Microwave Dielectric Properties of Low-Temperature Sintered Bi2[Zn1/3(Nb1-xTax)2/3]2O7

Abstract

After Bi₂(Zn_1/3Nb_2/3)₂O₇ (BZN) and Bi₂(Zn_1/3Ta_2/3)₂O₇ (BZT) were calcined at 900 ºC and then sintered at 900 ºC, respectively, microwave dielectric properties of BZN were quality factor (Qf₀) = 3,584 GHz, dielectric constant (e_r)=77 and temperature coefficient of resonant frequency (t_f) = -34.2 ppm/ºC. Those of BZT were Qf₀ = 3,640 GHz, e_r = 64 and t_f = 2.2 ppm/ºC. These two bismuth (Bi) based composition are known to be adequate for microwave application. However BZT has superior Q·f₀ to BZN, but higher sintering temperature which make BZT difficult for co-firing with Ag electrode, while BZN can be co-fired with Ag electrode, but lower Qf₀ than BZT. Therefore in this study, Bi₂[Zn_1/3(Nb_1-xTa_x)_2/3]₂O₇ (BZNT), solid solution between BZT and BZN, was synthesized and sintered at various temperatures for investigation. As amount of Ta substituting Nb increased, sintered density and Q·f₀ increased while e_r decreased. Temperature coefficient of resonant frequency (t_f) changed from negative to positive region. When BZNT (x = 0.5) was sintered at 900 ºC, dielectric properties were Qf₀ = 4,229 GHz, e_r = 71 and t_f = 24.7 ppm/ºC.