An optical in-situ study of the re-oxidation kinetics of mixed valent Yb3Al5O12

Kreye, M.; Becker, Klaus‐Dieter

doi:10.1039/b300141p

Cited by 31 publications

(21 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In as-grown crystals and films, although, Yb 3+ -ions can be reduced to Yb 2+ -ions, which are the effective luminescence quenching centers [3]. In [2] the oxidation of blue Yb 3 Al 5 O 12 at high temperatures was studied. It is associated with the bleaching of the crystals due to the recharging process Yb 2+ ↔Yb…”

Section: +mentioning

confidence: 99%

See 1 more Smart Citation

Optical in‐situ study of the oxidation and reduction kinetics of Yb‐substituted YAG epitaxial films

Martynyuk

Ubizskii

Buryy

et al. 2005

phys. stat. sol. (c)

Self Cite

View full text Add to dashboard Cite

The optical spectra of the Yb-substituted Yb 3 Al 5 O 12 (YAG) epitaxial films and the Yb ions recharging kinetics have been investigated by means of in-situ optical spectroscopy in the temperature range between 900 and 1100°C at oxidation and reduction condition. This work continues the studies of the spectral properties of Yb:YAG epitaxial films represented in [1] and optical in-situ study of the re-oxidation kinetics of Yb 3 Al 5 O 12 (YbAG) crystal represented in [2] where the model of internal oxidation of ytterbium ions Yb 2+ → Yb 3+ in the bulk crystal was developed and proofed. The changes of the absorption spectra of Yb:YAG film during oxidation and reduction were attributed to the recharging process Yb 3+ ↔ Yb 2+. It was found that the oxidation kinetics in epitaxial films do not agree to the model [2] and do not follow a parabolic rate law in contrary to bulk YbAG single crystal.

show abstract

Section: +mentioning

confidence: 99%

“…High-temperature optical in-situ experiments were performed at 900, 1000 and 1100°C employing a specially designed high-temperature furnace. Oxidation and reduction experiments were performed in an experimental set-up that allows rapid oxygen activity jumps by means of fast gas changes (for details see [2]). …”

Section: +mentioning

confidence: 99%

Optical in‐situ study of the oxidation and reduction kinetics of Yb‐substituted YAG epitaxial films

Martynyuk

Ubizskii

Buryy

et al. 2005

phys. stat. sol. (c)

Self Cite

View full text Add to dashboard Cite

show abstract

“…In situ optical absorption spectra of the films deposited on Al 2 O 3 substrates were recorded with a Lambda-900 Spectrophotometer (Perkin Elmer) in the 250-860 nm wavelength range 26 .…”

Section: High Resolution Transmission Electron Microscopy (Hrtem) Andmentioning

confidence: 99%

A chemically driven insulator–metal transition in non-stoichiometric and amorphous gallium oxide

et al. 2008

View full text Add to dashboard Cite

Insulator-metal transitions are well known in transition metal oxides, but inducing an insulator-metal transition in the oxide of a main group element is a major challenge. Here we report the observation of an insulator-metal transition, with a conductivity jump of seven orders of magnitude, in highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO 1.2 at a temperature around 670 K. We demonstrate through experimental studies and density-functional-theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric Ga 2 O 3 within the metastable oxide matrix -in chemical terms by a disproportionation. This novel mechanism -an insulator-metal transition driven by a heterogeneous solid state reactionopens up a new route to achieve metallic behaviour in oxides that are expected to exist only as classic insulators.Insulator-metal transitions belong to the most fascinating phenomena in condensed-matter physics 1,2 . Since Mott's landmark work 3,4 it has been known that in crystalline solids strong electron-electron interactions can cause an insulator-metal transition. One example is crystalline Cr-doped vanadium oxide, (V 1-x Cr x ) 2 O 3 , which shows a Mott transition from a paramagnetic Mott insulator to a strongly correlated metal upon an increase in pressure, a lowering of temperature, or a decrease in dopant level 5,6 . In non-crystalline solids structural disorder can also lead to an insulator-metal transition on account of Anderson localization 7 .As shown by Anderson 7 and Mott 8 , in any non-crystalline material the lowest states in the conduction band are localized, i.e. they are electron traps. Only for energies above the mobility edge, E c , do states become non-localized or extended. If the Fermi energy E F is below the mobility edge, states at the Fermi level are localized and the material is an electronic insulator. If, however, the number of electrons increases and the Fermi energy rises above the mobility edge, the material becomes metallic (Anderson transition). As transition metals change their valence state easily, most examples of insulator-metal transitions concern transition metal compounds 4-6,9-11 . The above considerations do not, however, exclude the possibility of inducing an insulator-metal transition in a simple binary oxide of a main group element, even without doping. Instead, large deviations from the ideal stoichiometry, i.e. high defect concentrations, provide a high concentration of electronic defects (self-doping). And if, in addition, the oxide is amorphous, there are two phenomena, strong structural disorder and strong chemical disorder, which could result in an insulator-metal transition.Here we report such a case: Highly non-stoichiometric, amorphous gallium oxide with an approximate chemical composition GaO 1.2 shows an unprecedented insulator-metal transition, with a jump in conductivity of ca. 7 orders of magnitude at temperatures as high as 670 K. We show that this in...

show abstract

“…9 The absorption at longer wavelengths which becomes visible at higher Yb contents may be caused by intervalence charge transfer (IVCT) between Yb 2+ and Yb 3+ . 25 Although the reflection shows the presence of a substantial amount of Yb 2+ , no Yb 2+ emission could be generated by excitation in the observed bands. The lack of Yb 2+ emission is either the result of strong temperature quenching which is a common problem in Yb-doped materials, 16 or by absorption by the IVCT process.…”

Section: Optical Properties Of the Yb-glassesmentioning

confidence: 93%