**4.1 Ferroelectric**

Ferroelectricity electricity is usually expected to disappear in smaller sizes due to a decrease in the relative length of the dipoles [66, 67]. Exact measurement of ferroelectricity in 0-D nanostructures and identification of proper ferroelectric size - the result is a difficult task. To begin with, making electronic contact with a single nanoparticle can only be done using scanning test methods, and no report has ever published the ferroelectric hysteresis characteristics of a single nanoparticle according to our knowledge. The problem is exacerbated by the small size and leaky nature of BFO nanoparticles due to the reduced bandgap and switching voltages that are likely to be very close to the dielectric cracking [46]. Vasudevan et al. [57] investigated the ferroelectric characterization of BFO nanoparticle clusters prepared for automatic firing methods using band excitation piezoresponse spectroscopy (BEPS) and piezoresponse force microscopy (PFM) (larger than 50 nm). They confirmed the ferroelectricity of nanoparticles by obtaining a symmetric piezoresponse loop with a compliant 8 V voltage of a single batch distributed in the LSMO/ STO substrate (**Figure 3 (a)**). In addition, they found the properties of the ferroelectric domain (**Figure 3 (b)** and **(c)** within groups of particles, similar to those found in small BFO films [61]. There is often a direct link between ferroelectricity and lattice strain (using a known strain-polarization coupling). This means that a detailed structural investigation into each area's lattice parameter or removal can

*Synthesis and Characterization of NanoBismuth Ferrites Ceramics DOI: http://dx.doi.org/10.5772/intechopen.104777*

#### **Figure 3.**

*(a) Piezoresponseand phase hysteresis loops of a solitary BiFeO3 nanoparticle. Out-of-plane PFM amplitude (b) and phase (c) pictures of a nanoparticle cluster, pre, and post-putting on +10 V, 5 s pulse towards the center of this cluster. Insets in (b) and (c) demonstrate the PFM amplitude and phase pre applying the bias; correspondingly, the above assessment had been performed.*

provide important information. Selbach et al. [31] A systematic study of the relationship between nanoparticle size and BFO lattice parameter illustrates this point. As shown in **Figure 3**, these researchers found that nanoparticles more prominent than 30 nm have lattice limits than a BFO mass. In contrast, at less than 30 nm, the lattice parameter of BFO nanoparticles extends from the mass and approaches the cubic (i.e., paraelectric) perovskite structure. There is a decrease in the rhombohedral deviation of the cell unit (i.e., a decrease in c/a). When the rhombohedral angle reaches 60o, it equals the unit, indicating a fine cubic perovskite [31]. A significant dc size of 9 1 nm of ferroelectricity was obtained using the empirical model to match tetragonality based on BFO size [31]. Automatic polarization determined by removing Bi3+ and Fe3+ cations at 13 nm nanoparticles was 75% of the total volume. This makes BFO nanoparticles an exciting class for many materials because they can have both a strong magnetic field (discussed below) and sufficient ferroelectric polarization for novel applications [31].

## **4.2 Photocatalytic**

Compared to BFO thin films, which typically have a bandgap of 2.7 eV [22], BFO nanoparticles prepared chemically have a bandgap as low as 1.8–2.3 eV. As a result, they are appealing for use in photocatalysis. Nanosized BFO particles have demonstrated improved photocatalytic performance, which can be applied to the degradation of organic pollutants such as dye compounds of Methyl orange (MO), Methylene Blue (MB), Congo Red (CR), or Rhodamine B. (RhB). Geo et al. [22], for example,

confirmed that BFO nanoparticles, in addition to responding to UV light, have excellent MO degradation ability when exposed to visible light (**Figure 4(a)**).As shown in **Figure 4(b)**, Geo et al. discovered that Gd-doped BFO nanoparticles could improve their photocatalytic properties by increasing RhB degradation rates from 79 percent for BFO to 94 percent Bi0.9Gd0.1FeO3 [26]. Using BFO as a photocatalytic agent is its photostability, affecting photocatalytic efficiency under visible light. It is investigated the nonphotostability of BFO nanoparticles by studying RhB dye decolorization at pH 2, 4, and 6, 7, as shown in **Figure 4(c)**. They discovered that photo corrosion occurs in the RhB dye solution due to the dissolution of Fe from the Fe-O bond, resulting in nonphoto stability. This photo corrosion can be explained as an offshoot of the BFO band offset concerning the RhB dye, in which holes can be injected from the RhB dye into the BFO valence band. As shown in **Figure 4**, replacing the BFO nanoparticles in the RhB solution at regular intervals can achieve a much higher decolorization rate, which can even exceed TiO2 (d). As a result, BFO nanoparticles are extremely promising for visible-light-driven photochemistry. Compared to small BFO films, typically with a 2.7 eV bandgap [22], BFO nanoparticles are chemically modified with a band as low as 1.8–2.3 eV [22, 54]. As a result, they requested use in photocatalysis. Nanosized BFO particles have shown improved photocatalytic activity, which can be used in the decomposition of organic pollutants such as compounds of Methyl orange (MO), Methylene Blue (MB), Congo Red (CR), or Rhodamine B (RhB).

### **Figure 4.**

*(a) Photocatalytic removal activities of methyl orange under UV-vis light irradiation and visible light irradiationutilizingBiFeO3 nanoparticles as well as bulk, [51] recreated with authorization from ref 104, copyright2007 WILEY-VCH Verlag GmbH & Co. kraal, Weinheim; (b) photocatalytic removal effectiveness of RhButilizingGd substituted BFO nanoparticle samples, [26] recreated with authorization from ref 26, copyright 2010 American Chemical Society (c) and (d) photo removal information of RhB utilizingBiFeO3 as photo reagent at different pH values under AM1.5 lighting; [65] (d)tests had been carried outwith the substitution of theBFO nanopowders at frequentperiods, into the dye answer, decolorization at pH = 2 reveals higher than 95% decolorization after 10 min, the inset demonstratesthe removal activities of RhB utilizingnanostructured (Degussa P25) TiO2, [65] recreated with authorization from ref 103, copyright 2012 Royal Society of Chemistry.*
