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The influence of hydrostatic pressure on the Curie temperature of BaTiO₃ single crystals has been investigated. With increasing pressure a linear shift of the Curie point towards lower temperature is observed with a slope of -5. 810^-3 degree/atmos. This information allows us to calculate the change of the specific heat and of the compressibility at the Curie point according to Ehrenfest's relation. Thus it is possible to relate the pressure effect to the change of the lattice constant. The decrease of the Curie temperature with shrinking lattice constant is nearly the same as that observed when Sr ions are substituted for Ba in the titanate crystal. In addition, measurements have been made on the influence of pressure on the first order transition point near 0^.
W. J. Merz (Sat,) studied this question.