Temperature compensated microwave dielectrics based on lithium containing titanates

Ceramic materials in the system Ln2/3−x3+Li3x1+TiO3 (Ln=rare earth element), which are known to exhibit lithium ion conductivity, were examined over wide frequency and temperature ranges with regard to their conductivity (σ) and dielectric properties (ε and tg δ). In the microwave range both positive temperature coefficient of dielectric constant (τε) and dielectric loss magnitude in lithium containing materials Ln2/3−xLi3xTiO3 can be ascribed to the presence of lithium-ion conductivity. The substitution of rare-earth ions with smaller ionic radii for larger La ions suppresses both the cation conductivity and dielectric losses. In this case Li ions do not participate in conductivity but contribute noticeably to the relaxation. The latter results in the positive τε and relatively low tg δ. Using the system Ln2/3−xLi3xTiO3 as an example it has been shown that the materials with the mobile lithium cation sublattice can be used for the volume temperature compensation of microwave (MW) dielectrics with the negative τε.