The crystal structures and dielectric properties of the (1-x)Ca(Mg1/2W1/2)O-3-xCaTiO(3) system

The crystal structures and dielectric properties of the (1-x)Ca(Mg1/2W1/2)O -3-xCaTiO(3) solid-solution system are investigated. This solid solution sy stem is single phase of perovskite-type structure in the whole composition range. It has been found that the Ti4+ ions almost equally substitute Mg2and W6+ site, not disturbing chemical ordering between Mg2+ and W6+. This d istinctive feature of substitution results in volume difference between the MgO6 and WO6 octahedra. Consequently, the crystal system changes from the monoclinic to orthorhombic with increasing Ti4+ substitution. Moreover, the relatively small Ti4+ substitution continuously decreases the unit cell vo lume. The structural changes are responsible for the temperature coefficien t change of dielectric constant (tau(epsilon)) which monotonically decrease s with increasing x. The dielectric constant (epsilon(r)) increases rapidly with increasing x. The relationship between crystal structures and dielect ric properties is presented.