NONLINEAR PHYSICAL-PROPERTIES OF SOME NONCONVENTIONAL SEMICONDUCTING BI-PB-BA-O GLASSES

Semiconducting Bi1-xPbxBaO3-delta (or BPB) glasses with x = 0 to 0.8 h ave been prepared by fast quenching from the melt. Interesting anomali es in the temperature-dependent polaronic conductivity and dielectric constant have been observed in all these glass compositions at tempera tures, T-p, varying from 310 to 330 K (depending on Pb concentration). This nonlinear behavior is considered to be associated with the local ordering or the displacements of the BiO3 type pyramidal structural u nits present in the glass matrix (observed from the infrared spectra o f these glasses). This type of ordering/displacement gives rise to a l ocal instability in the glass network structure which is also supporte d by the observed heat capacity anomaly around the same temperatures T -p.