Specific heat anomaly in ferroelectric: Bis(imidazolium) pentachloroantimonate(III) (C3 N2 H5)2[SbCl5]

• Heat capacity of ferroelectric (C3N2H5)2SbCl5 was measured.
• The Landau potential coefficients were calculated.
• The entropy excess ΔS ≈ 8.8 J mol−1 K−1 is characteristic of an ‘order-disorder’ mechanism of ferroelectric transition.

Single crystals of ferroelectric bis(imidazolium) pentachloroantimonate(III) (C3N2H5)2[SbCl5](C3N2H5)2[SbCl5] have been grown and the heat capacity was measured by the use of AC calorimetric method. The temperature dependence of excess heat capacity and excess entropy in the ferroelectric phase can be described in the frame of the classical Landau-Devonshire theory of phase transitions. The results of experimental studies were analyzed and the α, γ and δ values of the Landau potential coefficients were calculated. The temperature dependence of the order parameter was also evaluated from the heat capacity data.