Coloring of Bi4Ge3O12 – Mn crystals induced by electric field
The effect of the direct electric field on the optical transmittance of Bi4Ge3O12 single crystals doped with Mn is studied in the mode of using asymmetric contacts when only one electrode (Ag or In-Ga) is injected. It is found that changes in the optical transmittance spectra under the action of unipolar injection of electrons and holes are different. They also differ from the case of using symmetrical electrodes (double injection mode). The optimal temperature and field conditions for electrochromic coloring are determined from the correspondence between the manifestations of the electrochromic effect in Bi4Ge3O12 ─ Mn crystals and the current-voltage characteristics. It is shown that the maximum effect is achieved by injecting holes into a Bi4Ge3O12 ─ Mn sample annealed in a reducing atmosphere.