ANOMALIES OF PHYSICAL-PROPERTIES IN ALPHA-BI2O3 - A PHASE-TRANSITION GOVERNED BY THE ELECTRONIC MECHANISM

A number of physical properties of alpha-Bi2O3 was studied: the therma l expansion, thermally stimulated conductivity, electrical resistivity , and dielectric permeability. X-ray diffraction, DTA, and differentia l scanning calorimetry measurements were also carried out. Several ano malies were observed: a small maximum and drastic rise of the single c rystal dielectric permeability, a sharp drop of the electric resistivi ty, a jump and change in sign Of the thermally stimulated current, and an exothermal maximum an differential heat capacity. At the same time , the monoclinic lattice symmetry of alpha-Bi2O3 was retained over the temperature range where these anomalies were found.