Investigations on the structural chemical and thermodynamical analysis of nanostructured multiferroic bismuth ferrite and lithium manganese phosphate

Abstract

BiFeO3 (BFO) is a multiferroic material which exhibits roomtemperature ferroelectric (ferroelectric phase transitition TC at 830 °C) and antiferromagnetic (Neel temperature TN at 370 °C) properties simultaneously. For the same reasons, BFO have been reported for its ferroelectric and magnetic nature in various forms such as single crystals, thin films and in ceramic forms such as multicrystalline and in nanocrystalline forms. The achievement of single phase and understanding of electric and magnetic nature have paved the way for materials scientist to look after various methods in achieving the same. For the past three decades, lithium-ion batteries have been the most promising materials used in rechargeable batteries for conversion of chemical to electrical energy which is primarily used as secondary sources in electronic devices for supply of power in devices such as laptops, computers, camera and cellular phones etc. The commercialization of LIBs in early 90 s has opened up new areas of research in developing a lithium based material for cathodic applications. The insertion of lithium ions into the transition metal oxide has gained much importance due to the light weight nature of lithium and also higher discharge phenomena that occurs plateau region. Among these the olivine based lithium metal phosphate has gained much importance due to their environmental friendly constituent, low energy density and primarily due to their lower cost effectiveness has created much interest towards the stable phase analysis of lithium metal phosphates of LiMPO4 (M = Co, Fe, Ni, Na, etc.,The literature survey on ABO3 structure and the importance of perovskite structure is discussed in detail. A brief literature about the multiferroic structural details, physical and chemical inertness of bismuth ferrite (BiFeO3) and lithium manganese phosphate (LiMnPO4) compounds are discussed in detail. The detailed literature on olivine structure LiMnPO4 is elaborated for its numerous applications as cathodic materials in lithium battery applications. The main objective of the present thesis is to synthesis the single phase materials of Bismuth ferrite (BiFeO3) and Lithium manganese phosphate (LiMnPO4) for its application in lithium ion batteries (LIB) as cathodic material. There were several reports on the synthesis of LiMnPO4 by various methods, whereas we have adopted an indigenously build autoclave is used in the experimental purposes. The possible use of multiferroic BiFeO3 in combination with LMP can be attempted for LIB application for which the requirement of BFO in single phase is an important criteria. Keeping in view the objective was focused to obtain single phase BFO by the use of various binding agents possessing 2, 3 and 4 carboxylic groups. Bismuth ferrite (BiFeO3) in the nanocrystalline form was synthesized by self-combustion method by the use of various fuels such as citric acid, EDTA and DL-malic acid in 1:1 metal ratio. The binding agents due to the presence of different functional groups which tends to help the crystallization of bismuth ferrite into crystalline form from the amorphous gel form. Single phase BFO (BiFeO3) could be obtained when DL-malic acid is used as binding agent and that the compounds crystallizes into stable phase above 450 oC. The phase transition to orthorhombic could be observed for BFO at around 450 oC and the literature reports were reported the decomposition of the compounds occurs beyond 827 oC. The decomposition of the compounds of synthesized BFO occurs above 824 oC for all the fuels newline