Time-domain THz transmission and FTIR reflectivity spectra of dense core–shell

composites of the BaZr0.2Ti0.8O3, BaZr0.4Ti0.6O3, Ba0.66Sr0.34TiO3 and

Ba0.45Sr0.55TiO3 compositions were studied at 10 to 900K. The spectra were

evaluated to obtain the complex dielectric functions and at room temperature they

were compared with the prediction of the generalized brick-wall model based on

the effective medium approximation. The model was analysed concerning the

dielectric losses and electric-field tunability below the polar phonon frequency

range. Whereas the predicted losses were much reduced compared with those of

the cores, the observed enhanced losses in the THz range give evidence of an

interdiffusion of the BaTiO3 cores into the shells.

THz and IR Dielectric Response of BaTiO3 Core–Shell Composites: Evidence for

Interdiffusion. D.Nuzhnyy, J.Petzelt, I.Rychetsky, V.Buscaglia, M.T.Buscaglia,

P.Nanni: Journal of Physics D, 2009, 42[15], 155408