AC conductivity of doped Bi12SiO20 crystals

Crystals of Bi12SiO20 doped with Al, P, Fe, Cr, Mn and Ni have been grown u sing the Czochralski method. The real and imaginary parts of AC conductivit y have been measured in the temperature range 300-600 It and in the frequen cy range 10(4)-10(3) s(-1). From the analysis of the frequency and temperat ure dependencies of conductivity, we have concluded that the relevant AC tr ansport is due to hopping of carriers between defect sites. The activation energies at frequency 10(4) s(-1) for crystals doped with different impurit ies is in the range 0.4-1.6 eV. The imaginary part of the conductivity for all samples has linear frequency dependence in the whole temperature range. For the samples doped with transition metal impurities it is one to three orders of magnitude greater compared to the real part. In samples doped wit h P and Al, both parts of conductivity become equal at about 450 K. (C) 200 0 Elsevier Science S.A. All rights reserved.