Bismuth FerriteThe potential of future electronic memory devices are at its twilight of booming into a new set of generation of memory chips. Instead of having the memory devices of which are as big as tens of nanometer, which is what our today technologys advanced system offers, comes a memory device shrinking to one or two nanometer. If only one can synthesize a way to gasp into his hands the controls of how to separate those regions that have different electric, magnetic and other properties this would be possible.Bismuth ferrite is a compound of bismuth, iron and oxygenBiFeO3. This compound was discovered to have domain walls never been seen by scientists of the department of energy at Lawrence Berkeley National Laboratory of the University of California. Even though Bismuth ferrite was originally know as an insulator, this compound was discovered to have different electrical polarity that conducts electricity at room temperature. In this review, I will focus primarily on the synthesis, physical and chemical properties, industry use and its effect upon disposal to the environment of Bismuth Ferrite.

Chemical and physical propertiesBismuth ferrite, being an inorganic chemical compound, has perovskite structure ( in which planes of heavy atoms, bismuth for this compound, and oxygen alternates with planes of lighter atoms, Iron for this compound, and oxygen atoms) and is said to be one of the most promising multiferroic materials that exhibits multiferroic properties at room temperature. At room temperature, BiFeO3 is classified as rhombohedral that belongs to group R3c. It is synthesize in thin film and in bulk and it temperaturesantiferrmagnetic Neel and ferroelectric Curieare well above room temperature (653 K nd 1100 K, respectively). Its polarization occurs with a magnitude of 90-95 C/cm2 along the pseudocubic 111 direction. Its walls are oriented along two different crystallographic planes, meaning it can be separated with 109-degree, 71-degree, or 180-degree differences in the direction of the polarization. Bismuth ferrite films contains ferroelectric sphere that is between 5 to 10 micrometers. It exhibits week magnetism at room temperature because of the spiral magnetic spin cycloid with a periodicity of 62 nm.

Synthesis/preparation of Bismuth ferriteIn synthesizing this promising alloy, many ways were developed. The following are just some of the ways on how to produce Bismuth ferrite:SOL-GEL TECHNIQUEA 2:1 ratio of bismuth and iron was prepared from the starting materials bismuth nitrate and ferric chloride. The excess bismuth is used to compensate the bismuth evaporated during high temperature annealing. Bismuth nitrate and ferric chloride were dissolved in acetic acid and was added with ethylene glycol that served as a drying control agent to restrict cracking of the thin films before coat spinning. The solution was them refluxed for 5 hour. Figure 1. Flow chart of the synthesis of BiFeO3 .

Figure 1The precursor was coated on copper substrate at 3000 rpm for 30 seconds while spinning after it was cooled down to room temperature. For thicker film, the process was repeated. After the process, the film was kept exposed for 1 hour for gel film to form via hydrolysis and polymerization. The film was dried via heat treatment at a temperature of 300o C for 2 hours. The Crystallization, densification and microstructure of the films were then examined.SUPERFACTANT ASSISTED AUTOCOMBUSTION SYNTHESIS

Figure 2Bismuth ferrite powder was synthesized by a solution evaporation route. A 0.25 M Bi(NO3)3 and a 0.25 M Fe(NO3)3 was prepared by dissolving it in dilute nitric acid. The two solutions were mixed in a beaker. A 0.1 mole ratio of glycine was added to the solution above with respect to nitrate. The supernatants Triton X, and ALS (ammonium lauryl sulfate) were added to the solution with a mole ratio of 0.05 with respect to the metals. The solution was then heated on a hot plate with continuous stirring until it reaches its boiling temperature such time that all liquid have already evaporated. A brown fume that evolves during the process was obtained at the bottom of the beaker. The powder was than calcined at 500oC and 550oC. the crystalline size of the powder was then computed using the Scherrer formula.Figure 2. Flow chart of supernatant assisted autocombustion synthesis.SUPER CRITICAL HYDROTHERMAL SYNTHESISThe equal mole amount (0.003 mol) of Bi(NO3)35H2O and Fe(NO3)3.9H2O was weighted. Then, Bi(NO3)3.5H2O and Fe(NO3)3.9H2O was dissolved in 250 ml deionized water and was heated until homogenized. It was than transferred to a reactor vessel. A stainless steel 316 with 180 mL volume bath type reactor was used and was heated using an electrical heater.The hydrothermal reaction was performed in the reactor vessel at 500o C for 2 hours. After then, the reactor vessel was reduced to stop the reaction with cold water so that the product will be collected through washing the reactor with deionized water and cetrifugate to remove the reagent that didnt reacted. Then the BiFeO nanoparticles were dreid at 40o C for 24 hours.The identity of the synthesized nanoparticled was then X-rayed for diffraction measurements. The size and the shape of the obtained nanoparticled was then studied using transmission electron microscopy.

