I measure dielectric permitivvityversus T in bulk BaTiO3 samples .It is known that when it undegoes from paraelectric to ferroelectric(cubic to tetragonal) it exhibits a first order transition and thermal hysterisis is expected. I also observed thermal hysteris on the transitions to lower temperatures, i.e when it undergoes from tetragonal to orthormobic, and orthorombic to romboedric, but aren't these transitions regarded to be as second order and thus, I should not see thermal hysterisis?
no, unlike first order transformation , the second order transformation is not an activation energy driven transformation.
everything is actually nucleation and growth, BaTiO3 is already 1th order and there is no ecaxt and clear evidence for 2thorder.
Thank you all for the contribution! It is accepted generally that there should be no hysteresis in 2nd order transition, however I do observed it. Satya, good to know that it has also been observed in similar cases, thanks.
Some of the claims of thermal hysteresis for a second order phase transition are of spurious origin. The group sub group relation from ITC vol B will help you to resolve the possibility of having a intermediate phase which leads to a first order phase transition.
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