Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

In this critical review we consider the large literature that has accumulated in the past 5-10 years concerning solution-mediated crystallisation of complex oxide materials using hydrothermal, or more generally solvothermal, reaction conditions The aim is to show how the synthesis of dense, mixed-metal oxide materials, usually prepared using the high temperatures associated with solid-chemistry, is perfectly feasible from solution in one step reactions, typically at temperatures as low as 200 °C, and that important families of oxide materials have now been reported to crystallise using such synthetic approaches We will focus on two common structures seen in oxide chemistry, ABO(3) perovskites and A(2)B(2)O(6)O' pyrochlores, and include a systematic survey of the variety of chemical elements now included in these two prototypical structure types, from transition metals, in families of materials that include titanates, niobates, manganites and ferrites, to main-group elements in stannates, plumbates and bismuthates The significant advantages of solution-mediated crystallisation are well illustrated by the recent literature: examples are provided of elegant control of crystal form from the nanometre to the micron length scale to give thin films, anisotropic crystal morphologies, or hierarchical structures of materials with properties desirable for many important contemporary applications In addition, new metastable materials have been reported, not stable once high temperatures and pressures are applied and hence not amenable using conventional synthesis We critically discuss the possible control offered by solvothermal synthesis from crystal chemistry to crystal form and how the discovery of new materials may be achieved Computer simulation, combinatorial synthesis approaches and in situ methods to follow crystallisation will be vital in providing the predictability in synthesis that is needed for rational design of new materials (232 references)

Solvothermal synthesis of perovskites and pyrochlores: crystallisation of functional oxides under mild conditions

BiFeO3, the paradigm of single-phase multiferroic materials, has potential applications in information storage, sensors and actuators This perovskite has a rhombohedral R3c crystallographic structure and shows a spin-modulated cycloidal magnetic structure with a modulation period of ∼62 nm It reveals magnetoelectric coupling at room temperature However, its low remanent magnetization and relatively important leakage current are the main limitations for possible applications In this review we summarize recent studies on doped BiFeO3 Special attention is put on obtaining and sintering bulk BiFeO3 ceramics and the effect of doping on the electric and magnetic properties

BiFeO3: A review on synthesis, doping and crystal structure

Studies of nanosized forms of bismuth (Bi)-containing materials have recently expanded from optical, chemical, electronic, and engineering fields towards biomedicine, as a result of their safety, cost-effective fabrication processes, large surface area, high stability, and high versatility in terms of shape, size, and porosity. Bi, as a nontoxic and inexpensive diamagnetic heavy metal, has been used for the fabrication of various nanoparticles (NPs) with unique structural, physicochemical, and compositional features to combine various properties, such as a favourably high X-ray attenuation coefficient and near-infrared (NIR) absorbance, excellent light-to-heat conversion efficiency, and a long circulation half-life. These features have rendered bismuth-containing nanoparticles (BiNPs) with desirable performance for combined cancer therapy, photothermal and radiation therapy (RT), multimodal imaging, theranostics, drug delivery, biosensing, and tissue engineering. Bismuth oxyhalides (BiOx, where X is Cl, Br or I) and bismuth chalcogenides, including bismuth oxide, bismuth sulfide, bismuth selenide, and bismuth telluride, have been heavily investigated for therapeutic purposes. The pharmacokinetics of these BiNPs can be easily improved via the facile modification of their surfaces with biocompatible polymers and proteins, resulting in enhanced colloidal stability, extended blood circulation, and reduced toxicity. Desirable antibacterial effects, bone regeneration potential, and tumor growth suppression under NIR laser radiation are the main biomedical research areas involving BiNPs that have opened up a new paradigm for their future clinical translation. This review emphasizes the synthesis and state-of-the-art progress related to the biomedical applications of BiNPs with different structures, sizes, and compositions. Furthermore, a comprehensive discussion focusing on challenges and future opportunities is presented.

/pdf/the-versatile-biomedical-applications-of-bismuth-based-4weqqirlrh.pdf

The versatile biomedical applications of bismuth-based nanoparticles and composites: therapeutic, diagnostic, biosensing, and regenerative properties

The processes occurring during the early stages of the formation of crystalline solids are not well understood thus preventing the rational synthesis of new solids. The investigation of the structure-forming processes is an enormous challenge for both analytical and theoretical methods because very small particles or aggregates with different chemical composition and different sizes must be probed, both before and during nucleation. Furthermore, these precursors are present in a complex and dynamic equilibrium. This Review gives a survey of the in-situ methods available for the study of the early stages of crystallization of solids and how they can help in the synthesis of metastable polymorphs, of transient intermediates, and/or precursors displaying new or improved properties. Examples of actual research demonstrate the necessity and potentials but also the limitations of in-situ monitoring of the formation of crystalline solids.

In-situ monitoring of the formation of crystalline solids.

Hydrothermal synthesis of perovskite bismuth ferrite crystallites

Lead zirconate titanate thin films prepared on metal substrates by the sol–gel methods

The effect of LaNiO3 buffer layer thickness on the electric properties of Pb(Zr0.53Ti0.47)O3 thin films deposited on titanium foils

Polycrystalline lead zirconate titanate (PZT) thin films were synthesized on titanium substrates at a processing temperature of 160degC for 16 hours by using a hydrothermal method. The effects of KOH concentration on the phase evolution and morphology of the films were investigated. The as-synthesized PZT thin films using KOH concentration of 4 mol/1 have a dielectric constant and loss of 515 and 0.35 at 103 Hz respectively. The dielectric loss, tandelta and leakage current of hydrothermal PZT thin films were reduced by additional annealing at 100-400degC in air. Moreover, the annealed hydrothermal PZT thin films exhibit typical ferroelectric hysteresis loops at room temperature.

Electrical Properties of Lead Zirconate Titanate Thin Films by a Hydrothermal Method

Lead Zirconate Titanate (PZT) powders have been synthesized by a hydrothermal method at the processing temperatures of 120–220 oC for 1.5–50 hours, based on the reaction of Pb(CH3COOH)2•3H2O, ZrOCl2•8H2O, Ti(C4H9O)4 and KOH. Hydrothermally treated PZT powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation infrared (FTIR) techniques respectively. The influences of hydrothermal synthesize conditions on the crystalline structure and the morphology of PZT particles were investigated. Crystallized PZT powders could be synthesized at the KOH concentration of >2.5 mol/l.

Lingjuan Che

Papers

Hydrothermal synthesis of perovskite bismuth ferrite crystallites

Lead zirconate titanate thin films prepared on metal substrates by the sol–gel methods

The effect of LaNiO3 buffer layer thickness on the electric properties of Pb(Zr0.53Ti0.47)O3 thin films deposited on titanium foils

Electrical Properties of Lead Zirconate Titanate Thin Films by a Hydrothermal Method

Characterization of Lead Zirconate Titanate Powders Prepared by a Hydrothermal Method