Hey All, This is a question I have faced many times, but I never fully grasp the difference. All ferroelectrics are piezoelectric, but not all piezoelectrics are ferroelectric.... I understand that ferroeletrics are due to their noncentrosymetric crystal structure and they can therefore have a spontaneous polarization. And Piezoelectrics can generated voltage and reverse their polarization about the application of a stress. But I dont understand the relationship mentioned above. How can a piezoelectric not be ferroelectric as well. Quartz is an example of this. I believe this is because of the crystal structure and ion charge balance present in the crystal structure. Therefore quartz will NOT have spontanous polarization, but if a stress is applied to its crystal structure a charge potentail can be created. Any insight how to clearly or better understand this and explain the difference would be greatly apperciated!!