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Title: Synthesis and Characterization of BNT based Magnetoelectric Composites
Authors: Singh, Parminder
Supervisor: Kolte, Jayant
Sharma, Puneet
Keywords: Magnetoelectric;Composites;Cermics;Ferrites;Piezoelectric;Ferroelectric
Issue Date: 26-Feb-2024
Abstract: The magnetoelectric (ME) composites has gained great deal of attention over to single phase multiferroics due to its strain mediated coupling between piezoelectric and magnetostrictive phases. Such composites with high coupling have paved the way for practical device application in meRAMs, sensors, and low frequency energy harvesters etc. The resultant ME coupling depends upon the type of magnetic and piezoelectric phase, their relative fraction, and type of geometry. Amongst lead-free piezoelectric materials, BNT-based ternary solid-solution, i.e., 72.5Bi0.5Na0.5TiO3-22.5Bi0.5K0.5TiO3-5BiMg0.5Ti0.5O3 (BNKMT) is prominent due to its excellent piezoelectric coefficient. On the other hand, NiFe2O4 or Ni1-xZnxFe2O4 (x = 0 - 0.5) exhibit high piezomagnetism. Therefore, in this work, the main focus is to study the influence of relative weight fraction and geometry on the magnetoelectric coupling of their composites. The work is organized into seven chapter, where the content of each chapter is shown below. Chapter 1 (Introduction): This chapter provides a concise introduction about magnetoelectric (ME) properties in multiferroic materials. Further, an overview of ME coupling in single-phase multiferroics and composites is given. Some basic definitions and terminology used in the thesis are given along with their important role in ME properties are discussed. The factors that influence the ME coupling in composites are discussed in detail. At last, applications of ME composites in several areas are highlighted. Chapter 2 (Literature review): This chapter is mainly focused on the factors that have influence on the ME coupling of composites. Initially, the impact of substitution and doping on the BNT-based solid solutions is reviewed followed by the effect of substitution on magnetostrictive phase. The ME coupling in particulate and laminates has been discussed. The effect of phase fraction and applied f of H on ME coupling among particulates and laminates is also presented. Based on these studies, the literature gap is discussed followed by the objectives for the research work. Chapter 3 (Experimental and characterization techniques): This chapter includes the synthesis method for developing PE phases (BNT and BNKMT), magnetostrictive phases (NZxFO) and their 0-3 and 2-2 composites. A brief detail of novel direct diffusion bonding technique is given for synthesizing 2-2 composite. Further, several material characterization techniques have been explained in the final section of this chapter. Chapter 4 (Results and discussion: Pure Phases): In this chapter, the synthesis and optimization of both PE and magnetostrictive are discussed. This chapter is categorized into four sections. In first two sections, the effect of sintering temperature on the structural and electrical properties of PE BNT and BNKMT phases has been investigated. In the third section, the influence of sintering temperature on the structural and magnetic properties of NFO is presented. In the last section, effect of Zn substitution on the magnetic properties of the optimized NFO has been discussed. Chapter 5 (Results and discussion: Magnetoelectric 0-3 composites): In this chapter, the phase, structural, electrical, magnetic and ME properties of 0-3 composites has been investigated. The chapter is divided into four sections. In the first section, the ME coupling in (1-x)BNT-xNFO composites are examined. Second section is focused on the ME coupling of (1-x)BNKMT-xNFO composite. These two sections demonstrate the effect of PE phase on ME coupling. In third section, the effect of magnetostrictive phase on the ME coupling has been studied by varying Zn substitution in NFO coupled with BNKMT in a fixed weight proportion, i.e., explore the ME coupling in 0.8BNKMT-0.2NZxFO composite. The last section emphasizes on the ME coupling based on the suitable PE (BNKMT) and magnetostrictive (NZ0.3FO) in variation of relative weight fraction. Chapter 6 (Results and discussion: Magnetoelectric 2-2 composites): In this chapter, the structural, FE, magnetic and ME properties of the laminate composite has been examined. The bilayer and trilayer laminate composites of BNKMT and NZ0.3FO are synthesized via novel direct diffusion bonding technique. Chapter 7 (Conclusions): A summary of the results from the diverse experiments discussed in the previous chapters are presented in this chapter. Initially, the effect of varying relative weight fraction on ME coupling in 0-3 composites is outlined. The impact of bilayer and trilayer laminates on the ME coupling has been concluded. At the end, the potential avenues for further research are discussed in the future scope section.
Appears in Collections:Doctoral Theses@SPMS

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