Phase Equilibria and Crystal Chemistry of the Binary and Ternary Barium Polytitanates and Crystallography of the Barium Zinc Polytitanates

The ternary system BaO-ZnO-TiO2 is of great interest for use in the production of microwave dielectric ceramics, as the temperature coefficient of the dielectric constant for a ternary phase in the system has the opposite sign from that of the major component in such devices, BaTi4O9. The ternary system has been found to contain four ternary phases, ideally BaZn2Ti4O11, Ba4ZnTi11O27, Ba2ZnTi5O13, and BaxZnxTi8-xO16-hollandite. Compatibility triangles for the ternary system have been established and the crystal chemistry and crystal structure of each of the phases was investigated. The phase equilibria data and crystal structures are compared with those encountered in the binary system and other ternary and more complex systems involving barium polytitanates.