Does Burns Temperature Exist in Ferroelectric Relaxors?

It has for a long time been considered that polar nanoregions in relaxors form at Burns temperature T-d approximate to 600 K. Dielectric investigations of Pb(Mg1/3Nb2/3)O-3 (PMN) and 0.7PMN-0.3PbTiO(3) systems, performed in a broad temperature range, and the analysis of the intrinsic response in terms of the universal scaling imply, however, much higher T-d or formation of polar nanoregions in a broad temperature range. High values of the dielectric constant manifest that polar order already exists at the highest measured temperatures of 800 K. The obtained values of critical exponents indicate critical behavior associated with universality classes typically found in spin glasses.