Effects of average and local structure on the dielectric behavior of (1-x)BaTiO3-xLaYO(3) (0

The dielectric properties of dense ceramics of (1-x)BaTiO3-xLaYO(3) (LBTY) (0 = 0.20. The room temperature relative permittivity, epsilon(RT), decreases from similar to 2000 for x = 0.10 to similar to 57 for x = 0.40. This variation is accompanied by a substantial reduction in the temperature dependence of the relative permittivity, epsilon(r), and also by the emergence of relaxor ferroelectric-like behavior at x > 0.05. The gradual transition from a classical ferroelectric to a relaxor-type response results from disruption of the long-range ferroelectric order, believed to be caused by a nanoclustering phenomenon. x = 0.10 exhibits all the characteristic features of a relaxor-ferroelectric, i.e., epsilon(r) decreases and tan delta increases with increasing frequency. For x > 0.20 the relaxor behavior becomes progressively more subtle, suggesting a weaker coupling between the polar nanoregions. The poor microwave dielectric properties of LBTY ceramics, in particular for x = 0.40, which exhibit epsilon(RT) similar to 57 and a quality factor of similar to 755 GHz are attributed to phase separation on the nanometer scale. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3459897]