Synthesis And Doping Of ABO₃ Type Rare Earth Complex Oxide

ABO3 rare earth composite oxide system is a kind of extremely important functional material due to its excellent structure characteristics and application properties by slightly changing chemical composition.Doping substitution as an effective research method has been widely applied on investigating this system composite based on the characteristics.The structure of the ABO3 composite can be easily modified when the occupation of A and B atomic sites exchanges.As a result,the preparation process is beneficial to optimize the existing materials and obtain new functional materials with favorable physicochemical properties.The preparation of materials is an important part of material research.First,the properties of the material cannot be studied without the material.Besides,the material with same corriposition may eventually form different micro structures and exhibit different physical properties due to the use of different preparation processes.In the preparation process of ABO3 type composite oxide,high temperature solid phase method is a commonly used and relatively effective process with the advantage that the raw materials are mostly simple oxides with wide variety of sources and low price.Therefore,it is convenient for large-scale preparation.On the other hand,this method also has disadvantages as its reaction mechanism is a diffusion process in thermodynamics.That is,the diffusion process involved in this method is slow and must be completed at a very high temperature.In addition,this process must be repeated several times in high temperature to ensure a complete diffusion.However,even in this case,it is still difficult to guarantee all the atoms to experience the long-range migration completely.As a result,the chemical composition of the product is often uneven,which could make the study of perfomlance meaningless,In view of these shortcomings of the solid phase method,researchers are trying to explore new preparation processes,such as hydrothermal method,in which the preparation process is carried out after the reactive ions are mixed,and the ion diffusion occurs in the liquid phase.The advantage of this method is obvious,that is,it avoids the necessity of ions participating in the reaction in the solid phase reaction and the long-range migration is not required,which greatly reduces the activation energy of the reaction.Therefore,the reaction temperature is lower than that during the high-temperature solid phase method,and a uniform product can be obtained.In this study,we applied the hydrothermal process to synthesize ABO3 type rare earth composite oxides doped at the A-site and B-site,and characterized their crystal structure and magnetic properties.The first chapter is an introduction,summarizing the structural characteristics,magnetic properties and research progress of ABO3 composite oxides.The second chapter focuses on the preparation of ABO3 type rare earth composite oxides Tb1-xHoxMnO3(0≤x≤1)and Tb1-xHoxFeO3(0≤x≤1)by hydrothermal synthesis method.Tb1-xHoxMnO3(0≤x≤1)and Tb1-xHoxFeO3(0≤x≤1)are inter-doped with rare earth metal ions of different ionic radii at position A.In our study,we also explored the influence of different process conditions on the product,the changes in doping substitution at A-site,and the evolution of crystal structure,morphology and magnetic properties.Next,we present the preparation of ABO3 type rare earth composite oxides TbMn1-xFexO3(0≤x≤1))and HoMn1-xFexO3(0≤x≤1)by hydrothermal synthesis method in the third chapter.TbMn1-xFexO3(0≤x≤1)and HoMn1-xFexO3(0≤x≤1)are inter-doped with rare earth metal ions of different ionic radii at position B.The influence of different process conditions on the product was also studied.Along with the change of doping substitution of Fe at the B-site,the evolution of crystal structure,morphology and magnetic properties was analyzed.The fourth chapter discusses the preparation of Tb1-xHoxMn0.5Fe0.5O3(0≤x≤1)and Tb0.5Ho0.5Mn1-xFexO3(0≤x≤1)series compounds with A-site different ionic radius rare earth metal ions and B-site Fe ions by hydrothermal method.The evolution of product structure,morphology and magnetic properties were also measured and evaluated.In the fifth chapter,the research results of this study are summarized,and the future development of ABO3 composite oxides is prospected.