Sol-gel processing of lithium niobate thin layers for optical applications

1990 ◽  
Author(s):  
Dennis J. Eichorst ◽  
David A. Payne
Keyword(s):  
Lithium Niobate ◽  
Sol Gel ◽  
Thin Layers ◽  
Optical Applications ◽  
Gel Processing

scholarly journals Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

2020 ◽  
Author(s):  
Christiane Adler ◽  
Igor Krivtsov ◽  
Dariusz Mitoraj ◽  
Lucía dos Santos-Gómez ◽  
Santiago García-Granda ◽  
...  
Keyword(s):  
Soft Matter ◽  
High Performance ◽  
Carbon Nitride ◽  
Sol Gel ◽  
Thin Layers ◽  
Water Soluble ◽  
New Paradigm ◽  
High Quality ◽  
Free Films ◽  
Gel Processing

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for photoelectrochemical (PEC) applications, the fabrication of high-quality PCN photoelectrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of photoanodes based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor composed of nanosized (~10 nm) particles that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on a conductive substrate resulting in formation of mechanically stable porous polymeric thin layers (~400 nm), in contrast to the commonly obtained loosely attached thick particulate coatings. The resulting photoanodes exhibit unprecedented PEC performance in methanol reforming in neutral pH electrolytes with photocurrents of up to 177±27 mA cm<sup>-2</sup> (1 sun illumination) and 320±40 mA cm<sup>-2</sup> (2 sun illumination) at 1.23 V vs. RHE, maintaining such high photocurrents even down to ~0 V vs. RHE. These parameters permit effective operation even without any external electric bias, as demonstrated by bias-free photoreforming of methanol and glycerol, and highly selective (~100%) photooxidation of 4-methoxybenzyl alcohol (4-MBA). The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems, and pave the way for further applications in which high-quality PCN films are required.

Chemical Processing and Properties of Nanocrystalline BaTiO3

1992 ◽  
Vol 271 ◽  
Author(s):  
Z. Xu ◽  
H. K. Chae ◽  
M. H. Frey ◽  
D. A. Payne
Keyword(s):  
Grain Size ◽  
Thermal Processing ◽  
Room Temperature ◽  
Sol Gel ◽  
Thin Layers ◽  
Silicon Substrates ◽  
Chemical Processing ◽  
Temperature Structure ◽  
Processing Conditions ◽  
Gel Processing

ABSTRACTBarium titanate (BaTiO3) thin layers were prepared by sol-gel processing. Details are reported for the synthesis route from methoxyethoxide precursors. Partially hydrolyzed solutions were spin-cast onto metallized silicon substrates, and a multilayering technique was used to develop sub-micron structures. Information is reported on the thermal processing conditions used and the development of structure. Crystallization started at 600°C and was fully developed by 700°C. The room temperature structure was cubic, and the grain size was 25–50 nm. Details are reported for the dielectric properties. Ferroelectricity was not observed. Dielectric constant (200–300) increased with increasing grain size, and was stable with respect to temperature, field and frequency. The properties are attractive for potential integrated capacitor applications.

Evolution Of Molecular Structure In Alkoxide-Derived Lithium Niobate

1990 ◽  
Vol 180 ◽  
Author(s):  
Dennis J. Eichorst ◽  
D. A. Payne
Keyword(s):  
Heat Treatment ◽  
Lithium Niobate ◽  
Structural Changes ◽  
Sol Gel ◽  
Lithium Oxide ◽  
Structural Rearrangements ◽  
Raman Spectroscopic ◽  
Amorphous Network ◽  
Niobium Ethoxide ◽  
Gel Processing

ABSTRACTStructural rearrangements during the sol-gel processing of lithium niobate were investigated by FTlR and Raman spectroscopic methods. The reaction of lithium ethoxide with niobium ethoxide resulted in the formation of a bimetallic alkoxide, LiNb(OEt)6 , which could be crystallized from solution. Single crystals were comprised of helical polymeric units consisting of niobium octahedra linked by lithium in tetrahedral (distorted) coordination. Successive crystallizations from solution allowed for the enhanced purification of the alkoxide precursor. Hydrolysis of the bimetallic alkoxide resulted in the formation of an amorphous network structure, which contained niobium-oxygen octahedral units modified by lithium. Heat-treatment facilitated structural rearrangements for the niobium environment, which allowed for the formation of the lithium niobate crystal structure. Further heat-treatment above 700°C resulted in structural changes associated with lithium oxide volatility.

scholarly journals Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

2020 ◽  
Author(s):  
Christiane Adler ◽  
Igor Krivtsov ◽  
Dariusz Mitoraj ◽  
Lucía dos Santos-Gómez ◽  
Santiago García-Granda ◽  
...  
Keyword(s):  
Soft Matter ◽  
High Performance ◽  
Carbon Nitride ◽  
Sol Gel ◽  
Thin Layers ◽  
Water Soluble ◽  
New Paradigm ◽  
High Quality ◽  
Binder Free ◽  
Gel Processing

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for various applications, the fabrication of high-quality, binder-free PCN films and electrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of thin films based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on conductive substrates resulting in formation of mechanically stable polymeric thin layers. The resulting photoanodes exhibit unprecedented PEC performance in alcohol reforming and selective (~100%) conversions with very high photocurrents down to ~0 V vs. RHE, which enables even effective operation under bias-free conditions. The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems, and pave the way for further applications in which high-quality PCN films are required.

