Structural Disorder, Polarisation and the Normal to Relaxor Ferroelectric Transition in BaTiO3 Based Perovskites

This paper uses structured diffuse scattering to compare and contrast the local crystal structure behaviour of the normal ferroelectric BaTiO3 with a range of relaxor ferroelectric substituted BaTiO3 materials. The results strongly suggest that both normal ferroelectric BaTiO3 and the relaxor ferroelectric substituted BaTiO3's have the same underlying polarisation mechanism i.e. inherent 1-D correlated Ti cation and neighbouring O anion displacements forming 1-D dipole clusters (or polar nano regions). The role of the substituting ions is not to induce the PNR's but rather to suppress homogeneous strain distortion, transverse correlation of the 1-D PNR's and a transition into a long range ordered ferroelctric state.