Dielectric Response in Microscopically Heterogeneous Dielectrics:   Example of KTaO_3:Nb
  New experimental data on solid solutions of quantum paraelectrics with KTaO_3:Nb as an example are considered within a framework of a quantum theory of ferroelectric phase transitions. In order to describe the effect of local heterogeneities a percolation type theory together with a random field approach were employed. 
S. Prosandeev, V. Trepakov, S. Kapphan, M. Savinov