Preparation and Optical Properties of Polycrystalline Aluminum Germanate

1984 ◽  
Vol 32 ◽  
Author(s):  
S. Prochazka ◽  
G. A. Slack
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Solid Solutions ◽  
Infrared Absorption ◽  
Optical Constants ◽  
Polycrystalline Aluminum ◽  
Lattice Constants ◽  
Wide Range ◽  
Wide Compositional Range ◽  
Infrared Absorption Spectra

Aluminum germanate, the germanium analog of mullite, 3 AlO2O3 . 2 GeO2, was first prepared by Gelsdorf, Muller-Hesse and Schweite (Ref. 1), who demonstrated that both partial and complete substitution of SiO2 by GeO2 in mullite was possible. They also determined the lattice constants of the solid solutions. The following studies reported some physical properties of aluminum germanate such as density (Ref. 2) optical constants (Ref. 2) crystal structure (Ref. 3) and I. R. absorption (Ref. 4). Phase equilibria in the system AlO2O3−GeO2 were investigated by Miller et al. (Ref. 5) and Perez-y-Jorba (Ref. 6). The ratter author found several compounds of which germanium mullite was the most stable and showed a relatively wide compositional range. Miller et al. observed only 3 Al2O3 . 2 GeO2 with no evidence of solid solutions. The compound was reported to melt incongruently at 1530° C. Recently Yamaguchi et al. (Ref. 7) prepared aluminum germanates of a wide range of stoichiometry from alkyl oxides and found, in addition to germanium mullite, the compound Al2O3−2GeO2 which was stable between 1190° and 1310° C. The authors also report infrared absorption spectra.

A refinement of the dickite structure and some remarks on polymorphism in kaolin minerals

1961 ◽  
Vol 32 (252) ◽  
pp. 683-704 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Crystal Structure ◽  
Absorption Spectra ◽  
Infrared Absorption ◽  
Structural Features ◽  
Mirror Image ◽  
Hydrogen Atoms ◽  
Octahedral Layer ◽  
Layer Structures ◽  
Infrared Absorption Spectra ◽  
Interlayer Bonding

SummaryThe crystal structure of the clay mineral dickite (Al2Si2H4O9) has been refined to a greater accuracy than that reported in an earlier analysis. Improved lattiçe parameters are: a 5·15±0·001, b 8·940±0·001, c 14·424 ± 0·002Å., β 96° 44′± 1′. The dickite structure shows several significant distortions from the geometry of the idealized kaolin layer, including deformation and rotation of the silica tetra-hedra. The most striking features of the octahedral layer are the extremely short shared edges of 2·37 Å. Although the analysis was not sufficiently accurate to position the hydrogen atoms with certainty, a model consistent with the infrared absorption spectra is proposed. The stacking sequences of kaolin-layer minerals have been considered with reference to the structural features observed in dickite. There are thirty-six ways of superposing two kaolin layers commensurate with the OH-O bonds found in kaolinite, dickite, and nacrite. The twelve sequences showing the least amount of cation-cation superposition between consecutive kaolin layers can be used to construct two one-layer cells, kaolinite and its mirror image, and twelve two-layer cells, including dickite and nacrite. The distortions of the kaolin layer introduce secondary variations in the interlayer bonding that suggest that dickite and nacrite are the most stable of the kaolin layer structures, since they possess the shortest oxygen-hydroxyl contacts.

scholarly journals Broadband Optical Properties of Atomically Thin PtS2 and PtSe2

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3269
Author(s):  
Georgy A. Ermolaev ◽  
Kirill V. Voronin ◽  
Mikhail K. Tatmyshevskiy ◽  
Arslan B. Mazitov ◽  
Aleksandr S. Slavich ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Constants ◽  
Transition Metal Dichalcogenides ◽  
Optoelectronic Device ◽  
High Refractive Index ◽  
Broadband Absorption ◽  
Wide Range ◽  
Out Of Plane ◽  
Metal Dichalcogenides ◽  
Infrared Wavelengths

