Doping mechanism and permittivity correlations in Nd-doped BaTiO3

BaTiO3 forms an extensive range of solid solutions with Nd2O3 by means of the double substitution mechanism: Ba + Ti double right arrow 2Nd, as shown by both a phase diagram study and Rietveld refinement using powder neutron diffraction data. The solid solutions have the general formula Ba1-xTi1-xNd2xO3:O less than or equal to x less than or equal to 0.12 at 1300 degrees C and 0 less than or equal to x less than or equal to 0.14 at 1400 degrees C. With increasing x, the symmetry changes from tetragonal to cubic at x similar to 0.09. The sharp permittivity maximum at similar to 127 degrees C in stoichiometric BaTiO3 broadens very rapidly with increasing x and gradually moves to lower temperatures: this appears to be because, with substitution of Nd onto Ti sites, formation of the ferroelectric domains is increasingly difficult because of the presence of dipole-inactive Nd3+ ions on the Ti sites.