Microwave Dielectric Properties of Bi-Added Ba₄Nd_9+1/3Ti₁₈O₅₄ Solid Solutions

We have investigated the formation and microwave dielectric properties of the tungstenbronze-type like solid solutions, that is, Bi ions dissolved in Ba_6-3xNd_8+2xTi₁₈O₅₄ solid solution with x=2/3. According to the increase of y in the Ba₄(Nd_1-yBi_y)_9+1/3Ti₁₈O₅₄ compositions, the change of the lattice parameters has an inflection point at y=0.05. Bi was substituted into A2 sites for Ba up to y=0.05 and into A1 sites for Nd over y=0.05. As y increased, the dielectric constant, ε_r, increased and the quality factor, Q·f, decreased. The temperature coefficients of the resonant frequency, τ_f, improved to 17 ppm/°C at y=0.15. The relationship between the lattice parameters and the microwave dielectric properties of the Bi-added Ba₄Nd_9+1/3Ti₁₈O₅₄ solid solutions is also presented.