SPECIFIC-HEAT UNDER UNIAXIAL-STRESS

An experimental approach for the adaptation of conventional calorimetr ic techniques for measurements under uniaxial stress is reviewed. Spec ial attention is focused on the description of the use of the a.c. met hod for measuring specific heat under uniaxial stress. The application of isoperibolic calorimetry to specific heat measurements under uniax ial stress is described in detail. The method has been tested at low s tress by studying the influence of uniaxial stress on the change of di mensionality of the order parameter of strontium titanate. Measurement s of the specific heat and heat power exchanged by a deuterated dihydr ogen potassium phosphate sample at the ferroelectric-ferroelastic phas e transition are also included. These measurements show the advantages of this method for the study of first-order transitions under uniaxia l stress.