| The paper describes the development course and application of ultrasonic transducer materials, and has carried on the system of narration for piezoelectric materials composition, properties, structure and so on. Piezoelectric effect is introduced and its forming conditions and the ferroelectric crystal polarization of types, mechanism, electricity domain, the relationship between polarization and the applied electric field. Since1952the American B.Jaffe et al. found that PZT solid solution system-the lead zirconate titanate with its superior performance long-term in a dominant position in the field of piezoelectric ceramics. And it is widely used in various fields. The lead-based piezoelectric materials in the process of production, useness and it’s waste treatment etc. also brought potential threat to human survival environment. At present, with the improvement of human environmental protection consciousness and the need of sustainable development,research and development of new types of lead-free piezoelecteic ceramics has become a new topic in today’s world.Used for artificial piezoelectric crystals of hf(high frequency) and uhf(ultra-high frequency) detection is by changing its chemical composition, formulation, preparation technology to adjust its properties to make it adapt to the different meeds. The compared commonly used artificial crystal are piezoelectric ceramic, polar polymers and piezoelectric composite materials, etc. The second chapter discusses the structure, performance parameters of piezoelectric ceramic materials (free dielectric constant, dielectric loss, elasticity coefficient, mechanical, quality factor, piezoelectric constant, electromechanical coupling coefficient and frequency, etc.) and the preparation process. Every detail in the process of preparation of the samples is directly related to the implementation of the performance. So the strict control of process conditions is particularly important. The fourth chapter focuses on the structure of the new lead-free BNT piezoelectric ceramic materials and it’s craft. Due to sodium bismuth titanate ceramics (BNT) dielectric coefficient, electromechanical coupling coefficient, piezoelectric constant are big and small dissipation, it will be chosen for doping modification to improve the performance of piezoelectric research subject. Firstly, the simple introduction and comparison are given of the structure, piezoelectric, dielectric properties, acoustic properties of the practical system—the five types of lead-free ceramics are:barium titanate ceramics, bismuth layer structure, alkali metal salt seriea, tungsten bronze niobate ceramics and sodium bismuth titanate based ceramics. Secondly, from the selection of raw materials, ceramic powder processing and handing technology, ceramic body molding and firing technology of ceramic materials, BNT based ceramic is discussed-the several common preparation methods such as solid phase method, hydrothermal method, sol-gel technology, molten salt method,etc. Lastly, the paper described in detail the BNT-BKT experiment materials and equipment, the specific experiment methods and processes. At the same time, according to the trace element doping modification principle and experience screening got good BNT-BKT ceramics for doping modification research.The paper adopted the traditional solid-phase synthesis. The raw materials are synthetic analysis of pure, the powder processing and preparstion adoped solid consistency, samples taking the dry pressing molding, and in high temperature solid phase sintering method. The three-four type with the phase boundary of ceramics system (1-x)BNT-xBKT in the range x=0.16-0.22, and requiring low polarization voltage and can be by changing the preparation technology of the piezoelectric performance boost.The ceramic material Bio.s(Nao.8Ko.2)o.sTi03+Xwt%SrC03is this paper’s research object. It choosed different sintering temperatures between1100-1200℃, and prepared the ceramic materials containing SrCO3different doping amount. And each of these components of different formula of ceramic material chemical composition has been tested and its microstructure has been analysed. Studied under the condition of appropriate preparation of BNT-BKT that doped SrCO3test results and morphology. According to the results, the ceramic grain geometric shape feature is obvious, grain boundary clear, good density piezoelectric performance is also improved. |
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