Site occupancy of Bi ions and microwave dielectric properties in Bi-doped Ba6−3xR8+2xTi18O54 (R = rare earth, x = 2/3) solid solutions

The tungstenbronze-type like Ba6−3xR8+2xTi18O54 (R=rare earth) solid solutions, which have excellent microwave dielectric properties, have been investigated about the effect of substituting Bi ions on the lattice parameters and the phase structure. The x-values for the Ba6−3x(R(8+2x)−yBiy)Ti18O54 formula were fixed at x=2/3, and the y-values were varied from 0.0 to 0.3. In the case of La and Nd series which are widely used in the dielectric resonator applications, it seems that until y=0.05 Bi ions substituted for Ba ions, and thereafter for La or Nd ions from y=0.05 to 0.3. In the case of La and Nd series, the dielectric constant (εr) decreased in the early stage of 0