Noble transition metal dichalcogenides (TMDCs) such as PtS2 and PtSe2 show significant potential in a wide range of optoelectronic and photonic applications. Noble TMDCs, unlike standard TMDCs such as MoS2 and WS2, operate in the ultrawide spectral range from ultraviolet to mid-infrared wavelengths; however, their properties remain largely unexplored. Here, we measured the broadband (245–3300 nm) optical constants of ultrathin PtS2 and PtSe2 films to eliminate this gap and provide a foundation for optoelectronic device simulation. We discovered their broadband absorption and high refractive index both theoretically and experimentally. Based on first-principle calculations, we also predicted their giant out-of-plane optical anisotropy for monocrystals. As a practical illustration of the obtained optical properties, we demonstrated surface plasmon resonance biosensors with PtS2 or PtSe2 functional layers, which dramatically improves sensor sensitivity by 60 and 30%, respectively.

New Ge-Sn materials with adjustable bandgaps and lattice constants

2002 ◽  
Vol 744 ◽  
Author(s):  
Matthew R. Bauer ◽  
John Tolle ◽  
A. V. G. Chizmeshya ◽  
S. Zollner ◽  
J. Menendez ◽  
...  
Keyword(s):  
Optical Properties ◽  
Secondary Ion Mass Spectrometry ◽  
Compositional Dependence ◽  
X Ray Diffraction ◽  
Chemical Methods ◽  
Lattice Constants ◽  
New Class ◽  
Transmission Electron ◽  
Wide Range ◽  
Secondary Ion

ABSTRACTThe synthesis and optical properties of a new class of Si-based infrared semiconductors in the Ge1-x Snx system are described. Chemical methods based on deuterium-stabilized Sn hydrides and UHV-CVD were used to prepare a wide range of metastable compositions and structures directly on silicon. These materials exhibit high thermal stability, superior crystallinity, and unique crystallographic and optical properties, such as adjustable band gaps and lattice constants. These properties are characterized by Rutherford backscattering, low-energy secondary ion mass spectrometry, high-resolution transmission electron microscopy, x-ray diffraction as well as infrared and Raman spectroscopies and spectroscopic ellipsometry. The films grow essentially strain free and display a strong compositional dependence of the band structure.

Crystal structure, polarization properties and reverse nonlinearity of solid solutions of the KNN-PZT system in a wide range of external influences

2021 ◽  
Vol 47 (1) ◽  
pp. 138-148
Author(s):  
K.P. Andryushin ◽  
L.A. Shilkina ◽  
I.N. Andryushina ◽  
M.O. Moysa ◽  
D.I. Rudsky ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid Solutions ◽  
External Influences ◽  
Wide Range

Crystal Structure and Optical Properties of CoCr2O4–NiCr2O4 Solid Solutions Prepared by Low-Temperature Combustion Synthesis Method

2012 ◽  
Vol 616-618 ◽  
pp. 1877-1881 ◽  
Author(s):  
Ai Jun Han ◽  
Ming Quan Ye ◽  
Zhi Min Zhang ◽  
Juan Juan Liao ◽  
Nan Li
Keyword(s):  
Crystal Structure ◽  
Optical Properties ◽  
Low Temperature ◽  
Combustion Synthesis ◽  
Solid Solutions ◽  
Synthesis Method ◽  
Visible Region ◽  
Low Temperature Combustion ◽  
Temperature Combustion ◽  
Phase Spinel

The Co1-xNixCr2O4(x=0.1, 0.2 and 0.3) solid solutions were successfully synthesized by low-temperature combustion synthesis method. The crystal structure and optical properties of the samples were investigated. The samples displayed single phase spinel structure with 30 nm in grain size. Infrared absorption peaks at about 525 and 630 cm-1 corresponded to the vibration of octahedron group ([CrO6] / [NiO6]) and tetrahedron group ([CoO4] / [NiO4]) respectively. Due to the electronic transition of 4A2(F) → 4T1(P) of Co2+, 4A2g → 4T2g of Cr3+, 3T1g(F) → 3T1g(P) and 3A2g(F) → 3T1g(F) of Ni2+, absorption peaks at about 578, 618 and 670 nm were observed in the visible region, making the color center be green. The degree of lightness, greenness and chroma increased, whereas the degree of blueness decreased, making the color of the samples transit from pale green to brilliant green as x value increased.

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