Effect of Ta₂O₅ Content on Microstructure and Dielectric Properties of Ba₂NbNb_{5(1 - x)}Ta_5xO₁₅ Ceramic

ABSTRACT

In order to engineer the dielectric characteristics of Ba₄Na₂Nb₁₀O₃₀ (BNN), homovalent cation Ta^{5 +} was substituted for Nb^{5 +}. The samples were prepared through the general solid state reaction process. After sintering, phase development, sintering behavior and dielectric characteristics of the samples were examined as a function of Ta content. An entire solid solution between BNN and BNT was observed and the optimum sintering temperature increased as the content of Ta increased. Lattice constant of BNN was dependent on the content of Ta even though the ionic radii of Nb and Ta were the same. A relationship between the phase transition temperature and the lattice constant was observed. The dielectric characteristics were explained with the degree of disorder due to the substitution of Ta, and the simulation of the degree of disorder well agreed with the experimental results.

Keywords:

• Tungsten bronze structure
• BNN
• BNT
• ferroelectrics
• diffuse phase transition

Acknowledgement

This work was supported by Grant No. R01-2003-000-11606-0 from the Basic Research Program of the Korea Science & Engineering Foundation.