Effect of annealing on the charge-voltage characteristics of the   SrBi2(Ta,Nb)2O9 films
  The effect of changes of the Nb content and annealing on charge vs. voltage and current vs. voltage characteristics of SrBi2(Ta,Nb)2O9 film was studied theoretically and experimentally. Theoretical modeling, which takes into account the mobile charged donors impact on the features of charge vs. voltage and current vs. voltage characteristics of ferroelectric semiconductor films, revealed the changes of conductivity value and ferroelectric parameters. The results of theoretical analysis and experimental results are in qualitative agreement. 
N.V. Morozovsky, A.V. Semchenko, V.V. Sidsky, V.V. Kolos, A.S.   Turtsevich, E.A. Eliseev, and A.N. Morozovska
cond-mat.mtrl-sci