Details
| Original language | English |
|---|---|
| Pages (from-to) | 51-61 |
| Number of pages | 11 |
| Journal | Journal of alloys and compounds |
| Volume | 246 |
| Issue number | 1-2 |
| Publication status | Published - 15 Jan 1997 |
Abstract
Attempts have been made to grow crystals of alkali metal hexagonal (HTB) and tetragonal (TTB) tungsten bronzes (MxWO3) by chemical transport in a temperature gradient. Different transport agents were used (HgCl2, HgBr2, HgI2, Cl2, PtCl2). Needle-shaped crystals of up to 6 mm in length could be grown using only HgCl2 and HgBr2. It was observed that the size of HTB crystals and the transport rate drop with increasing content of alkali metal. TTB crystals larger than 0.1 mm in dimensions could not be prepared. The electrical properties of different crystals have been investigated by reflection spectroscopy in the spectral range from 600 to 20 000 cm-1. The spectral properties can be explained by using the Drude free carrier model. According to this there are plasma frequencies which are shifted systematically towards larger values for larger x, and anisotropic effective masses m*(E⊥) ≈ 3m*(E∥c) with m*(E⊥c) between 0.5 and 1.3 which also increase systematically with respect to x. An exclusion from Drude behaviour is observed for K-HTB for the E∥c polarization. For these cases the line profile can better be described using a Lorentz-oscillator model.
Keywords
- Alkali tungsten bronzes, Crystal growth, Drude free carrier behaviour, Optical properties, Plasma frequencies
ASJC Scopus subject areas
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
- Materials Science(all)
- Metals and Alloys
- Materials Science(all)
- Materials Chemistry
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In: Journal of alloys and compounds, Vol. 246, No. 1-2, 15.01.1997, p. 51-61.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Crystal growth of alkali metal tungsten bronzes MxWO3 (M = K, RB, Cs), and their optical properties
AU - Hussain, A.
AU - Gruehn, R.
AU - Rüscher, C. H.
N1 - Funding Information: 4.H. is grateful to the Alexander van Humboldt-Stiftung for financial suppmt with a research fellowship for his stay in Gi&n and Hannover and to the SFB I73 for additional support to this work in Hannover. The generous support of research performed in the laboratory in GieDen by the Deutsche Forschuttgagemeinschaf(tS PP 322456) and the “Fends der Chemischzn industrie” are gratefully acknowledged.
PY - 1997/1/15
Y1 - 1997/1/15
N2 - Attempts have been made to grow crystals of alkali metal hexagonal (HTB) and tetragonal (TTB) tungsten bronzes (MxWO3) by chemical transport in a temperature gradient. Different transport agents were used (HgCl2, HgBr2, HgI2, Cl2, PtCl2). Needle-shaped crystals of up to 6 mm in length could be grown using only HgCl2 and HgBr2. It was observed that the size of HTB crystals and the transport rate drop with increasing content of alkali metal. TTB crystals larger than 0.1 mm in dimensions could not be prepared. The electrical properties of different crystals have been investigated by reflection spectroscopy in the spectral range from 600 to 20 000 cm-1. The spectral properties can be explained by using the Drude free carrier model. According to this there are plasma frequencies which are shifted systematically towards larger values for larger x, and anisotropic effective masses m*(E⊥) ≈ 3m*(E∥c) with m*(E⊥c) between 0.5 and 1.3 which also increase systematically with respect to x. An exclusion from Drude behaviour is observed for K-HTB for the E∥c polarization. For these cases the line profile can better be described using a Lorentz-oscillator model.
AB - Attempts have been made to grow crystals of alkali metal hexagonal (HTB) and tetragonal (TTB) tungsten bronzes (MxWO3) by chemical transport in a temperature gradient. Different transport agents were used (HgCl2, HgBr2, HgI2, Cl2, PtCl2). Needle-shaped crystals of up to 6 mm in length could be grown using only HgCl2 and HgBr2. It was observed that the size of HTB crystals and the transport rate drop with increasing content of alkali metal. TTB crystals larger than 0.1 mm in dimensions could not be prepared. The electrical properties of different crystals have been investigated by reflection spectroscopy in the spectral range from 600 to 20 000 cm-1. The spectral properties can be explained by using the Drude free carrier model. According to this there are plasma frequencies which are shifted systematically towards larger values for larger x, and anisotropic effective masses m*(E⊥) ≈ 3m*(E∥c) with m*(E⊥c) between 0.5 and 1.3 which also increase systematically with respect to x. An exclusion from Drude behaviour is observed for K-HTB for the E∥c polarization. For these cases the line profile can better be described using a Lorentz-oscillator model.
KW - Alkali tungsten bronzes
KW - Crystal growth
KW - Drude free carrier behaviour
KW - Optical properties
KW - Plasma frequencies
UR - http://www.scopus.com/inward/record.url?scp=0030677044&partnerID=8YFLogxK
U2 - 10.1016/S0925-8388(96)02470-X
DO - 10.1016/S0925-8388(96)02470-X
M3 - Article
AN - SCOPUS:0030677044
VL - 246
SP - 51
EP - 61
JO - Journal of alloys and compounds
JF - Journal of alloys and compounds
SN - 0925-8388
IS - 1-2
ER -