CO-PRECIPITATE/ HYDROTHERMAL SYNTHESISThe starting materials were 0.227 g of FeCl3* 6H2O and 0.407 g Bi(NO3)3* 5H2O. These were dissolved in ethandiol of 20 mL of with stirring for 2 hrs. for fine precipitation, Fe/Bi solution was dissolved slowly and was dripped into diluted ammonia solution (0.3 mol/L) with stirring for 30 minutes. A precipitate will then be observed. This precipitate was then washed with de-ionized water for 5-6 times, and underwent a hydrothermal reaction using NaOH as mineralizer. The hydrothermal was performed with various reaction temperatures ranging from 140o-220o and with varied NaOH concentrations of 0.05-0.25 mol/L for 12 hrs. The autoclave was then cooled naturally to room temperature after the hydrothermal reaction. The products were then washed with de-ionized water until it was neutral.The phase structure of as-prepared BiFeO3 powders then subjected to characterization by X-ray diffraction (XRD), Rigaku D/max220PC) with graphite monochromatozed CuK radiation, the scan rate was 10o/min. SEM (Dutch Quanta 200) was employed to determine particle morphology and size. Differential scanning calorimetry (DSC, SDT 2960) of BiFeO3 powders was then carried out from room temperature to 1100oC in nitrogen ambient at a scan rate of 10oC/min.MORPHOLOGY-CONTROLLED HYDROTHERMAL SYNTHESIS USING VARIOUS ALKALINE MINERALIZERSThe chemical reagents used were bismuth nitrate [Bi(NO3)35H2O], iron chloride (FeCl36H2O), potassium hydroxide (KOH), sodium hydroxide (NaOH) and lithium hydroxide (LiOH). The equal molar amount (0.02 M) of Bi(NO3)35H2O and FeCl36H2O were carefully weighted. To beaker 1, Bi(NO3)3*5H2O was liquefied in 10 ml ethylene glycol with continuous stirring and to beaker 2, FeCl36H2O was dissolved in 10 ml distilled water. Then, the solution in beaker 2 was slowly added into the solution in beaker 1 stirring for 15 min. To adjust its pH to or greater than 10, 13.2 M solution of ammonia was slowly dropped into the homogenous solution with constant stirring, and a brown-colored precipitate will be formed. To remove NO3- and Cl- ions from the precipitate, it was filtered and repeatedly was washed with distilled water. The suspension was then transferred into a 40 ml Teflon-lined stainless steel autoclave and to fill the capacity of 70%, mineralizer solutions was added. Potassium hydroxide (KOH), lithium hydroxide (LiOH) and sodium hydroxide (NaOH) were utilized for the preparation of mineralizer solutions. The hydrothermal was performed with a reaction temperature of 180o C with varied concentratios of the mineralizer (0.02-0.15 M) for 16 hours with autogeneous pressure. The final products of the autoclave were filtered out and were washed with distilled water and absolute ethanol several times to remove residual soluble salts and unreacted ions after the autoclave was cooled down naturally to room temperature. The obtained powders were dried at 80C for 5 hours before characterization.The phase structure of the as-synthesized BiFeO3powders was characterized by X-ray powder diffraction with monochromated CuK radiation ( = 1.5406 ) at 40 Kv and 50 Ma. The transmission electron microscope (TEM), high-resolution transmission electron microscope (HR-TEM) and selected area electron diffraction (SAED) images of the final products were then observed using a JEOL 200 CX TEM with acceleration voltage of 300 Kv.Important use in the industryIn the past studies, bismuth ferrite has proven itself for its effective and applications to the industry. Bismuth ferrite was used as high tech magnetic tapes, used for its superconductivity, used in environmental engineering; and finally, is used to enhance spontaneous magnetization. But for this review, I will focus on the new discovered application of bismuth ferrite--nanoscale shape-memory oxide.Bismuth ferrite is a compound of bismuth, iron and oxygen. This multiferroic compound has been studied thoroughly in recent years by many scientists. As bismuth ferrite, being a multiferroic alloy, displays both ferromagnetic and ferroelectric properties, meaning it responds to applications of magnetic field or external electric. In this latest study by the scientists of the University of California in Berkley they were able to introduce an elastic-like phase transition into bismuth ferrite by means of electric field.Bismuth ferrite's application to the electric field allowed them to develop a phase transformation to be achieve that is reversible even without assistance of an external stress recovery said Ramesh of the University of California in Berkley. This new discovery of the shape-memory alloys claimed to be the champion for elasticity and is primed to take over the shape memory apps to a whole new level---which is shrinking it to nanoscale. Researchers in Berkley laboratory have discovered a way to introduce recoverable strain into bismuth ferrite up to 14%. This is larger than any shape-memory effect observed in any metals for now. This discovery opens new door to for the application of many fields such as that in medical, energy, and specially electronics. According to Jinxing Zhang this bismuth ferrite they newly developed displays amazing features including being stable even when reduced to nanometer compared to other shape-memory alloys. One more feature is that its responses are fast due the electrical field needed to activate shape-memory alloy rather than the primitive way of using thermal fields.A shape-memory effect is when a solid material grows back to its original shape after being deformed after stress is applied is an ability of a metal to be elastic. In the past, this has always been involved with heating. Nickel-titanium or "nitinol alloy is a shape-memory alloy that has a great use to those that are in the field of medicine. It is used intents for angioplasty and in medical joints. This memory effect of alloy has also have a great impact for non-medical fields. An example is the actuators in smart materials and in Microelectro-Mechanical Systems (MEMS). But as scientist try to achieve nano-scale size of this shape-memory alloys, various problems and instabilities arises such as micro-cracking and oxidation. But with the new study on bismuth ferrite, scientists of Berkley Lab's materials Sciences Division of the University of California in Berkley were able to eliminate surface issues and were able to integrate it with microelectronics by achieving shape-memory effect to an oxide material rather than in alloy metals. According to Zhang, this bismuth ferrite they developed has "ultra-high work function density during actuation that is almost two orders of magnitude higher than what a metal alloy can generate." Ramesh also added that even though aspects like hysteresis, micro-cracking and so many more needs to be accounted when it will be applied to real devices, the discovery of bismuth ferrite being able to show large shape-memory effect only shows that it is not an ordinary material. This alloy has great potentials that it can be use in the future in nanoelectromechanical devices and other state-of-the-art nanosystems.Environmental threatThe treat that it impose to the environment is due to the use of lead. Bismuth ferrite is a piezoelectric material that is a lead-based perovskite compound. Lead that is used poses threats to neurotoxin that may seriously affect human health, especially the young ones and to the environment. But because of the threat it poses researchers of University of California in Berkley together with the U.S. Department of Energys Lawrence Berkeley national laboratory (Berkely Lab) have discovered a way to produce a lead-free alternative to the current crop of piezoelectric material by applying compression to the thin films of bismuth ferrite. However, the by this method bismuth ferrite crystal have the tendency to revert back to its original rhombohedral-like phase but by alternating the material from squeezing and relaxing, the researchers was able to shuffle the material back and forth between the two phases.Indeed alloys have shaped the world of technology and technology shaped the world of alloys as well. Because of the pursuit to better living, continuous discovery of alloys application has already been rampant and have been beneficial to human race.

