Electrical and dielectrical properties of chromium doped NaCl crystals

Aggregation of Bismuth in NaCl Crystals

“…There are differences between the data reported by various authors, mainly as variations in the A-band position and the number of C-band components. Wit,h the exception of the C3-component, which we have not observed, our data are similar with those attributed by Hartmanova et al [9] to (BiO)+ centres. As will be discussed later this is rather surprising in view of the adopted crystalgrowth procedure and the aggregation property of bismuth centres.…”

“…The structural model consisting of a substitutional (BiO)+ ion, as suggested by optical spectra similar to those reported by Hartmanova et al [9] in NaCl and zu Siederdissen and Fischer [7] in KCI, does not require charge compensating vacancies, which are essential in the aggregation process. Such an assumption is supported by our observation that in bismuth-doped KC1 crystals exhibiting optical spectra attributed t o (BiO)+ centres no changes in the optical spectra were observed by thermal treatments.…”

“…Another aggregation mechanism should take into account the presence of both iv and ivv dipoles, as suggested [9] from electrical measurements on NaC1:Bi3+ crystals.…”

Spectroscopic Studies of BI3+ Centres in SrCL2 Single Crystals

“…This is probably connected with the fact that the incorporation of Bi3+ on a Sr2+ site in the crystal lattice requires the formation of charge compensating cationic vacancies.Furthermore it is known, that in some alkali halides, doped with Bi3+, BiO+ ions are formed [7]. At the high temperature of the crystal preparation (800" C) it is also possible that some Biz+ ions will be formed [5].…”

Investigations of Defect Centres in Alkali Halides Doped with Trivalent Cations. Part 1: Bismuth in NaCl, KCl and RbCl Crystals

“…Dielectric properties of trivalent cations in monovalent ionic crystals, like alkali-and silver halides, were up to now studied by various authors [1][2][3][4][5]. According to Kunze et al [5] such ions as Ti 3 +, Cr3+ and V3+ enter substitutionally the monovalent lattice of AgCl and at sufficiently low temperature are completely associated with two cation vacancies.…”