AC conductivity of doped Bi12SiO20 crystals

Crystals of Bi12SiO20 doped with Al, P, Fe, Cr, Mn and Ni have been grown using the Czochralski method. The real and imaginary parts of AC conductivity have been measured in the temperature range 300-600 It and in the frequency range 10(4)-10(3) s(-1). From the analysis of the frequency and temperature dependencies of conductivity, we have concluded that the relevant AC transport is due to hopping of carriers between defect sites. The activation energies at frequency 10(4) s(-1) for crystals doped with different impurities 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 with P and Al, both parts of conductivity become equal at about 450 K. (C) 2000 Elsevier Science S.A. All rights reserved.