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Physicists observe new magnetic state of bismuth ferrite (n.d.). In Phys.org. Retrieved December 20, 2013, from http://phys.org/news/2013-05-physicists-magnetic-state-bismuth-ferrite.html#inlRlv

Bismuth Ferrite (BiFe03) from READE (n.d.). In READE. Retrieved December 24, 2013, from http://www.reade.com/component/content/article/10445-bismuth-ferrite-bife03-bfo-multiferroic-bismuth-ferrite-powder-bismuth-ferrite-sputtering-targets-bismuth-ferrite-nanotubes-bismuth-ferrite-nanowires-bismuth-ferrite-nanocrystals-superconductivity-spontan?q=bismuth+ferriteBismuth Ferrite (n.d.). In American Elements. Retrieved December 23, 2013, from http://www.americanelements.com/biferr.htmlPhysicists Observe New Magnetic State of Bismuth Ferrite (n.d.). In Technology.org. Retrieved December 20, 2013, from http://www.technology.org/2013/05/02/physicists-observe-new-magnetic-state-of-bismuth-ferrite/Remembrances of Things Past: Berkeley Lab Researchers Discover Nanoscale Shape-Memory Oxide (n.d.). In Hispanicbusiness. Retrieved December 20, 2013, from http://www.hispanicbusiness.com/2013/12/3/remembrances_of_things_past_berkeley_lab.htmResearchers take the lead out of piezoelectrics (n.d.). In Phys.org. Retrieved December 20, 2013, from http://phys.org/news177340310.htmlHu, Y., Fei, L., Zhang, Y., Yuan, J., Wang, Y., and Gu, H., (2010). Synthesis of Bismuth Ferrite Nanoparticles via a Wet Chemical Route at Low Temperature. Hindawi Publishing Incorporated, 2011(2011), 6 pages. Retrieved from http://www.hindawi.com/journals/jnm/2011/797639/Haneberg, D. H. (2011). A Finite-Size Study on Samarium-Substituted Bismuth Ferrite: Multiferroic and Lead-Free Piezoelectric Materials. Abstract retrieved from NTNU.Shurygina V.Yu., Zhereb V.P., Skorikov V.M. (2013). MECHANISM OF SOLID STATE SYNTHESIS OF BISMUTH FERRITE BI25FEO39. Abstract from Digital scientific journalPDF:Synthesis and characterization of bismuth and its component (2009) by Vishwambar Nath ShuklaBismuth ferrite nanoparticles formation via a supercritical hydrothermal synthesis method (2012) by J. Karimi, A., and Golzary, CSynthesis and Properties of Bismuth Ferrite Multiferroic Nanoflowers (2000s) by Chybczynska, K., awniczak, P., Hilczer, B., eska, B., Pankiewicz, R., Pietraszko, A., Kepinski, L., Kauski, T., Cieluch, P., Matelski F., and Andrzejewski, B.