抄録
The temperature change in lattice parameters of solid solutions of barium titanate containing 10, 12, 20 and 25 mole per cent of lead titanate have been studied mainly by the X-ray method for the range from −130°C to 300°C. It was found that the lattice parameter-temperature curves for the solid solutions of 12 and 20 per cent lead titanate have characteristic features as follows:
(1) a-parameter-temperature curves show a considerable linearity from lower temperatures up to the Curie point.
(2) A large amount of discontinuity of a- and c-parameters takes place at the Curie point.
(3) The superposition of cubic lines upon tetragonal lines is observed in a temperature range near the Curie point. The lattice volume calculated from tetragonal phase shows an abnormal contraction.
These results are not explained by the Devonshire’s theory in its original form, but they can be explained fairly well by using higher order approximation.
