Capacitance of material depends on its dielectric response ( permittivity). It is this property that makes these materials very attractive for high -k dielectric applications such as gate elements in MOSFET, RAM and multilayer capacitor. However, the range of temperature and frequency where high-K is observed depends upon the structural phase transition nature in a given material. Thus, the obvious question should be that what is the dielectric permittivity of a material. There are many materials which are neither feroelectric or multiferroic yet show gaint dielectric permitivity.

Dielectric permittivity indicates how readily a material can be polarized. But the origin of polarization can be different, either ionic or electronic.The material can be readily polarized in the unstable (dynamic) state. that's why we observe a high dielectric constant at the phase transition.  However in order to consider a material to be good dielectric, the polarization should be ionic in nature (good insulators with very small electronic polarization). the domination of electronic polarization is considered  as an anethma (Conducting materials). Both the ferroelectric PIN-PT and the partially (semi) conducting YCrO3 have the capacitance of the order of nF. However the PIN-PT is a good insulator  having ionic polarization whereas in case of YCrO3 electronic polarization  (due to d electrons of Cr) dominates. The conducting nature manifest as grain boundary and inter-facial polarization. As a result the YCrO3 shows large frequency dispersion  (interestingly dielectric constant decreases with time). consequently the YCrO3 cannot be considered as ferroelectric. Hence, not only the magnitude but the origin is also essential in the study of dielectrics.

thanks jeyaraj. u  answer my question. i have some doubts .is that YCrO3 electronic polarisation can be seen in MHz frequency range. YCrO3 is mentioned as weak ferroelectric in some papers of course their PE loops are horrible. is it so that dielectric constant in YCrO3 decreases with time or inverse of time. in conclusion we can say nF range related to grain bdry or interfacial polarisation but not from bulk contribution.

@Venkat venki. The electronic part is itself is of different origin. the atomic polarisibility where the electron cloud shift from the center of the ion, response to a very high frequency. on the other hand, the electronic polarization of d orbitals due to excitation,accumulates at the grain boundary and interfaces and their repose is limited to low frequency. in principle the electronic polarization due to atomic  polarisiblity will be seen at very high frequency and their contribution to dielectric constant is less than 10.

on doping the conductivity decreased, but does not improve the P-E loop indicates that  the P-E loop is not ferroelectric in origin (my observation). Thus the nF of YCrO3 is attributed due to grain boundary and interracial polarization clubbed as maxwell-wagner polarization.  But we cannot generalizing the statement, as the ferroelectrics which are good insulators have capacitance of the order of nF without the grain boundary and inter-facial contribution.

another way to differentiate these materials is the tan delta value which is around and above 1 for maxwell-wagner mechanism.