The effect of crystal symmetry on the maximum polarization of polycrystalline ferroelectric materials

In polycrystalline ceramics, the degree of domain orientation in all possible crystal orientations contributes to the total realizable polarization. The extent to which domains are oriented towards an applied field can be described by a polarization distribution function. Such representations are calculated and presented in the present work for several different crystal systems including monoclinic symmetries that exhibit a polarization rotation mechanism. The relationship between the polarization distribution functions and the attainable macroscopic polarization is also developed for polycrystalline ceramics that are initially randomly oriented. In these cases, polarization rotation allows a significant degree of preferred orientation parallel to the electric field (>1000 multiples of a random distribution). However, the fraction of single crystal polarization that can be achieved (97.5%) is only marginally better than those of higher crystal symmetry.