ doping effect on potassium barium titanate nanoparticles: enhancement optical and dielectric properties

In the original publication of the article, there are some mistakes regarding the sequence of references. Some references are mislocated. Here is the new version of the full paper.

/pdf/a-collection-of-505-papers-on-false-or-unconfirmed-1g5oczcfbn.pdf

A collection of 505 papers on false or unconfirmed ferroelectric properties in single crystals, ceramics and polymers

Abstract Barium titanate (BaTiO3) has been recognized as an important perovskite ceramic since its discovery due to its excellent dielectric, ferroelectric and piezoelectric properties. Its modifications have been studied in many perspectives depending on applications. In this review, the basic principles of BaTiO3 were described, then followed by the explanation on the recent modifications of BaTiO3 to improve the dielectric properties. Relaxor ferroelectric behavior of BaTiO3 was revealed by combining BaTiO3 with other Bi-based perovskites. These modified- BaTiO3 opened the opportunities for emerging energy storage applications. Next, the modifications for ferroelectric and ferromagnetic aspects were further discussed. BaTiO3 can also be doped by other ions to enhance such properties. Solid solution between Bi-based perovskites such as BiFeO3, (Bi0.5K0.5)TiO3, or Bi(Zn0.5Ti0.5)O3 and BaTiO3 can also improve ferroelectric and ferromagnetic properties. Therefore, these details of recent BaTiO3 modifications may provide guidance for the next BaTiO3 investigations in order to gain the maximum benefits from BaTiO3.

Parichart Aommongkol

Papers

Investigation on ferromagnetic and ferroelectric properties of (La, K)-doped BiFeO3–BaTiO3 solid solution