Properties of Pure and Doped Bi12GeO2oand Bi12SiO20 Crystals

Abstract

Bi12GeO20 (BGO) and Bi12SiO20 (BSO) single crystals doped with Al, Ga, P, Pb, Or, Nd, Zn, Fe, and Eu are grown from the melt in good optical quality. The segregation coefficients of the dopants range from 0.1 to 5. The undoped crystals are yellow; Al, Ga, and P bleach the crystals and increase their dark conductivity. The bleaching of these Bi12MO20 crystals can be explained by assuming a transformation of the absorption center (Bi + h) to B3+M with dopant P, and to B3+M with dopants Ga or Al. The photoconductive behavior, thermally stimulated currents, photolumines-cence at T = 1.3K, thermal expansion, heat capacity, and breaking strength of these crystals are also determined.