GROWTH AND DIELECTRIC-PROPERTIES OF CONGRUENTLY MELTING BA1-XCAXTIO3 CRYSTALS

The phase diagram of the system BaTiO3-CaTiO3 is investigated with reg ard to a congruently melting composition. The liquidus curve is determ ined from x = 0.0 to 0.3, where x is the mole fraction of CaTiO3. It s hows a minimum melting point near x = 0.23. Ba1-xCaxTiO3 crystals are grown by the Czochralski technique from melts close to this compositio n. X-ray fluorescence analyses of the crystals indicate a congruently melting composition at x = 0.227, corresponding to the observed minimu m melting point. At the growth temperature the crystals possess a cubi c perovskite-type structure. They undergo a structure change to the fe rroelectric tetragonal phase at 98 +/- 3 degrees C, indicated by a sha rp peak of the dielectric constant. Down to -120 degrees C no further phase transition is observed.