Self polarization in relaxor Pb(Mg1/3Nb2/3)O 3 thin films

Pb(Mg_1/3Nb_2/3)O₃ (PMN) thin films were prepared from alkoxide-based solution precursors. Dielectric and electromechanical measurements were carried out. Piezoelectric response of as-prepared films was found to be large (d₃₃=10-20 pm/V) even in absence of a DC bias field. The value of the associated self polarization in the films is estimated and its presence confirmed by zero-field pyroelectric measurements. The electrostrictive Q coefficient was determined by measuring strain (S) vs. electric field (E_ac) and polarization (P) vs. electric field (E_ac) loops on the same sample and under identical conditions. This allowed us to plot S vs. P² relationship without any approximations and to determine the Q coefficient (Q=1.18×10^-2 m⁴C^-2)