Discrimination of the transition order extremely close to a tricritical point

The cubic to tetragonal phase transition of the ferroelastic KMn0.997Ca0.003F3 has been studied by a conduction calorimetry technique. The comparison of the specific heat data, the sensitivity of the calorimeter and the DTA trace obtained with the same apparatus and under similar thermal conditions shows that the transition is extremely close to the tricritical point and its latent heat is evaluated to be 0.010±0.005 J g−1.