Vanadium characterization in BTO: V sillenite crystals

Abstract

Visible and Infrared Optical Absorption and Electron Paramagnetic Resonance (EPR) techniques have been used to characterize the intrinsic defects in sillenite type crystals: nominally pure Bi12TiO20 (BTO) and doped with vanadium (BTO:V). Optical quality crystals, with the composition Bi12.04±0.08Ti0.76±0.07V0.16±0.02O20, have been grown. Results obtained by these different techniques have shown unambiguously the 5+ valence state of the vanadium ion in BTO:V crystals. In pure BTO samples, the EPR and optical spectra show strong evidence of the presence of the intrinsic defect BiM3+ + ho+, which consists of a hole h+, mainly located on the oxygen neighbors of the tetrahedrally coordinated Bi3+ ion. After doping with vanadium, results have shown that the characteristic bands, associated to this hole defect center, disappear, suggesting its transformation in single Bi3+. Anisotropy of the EPR spectra , at 20 K, is related to Fe3+ impurities

Atomistic simulation and XAS investigation of Mn induced defects in Bi12TiO20

“…Mn is more conductive than the pure sample for all temperatures tested, and that at higher temperatures this effect is more evident. It was reported in the literature that dark conductivity in BTO host is p-type, associated to antisite defect with charge compensation by trapped holes (Bi´T i +h • ) [7]. This defect is considered the acceptor centre responsible for electrical dark conduction [11].…”

“…The combination of electro-optical and photoconductivity properties results in the so-called photorefractive effect [7,8]. Due to these properties, sillenite crystals are useful for many advanced and promising applications, such as a reversible recording medium for real-time holography, image processing applications, coherent light amplification, optical phase conjugation, optical information processing, optical interconnection and communications [7,9].…”

“…Bismuth titanium oxide crystals, Bi 12 TiO 20 (BTO), have some practical advantages compared to their isomorphs Bi 12 SiO 20 (BSO) and Bi 12 GeO 20 (BGO), including lower optical activity, larger electro-optic and photoconductivity coefficients and higher sensitivity to red light [7]. As with most photorefractive materials, BTO presents a rich defect structure, the nature of which is still a matter of active research.…”

Fabrication and Electrical Characterization of Translucent Bi12TiO20Ceramics

“…surf , possibly favoring conduction by oxygen migration [21]. On the other hand, EPR measurements indicated the presence of hole centers in BTO, possibly arising from antisite defects Bi Ti + ℎ • [22], which would result in electronic ptype conduction. According to our results, both hypotheses are plausible, but the remarkable fact is that = 0.99 eV determined for high density of BTO ceramics is the same as reported previously for single crystals [4].…”

Electrical and Dielectric Characterization of Bi12GeO20Prepared by Modified Pechini Method

“…Bismuth germanate (Bi 12 GeO 20 ) belongs to a class of materials known as sillenites with general formula Bi 12 MO 20 , where M represents a tetravalent ion or a combination of ions yielding average charge 4+ [1,2]. Sillenites crystallize in the cubic system (space group I23) and usually present photorefractive and electrooptical properties [3][4][5] that make them useful as recording media, optical switching, and sensors, among others [6][7][8][9]. For optical applications, transparency and crystalline coherence are required, so the devices employ single crystals.…”