Sintering behavior and microwave dielectric properties of Bi 3(Nb 1− xTa x)O 7 solid solutions

Abstract

Solid solutions of Bi 3(Nb 1− x Ta x )O 7 ( x = 0.0, 0.3, 0.7, 1) were synthesized using solid state reaction method and their microwave dielectric properties were first reported. Pure phase of fluorite-type could be obtained after calcined at 700 °C (2 h) −1 between 0 ≤ x ≤ 1 and Bi 3(Nb 1− x Ta x )O 7 ceramics could be well densified below 990 °C. As x increased from 0.0 to 1.0, saturated density of Bi 3(Nb 1− x Ta x )O 7 ceramics increased from 8.2 to 9.1 g cm −3, microwave permittivity decreased from 95 to 65 while Q f values increasing from 230 to 560 GHz. Substitution of Ta for Nb modified temperature coefficient of resonant frequency τ f from −113 ppm °C −1 of Bi 3NbO 7 to −70 ppm °C −1 of Bi 3TaO 7. Microwave permittivity, Q f values and τ f values were found to correlate strongly with the structure parameters of fluorite solid solutions and the correlation between them was discussed in detail. Considering the low densified temperature and good microwave dielectric proprieties, solid solutions of Bi 3(Nb 1− x Ta x )O 7 ceramics could be a good candidate for low temperature co-fired ceramics application.