Structure evolution in the La{sub 2}MgTiO{sub 6}-Ba{sub 2}MgWO{sub 6} system

The crystal structure of dielectric ceramics in the (1-x)La{sub 2}MgTiO{sub 6} (LMT)-xBa{sub 2}MgWO{sub 6} (BMW) system has been studied by X-ray powder diffraction and transmission electron microscopy. LMT and BMW were found to form solid solutions in the whole compositional range. Increase of BMW content results in two structural transformations: continuous P2{sub 1}/n->I2/m at x between 0.2 and 0.25 and discontinuous I2/m->Fm3-bar m at x between 0.4 and 0.5. This sequence of the phase transitions is compared with structural transformations in other solid solutions between dielectric complex perovskites. It is supposed that the discontinuity of the I2/m->Fm3-bar m phase transition might contribute to some peculiarities in the compositional dependence of dielectric characteristics of this system.