A single electric relaxation time in Ba_1−<i>x</i>Sr_<i>x</i>TiO₃nanoparticles at low temperatures

It is shown that the dielectric response of Ba(0.77)Sr(0.23)TiO(3) nanoparticles at temperatures below 200 K has a frequency and temperature dependence in agreement with the Debye theory with a single relaxation time, which exhibits the Arrhenius law. By contrast, at temperatures above 210 K the dielectric response exhibits a broad range of relaxation times characteristic of relaxor-ferroelectrics. We suggest that the single relaxation time at low temperature originates from a frustration effect, in analogy with frustrated antiferromagnetism.