Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (08): 2009-2014.doi: 10.3866/PKU.WHXB20110839

• PHYSICAL CHEMISTRY OF MATERIALS • Previous Articles    

Conductivity and Dielectric Loss of Tungsten-Bronze-Type BaNd2Ti4O12 Microwave Ceramics

XIA Hai-Ting1,2, KUANG Xiao-Jun3, WANG Chun-Hai1, LI Wen-Xian2, JING Xi-Ping1, ZHAO Fei4, YUE Zhen-Xing4   

  1. 1. Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China;
    2. College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, P. R. China;
    3. MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, P. R. China;
    4. State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, P. R. China
  • Received:2011-04-29 Revised:2011-06-12 Published:2011-07-19
  • Contact: KUANG Xiao-Jun, JING Xi-Ping E-mail:kuangxj@mail.sysu.edu.cn. xpjing@pku.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20821091, 21071009, 20423005).

Abstract:

Tungsten-bronze type titanate BaNd2Ti4O12 ceramics were synthesized by solid state reactions. The conductivity and microwave dielectric loss of the samples that were thermally treated under various conditions and Ta-doped were investigated by electrochemical impedance measurement and microwave dielectric resonator measurement. The variation in conductivity with annealing atmospheres of air, O2, and N2 was consistent with the defect equilibriums 2OO×↔2VO··+O2↑+2e' and TiTi×+e'↔Ti'Ti, suggesting n-type conductance for BaNd2Ti4O12. Thermal treatment in air/O2 was found to favor the elimination of the native defects VO×, Ti'Ti and weakly bound electrons thus decreasing the conductivity. Thermal treatment in a N2 atmosphere, which had a low oxygen partial pressure, increased the defect content and the conductivity. Thermal treatment in air/O2/N2 did not clearly affect the microwave dielectric loss, suggesting that native defects have negligible effects on this property. The air-annealed sample was found to have lower conductivity and lower microwave loss compared with the air-quenched sample. The change in conductivity was found to be related to the equilibrium of the native defects but the change in microwave dielectric loss might be explained by the release of thermally induced lattice strain. Ta doping reduced the conductivity but increased the microwave dielectric loss. This work shows that air-annealing may be an efficient way to improve the Q×f factor for BaNd2Ti4O12 ceramics, which was enhanced by ~12%.

Key words: Defect, Conductivity, Microwave dielectric loss, BaNd2Ti4O12, Tungsten-bronze

MSC2000: 

  • O646