Densification and Evolution of Stress Development in Solution Derived PbZr0.53Ti0.47O3 Thin Layers

1999 ◽  
Vol 596 ◽  
Author(s):  
Sang M. Park
Keyword(s):  
Sol Gel ◽  
Film Plane ◽  
Thin Layers ◽  
Silicon Substrates ◽  
Sintering Process ◽  
Stress Development ◽  
Insertion Method ◽  
Gel Processing ◽  
Reflectance Measurements

AbstractStress development in thin layers of PbZr0.53Ti0.47O3 (PZT) and PbTiO3 (PT) prepared by sol-gel processing was monitored by in situ laser reflectance measurements. Layers were spin coated onto silicon substrates and thermally cycled to 600°C and 650°C. The shrinkage normal to the film plane was determined by in situ ellipsometry and scanning electron microscopy. Both PZT and PT multilayers showed a similar stress behavior on heating, but quite different behavior on cooling. As the film became dense at high temperatures, total stress was dominated by the thermal expansion mismatch between the oxide layer and the substrate. On cooling, the PT multilayers, which already crystallized into the perovskite structure, ended nearly stress free at room temperature, whereas mostly amorphous PZT multilayers were under a high tensile stress. Densification in PZT layers appeared to occur between 370°C and 520°C. At near 370°C the shrinkage mode for a single PZT layer was also observed to change substantially. A two-stage sintering process employing 450°C-sintering and 650°C-crystallization was found to be as effective as direct furnace insertion method in producing a dense film.

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.

Stress Development in Low Dielectric Constant Silica Films During Drying and Heating Process

1999 ◽  
Vol 594 ◽  
Author(s):  
Mengcheng Lu ◽  
C. Jeffrey Brinker
Keyword(s):  
Dielectric Constant ◽  
Tensile Stress ◽  
Sol Gel ◽  
Low Dielectric Constant ◽  
Heating Process ◽  
Residual Tensile Stress ◽  
Silica Films ◽  
Stress Development ◽  
Low Dielectric

AbstractLow dielectric constant silica films are made using a surfactant templated sol-gel process (K∼2.5) or an ambient temperature and pressure aerogel process (K∼1.5). This paper will present the in-situ measurement and analysis of stress development during the making of these films, from the onset of drying till the end of heating. The drying stress is measured by a cantilever beam technique; the thermal stress is measured by monitoring the wafer curvature using a laser deflection method. During the course of drying, the surfactant templated films experience a low drying stress due to the influence of the surfactant on surface tension and extent of siloxane condensation. The aerogel films first develop a biaxial tensile stress due to solidification and initial drying. At the final stage of drying where the drying stress vanishes, dilation of the film recreates the porosity of the wet gel state, reducing the residual stress to zero. For the surfactant templated films, very small residual tensile stress remains after the heat treatment is finished (∼30MPa). Aerogel film has almost no measurable stress developed in the calcination process. In situ spectroscopic ellipsometry analysis during drying and heating, and TGA/DTA are all used to help understand the stress development.

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.

Sol-Gel Processing of Optical Fiber

1986 ◽  
Vol 88 ◽  
Author(s):  
M. E. Elias ◽  
A. M. Elias
Keyword(s):  
Optical Fiber ◽  
Transmission Loss ◽  
Amorphous Material ◽  
Sol Gel ◽  
Sintering Process ◽  
Exponential Time ◽  
Fiber Production ◽  
Hydrolytic Polycondensation ◽  
Gel Processing ◽  
Solid Glass

ABSTRACTA new method for optical fiber production is shown. Hydrolytic polycondensation of tetramethoxysilane using a low concentration of α-picoline, 1.56×10−3% in water, gives SiO2 gel which was dried at 22 °C to a transparent amorphous material.The densification process shows an exponential time dependence with a final value of 2.253 g/cm3 after 30 days. The specific surface area of the porous gel varies from 500 to 600 m2/g but pores are eliminated by the sintering process. Before sintering the gel, it is treated under an oxidizing atmosphere above 700 °C. At 1200 °C the pores are eliminated and a solid glass rod obtained.After the sintering process a fiber is obtained from the rod which shows a transmission loss as low as 5.5 dB/km at 840nm.

Integrated electroceramics: densification and stress development in sol-gel derived thin layers

1997 ◽  
Vol 14 (1-4) ◽  
pp. 193-200 ◽  
Author(s):  
Samit S. Sengupta ◽  
Sang M. Park ◽  
David A. Payne
Keyword(s):  
Sol Gel ◽  
Thin Layers ◽  
Stress Development

Dense and optical transparent CdWO4 films by sol-gel processing for scintillation applications

2007 ◽  
Vol 22 (6) ◽  
pp. 1527-1536 ◽  
Author(s):  
H.M. Shang ◽  
M. Bliss ◽  
S. Heald ◽  
T.K. Sham ◽  
F. Heigl ◽  
...  
Keyword(s):  
Sol Gel ◽  
Tungstic Acid ◽  
Cadmium Nitrate ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optical Luminescence ◽  
Optically Transparent ◽  
Rapid Sintering ◽  
Gel Processing

In this paper, we report the first successful fabrication of dense and optically transparent cadmium tungstate (CWO) films by sol-gel processing and the study of their optical and x-ray scintillation properties. A new sol-gel processing method was developed using tungstic acid and cadmium nitrate as precursors and hydrogen peroxide as solvent; homogeneous and stable CWO sols were aged at room temperature and used for the preparation of CWO films. A rapid sintering process was investigated and found to be necessary to make dense and optically transparent nanocrystalline CWO films. CWO films were uniform, fully dense, and crack-free, with CWO as the only detectable crystalline phase, as determined by x-ray diffraction. The thickness, density, grain size, and crystallinity of CWO films are all found to be strongly dependent on the sintering conditions and in turn impact the optical and x-ray scintillation properties. Sol-gel-derived dense CWO films demonstrated intense photoluminescence and x-ray excited optical luminescence intensity. The relationships between sol-gel processing, nanostructures, and optical and x-ray scintillation properties are discussed in detail.

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.

Origins and evolution of stress development in sol-gel derived thin layers and multideposited coatings of lead titanate

1998 ◽  
Vol 83 (4) ◽  
pp. 2291-2296 ◽  
Author(s):  
S. S. Sengupta ◽  
S. M. Park ◽  
D. A. Payne ◽  
L. H. Allen
Keyword(s):  
Lead Titanate ◽  
Sol Gel ◽  
Thin Layers ◽  
Stress Development
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