Electrical properties of semiconducting (1−x)(90V2O5–10P2O5)+xBaTiO3 glass and glass–ceramics

Abstract

Homogeneous (1−x)(90V2O5–10P2O5)+x(BaTiO3) glasses (abbreviated as VPBT) are formed with lower concentrations (x) of BaTiO3 (x<0.3). For x>0.3 microcrystallization of BaTiO3 appears during glass formation (corresponding samples are termed as glass–ceramics). All of these oxide glasses show semiconducting behavior. Electrical conductivity data measured between 80 and 450 K follow the adiabatic small polaron hopping conduction mechanism for glasses with lower concentrations (x<0.2), but for higher concentrations of BaTiO3 (x>0.2) the said conduction mechanism is changed to the nonadiabatic regime. Low temperature (T≤150 K) conductivity data of these glass samples can be well fitted with the variable range hopping model. At higher temperatures, Mott’s model of phonon assisted small polaron hopping between nearest neighbors is consistent with the conductivity data. The polaron hopping model of Schnakenberg can predict the conductivity data in the entire temperature range of measurement. However, the percolation model, valid for the similar V2O5–Bi2O3+SrTiO3 glass (denoted by VBBT), is not consistent with the experimental results of VPBT glass samples. Again the frequency dependent ac conductivity data of the VPBT glasses follow overlapping large polaron hopping model, while those of the VBBT glasses satisfy the correlated barrier hopping model.