Comment on '[N(CH3)3H]2ZnCl4: Ferroelectric properties and   characterization of phase transitions by Raman spectroscopy'
  The authors of paper commented claim that trimethylammonium tetrachlorozincate crystal shows at 282 K the ferroelectric-paraelectric phase transition. But no ferroelectric hysteresis loop was observed below this temperature. Moreover, in the low-temperature phase the ferroelectric domain walls should exist giving dielectric relaxation in a low frequency electric field. The authors conclude that the phase transition is of the second order. This conclusion is contrary to the DSC data where the phase transition has a strong first order character. In the whole measured temperature range the dielectric loss is 100 times higher than the real part of dielectric constant. 
Zbigniew Tylczynski
cond-mat.mtrl-sci