Dissertation > Excellent graduate degree dissertation topics show

Compositional Design and Modification of BNBKT Lead-free Piezoelectric Ceramics

Author: YeChun
Tutor: ZuoRuZhong
School: Hefei University of Technology
Course: Materials Science
Keywords: lead-free piezoelectric ceramic morphotropic phase boundary (MPB) relaxor ferroelectric “donor”and“acceptor”additive low-temperature sintering
CLC: TM282
Type: Master's thesis
Year: 2009
Downloads: 123
Quote: 1
Read: Download Dissertation

Abstract


Sodium bismuth titanate (Bi0.5Na0.5)TiO3(BNT), which has strong ferroelectric properties at room temperature, is a kind of A-site perovskite-type ferroelectric with relatively high Curie temperature 320 oC and large remanent polarization 38μC/cm2. Therefore, BNT-based lead-free ceramic has been considered to be one of the most promising candidate materials for lead-based ceramics at the advantages of excellent electrical properties and environment friendly. In this paper, lead-free (1-x)(0.968Bi0.5Na0.5TiO3-0.032BaTiO3)-xBi0.5K0.5TiO3 (BNBKTx) ternary system piezoelectric ceramics were desigined by linear combination rule, and optimized by doping and reducing the sintering temperature.BNBKTx ceramics were prepared by conventional solid-state reaction method. The XRD results show that all BNBKTx ceramics have pure pervoskite structure and the MPB is loacated at the composition range of 0.08≤x≤0.10. The electrical properties and phase diffusion of the BNBKTx ceramics near MPB were studied. The results show that BNBKT9 has lower coercivity field near MPB with Ec=1.98kV/mm and the best piezoelectric properties of d33=162p C/N, kp=31%. It is also found that the BNBKTx ceramics are typical relaxor ferroelectrics, whose degree of diffuseness are increasing with the increase of BKT.The microstructures and electric properties of BNBKT9 doped by Sb2O3 were investigated. XRD results indicate that as Sb2O3 is doped with x < 0.02, BNBKT9-xSb ceramics owned the same pure perovskite structure as the matrix; the second phase developed at the range of 0.02≤x≤0.04. Sb2O3 seems to act as "donor" and "acceptor" because of its variable valences, which can change the electric properties to“soft”or“hard”. When x≤0.005, the piezoelectric constant d33 and the electromechanical coupling coefficient kp increase with the increase of Sb2O3 content, but the mechanical quality factor Qm decreases, exhibiting characteristics of“soft”additives. On the contary, a hard property was induced when x>0.005 at which Qm increases and kp decreases. The ferroelectric and piezoelectric properties of BNBKT9-xSb ceramics with excess addition of Sb2O3 (0.02≤x≤0.04) dropped dramatically, which could be related to the formation of antiferroelectric micro-domain at room tempature. The low-temperature sintering and electric properties of BNBKT9-0.5Sb ceramics aidded by CuO were studied. The sintering temperature can be reduced to about 1060°C, which is lower than that of the matrix, and the density of doped samples is up to 98% of theoretical value. It is due to a lower melting point of CuO, which produces a liquid phase during sintering. The dielectric loss tanδof ceramics increases with the CuO addition, which indicated that the ionic conductivity is increasing. The interfacial polarization of ceramics containing higher content of CuO contributed to the increasing of dielectric constant under low-frequency condition. At the same time, the CuO addition induces the piezoelectric properties to“hard”. With the addition of CuO, both d33 and kp reduce, but Qm increases.

Related Dissertations

  1. Lithium anode material calcined alumina crucible Development,TQ174.6
  2. Study on Low Temperature Sintered PSN-PZT Piezoelectric Ceramics,TM282
  3. Li ferrite temperature Preparation and simulation applications,TM277
  4. Effects of Sintering Additives on Sintering Characteristics and Thermoelectric Properties of LaCoO3 Ceramics,TQ174.651
  5. Research on Electrical and Magnetic Properties of Composite Garnet Ferrite Sintered at Low-temperature,TQ138.11
  6. The Study on Low-temperature Sintering of Alumina Ceramic and Its Metallizing,TQ174.1
  7. Molten salt prepared niobium , zinc - based microwave dielectric ceramics structure and properties of,TQ174.1
  8. The Method for Complex Electromechanical Coefficients of Relaxor-Based Ferroelectric Crystal Pb(Mg1/3Nb2/3)O3-PbTiO3,TM306
  9. Research of Shear Mode Pmn-pt Single Crystal Transducer,TM282
  10. Study on Preparation and Size Effect of Fine Grain High Temperature BiScO3-PbTiO3 Ceramic,TQ174.75
  11. Research on Preparation and Properties of xLiNbO3-（1-x）(K0.5Na0.5)NbO3（LNKN） High-temperature Lead-free Piezoelectric Ceramics with High Content of Lithium,TQ174.75
  12. The Crystallization Characters and Application Study of the Low Temperature Processed BaO-Al2O3-SiO2 Glass-Ceramics,TQ171.733
  13. The Study of Electronic Magnetic Properties of the Low-Temperature-Sintered Hexagonal Ferrites,TM277
  14. BST Ceramics for Middle-high Voltage Capacitors,TM28
  15. Low-Temperature Sintering of ZnNb2O6 Ceramics,TQ174
  16. Study on High Temperature Creep Property of Uranium Dioxide Pellet,TB302.3
  17. Research and Preparation on the Low Temperature Sintering of PZT-based Piezoelectric Ceramics,TM282
  18. The Low Temperature Firing and Dielectric Properties of Cblst Ceramic and Clnt Ceramic,TQ174.1
  19. Studies on Molten Salt Approach and Low Temperature Sintering of ZnO-TiO2-based Microwave Dielectric Ceramics,TQ174.651
  20. Mechanism and Preparation of Cordierite Powder Synthesized by Microemulsion-Sol Gel Technique,TB383.3

CLC: > Industrial Technology > Electrotechnical > Electrical materials > Electric and ceramic materials > Piezoelectric ceramics
© 2012 www.DissertationTopic.Net  Mobile