Crystallization Behavior of Chemically Synthesized LiNbO3

1991 ◽  
Vol 49 ◽  
pp. 964-965
Author(s):  
Vikram Joshi
Keyword(s):  
Lithium Niobate ◽  
Crystallization Behavior ◽  
Sol Gel ◽  
Stoichiometric Composition ◽  
Lithium Carbonate ◽  
Processing Technique ◽  
Homogeneous Material ◽  
Precise Control ◽  
Oxide Powders ◽  
Optical Applications

Lithium niobate is a material of interest for electro-optic and nonlinear optical applications. Conventional processing of lithium niobate involves the relatively coarse scale of mixing of lithium carbonate and niobium oxide powders, which makes it difficult to obtain a chemically homogeneous, single phase product. In recent years, sol-gel processing of lithium niobate has been investigated as a method of producing high purity, homogeneous material of stoichiometric composition. This processing technique permits easy and precise control over composition, intimate mixing of the constituent elements, and the use of relatively low processing temperatures. This present study investigates the crystallization behavior of gels formed by the hydrolysis of mixed alkoxides of lithium and niobium in low molecular weight alcohols. Crystallization was found to be initiated at temperatures as low as 200°C and could be completed by 450°C.

Sol-Gel Processing of Lithium Niobate Thin-Layers on Silicon

1988 ◽  
Vol 121 ◽  
Author(s):  
Dennis J. Eichorst ◽  
D. A. Payne
Keyword(s):  
Sol Gel ◽  
Solution Chemistry ◽  
Thin Layers ◽  
Processing Route ◽  
High Quality ◽  
Spin Casting ◽  
Evolution Of Structure ◽  
Stable Solutions ◽  
Gel Processing

ABSTRACTSol-gel processing was used for the fabrication of LiNbO3 thin-layers on semiconductors. Two different alkoxide systems were investigated (i.e., ethoxide vs. methoxyethoxide) to determine the role of solution chemistry on the evolution of structure in LiNbO3 layers. An alcohol exchange reaction, which produced lithium niobium methoxyethoxide, proved advantageous with respect to the amount of hydrolysis water content which could be added to give stable solutions. Spin-casting was used for the deposition of thin-layers which crystallized at 500 C on Si. The refractive index of sol-gel derived LiNbO3 was determined to be similar to sputtered or epitaxially grown films. Data are reported for the processing route and the material characteristics. Methoxyethanol based systems appeared to be more forgiving than ethanol based solutions for the fabrication of high-quality thin-layer devices.

Aryl-Bridged Polysilsesquioxanes - New Microporous Materials.

1990 ◽  
Vol 180 ◽  
Author(s):  
Kenneth J. Shea ◽  
Owen Webster ◽  
Douglas A. Loy
Keyword(s):  
High Surface ◽  
Sol Gel ◽  
Refractive Indices ◽  
Surface Areas ◽  
New Family ◽  
Rigid Rod ◽  
Optical Applications ◽  
Degree Of Condensation ◽  
Gel Processing ◽  
Thermal Stability Of

ABSTRACTThe first representatives of a new family of microporous, aryl-bridged polysilsesquioxanes have been prepared by sol-gel processing of bis-1,4-(triethoxysilyl)benzene la, bis-4,4′- (triethoxysilyl)biphenyl 2a, bis-4,4′-(triethoxysilyl)terphenyl 3a, and bis-9,10-triethoxysilyl anthracene 4a. The bis(trichlorosilyl) analogs of la and 2a (lb and 2b, respectively) were also examined. The materials produced by hydrolysis and condensation of the monomers provide an opportunity to fully condense to a network with rigid-rod organic spacers interspaced at regular intervals in the silicate-like framework. The xerogels produced upon subsesquent processing of the gels have extremely high surface areas (256–1100 m2/g; BET) with porosities confined to the micropore domain (< 200 nm). Solid state (CP MAS) 13C and 29Si NMR were used to evaluate the extent of hydrolysis and degree of condensation in the xerogels. The porosity and thermal stability of the aryl bridged polysilsesquioxanes may lead to applications as chromatographic absorbents. The transparent materials may also have optical applications arising from both the gels′ high refractive indices and the covalent incorporation of ultraviolet chromophores.

scholarly journals Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

2020 ◽  
Author(s):  
Christiane Adler ◽  
Igor Krivtsov ◽  
Dariusz Mitoraj ◽  
Lucía dos Santos-Gómez ◽  
Santiago García-Granda ◽  
...  
Keyword(s):  
Soft Matter ◽  
High Performance ◽  
Carbon Nitride ◽  
Sol Gel ◽  
Thin Layers ◽  
Water Soluble ◽  
New Paradigm ◽  
High Quality ◽  
Binder Free ◽  
Gel Processing

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for various applications, the fabrication of high-quality, binder-free PCN films and electrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of thin films based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on conductive substrates resulting in formation of mechanically stable polymeric thin layers. The resulting photoanodes exhibit unprecedented PEC performance in alcohol reforming and selective (~100%) conversions with very high photocurrents down to ~0 V vs. RHE, which enables even effective operation under bias-free conditions. The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems, and pave the way for further applications in which high-quality PCN films are required.

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