Differences between para and ferroelectric materials

[Twickel]

Hi
I am having toruble differentiating between the two. below the curie temperature BaTiO3 behaves as a ferroelectric, the Ti ions are offset from the centre, causing a polar domain. But it has a net polarisation is zero.

Now above the curie temperature all the dipole cancel each other out so it also has a net oikarisation of zero.

So what is the difference in terms of orientation of domains/structure? Are they both unordered since they both have net polarisations of zero?

 

[leontel]

Hi there,
I would try to answer your question. Basically, you question involved two different scope. The first is the atomic scope, in which, as you said, ferroelectric features with spontaneous polarization and paraelectric does not. However, when comes to the macro scope, the virgin ferroelectric includes all these spontaneous polarization randomly, producing a zero output, the same as the paraelectric. There is one way to distinguish these two. By only applying an external field to the material, the spontaneous polarization will align to the field and exhibit an finite polarization which will not disappear after the external field is removed, while in the case of paraelectric, the net polarization after the external field removal is still zero.