Domain size effects in a uniaxial ferroelectric relaxor system:: The case of SrxBa1-xNb2O6

We present investigations of the domain dynamics and of the evolution of the critical exponent beta in a ferroelectric relaxor system, exemplarily in the up-to-date controversial strontium barium niobate (SBN). k-space spectroscopy at the phase-transition and when applying an electric field reveals a size-dependent response of the domains. This is supported by pyroelectric measurements that show, by analysis in terms of criticality, the critical exponent beta is not only dependent on the level of poling but also on the manner in which the poling was achieved. It must be concluded that the crystals undergo a phase transition not-as commonly assumed-in a uniform way with homogeneous polarization throughout the crystal. Instead they behave as a set of more or less independent domains with size-dependent stability. Therefore, one should be very careful with critical exponents-especially those derived from experiments that explicitly or implicitly-assume a uniform polarization behavior. (c) 2007 American Institute of Physics.