The Significance of the Burns Temperature in Relaxor PMN
  We suggest considering the Burns temperature in lead containing relaxor ferroelectrics as the temperature, at which Pb becomes off-center and nearly randomly occupies positions around the center on a sphere with the radius, which increases with the temperature decrease. The significance of the Burns temperature, in this approach, is the crossover between the soft-mode and order-disorder dynamics. The lattice parameter, birefringence and neutron scattering experiments are analyzed in the light of this model. 
S.A. Prosandeev, S.B. Vakhrushev, N.M. Okuneva, P.A. Markovin, I.P.   Raevski, I.N. Zaharchenko, M.S. Prosandeeva