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.

Sol-gel processing of cordierite: Effect of seeding and optimization of heat treatment

1990 ◽  
Vol 5 (5) ◽  
pp. 1095-1103 ◽  
Author(s):  
Ann M. Kazakos ◽  
Sridhar Komarneni ◽  
Rustum Roy
Keyword(s):  
Heat Treatment ◽  
Single Phase ◽  
Excess Free Energy ◽  
Sol Gel ◽  
Nucleating Agents ◽  
Optimum Conditions ◽  
Nanosized Powders ◽  
Nanocomposite Gels ◽  
Powder Compacts ◽  
Gel Processing

Three series of cordierite powders were prepared by the sol-gel route: a single phase (monophasic) gel prepared from alkoxides, a nominally triphasic nanocomposite gel made with two nanosized powders and one solution phase, and a truly compositionally triphasic nanocomposite gel prepared from three nanosized powders. Crystalline α-cordierite seeds were also incorporated with the gels and their effectiveness as nucleating agents was investigated and found to lower the crystallization temperature of α-cordierite by 125–150°C. The densification behavior of powder compacts was examined and alterations made to the heat treatment until optimum conditions were found. The truly triphasic compact sintered at 1300°C for 2 h resulted in 100% of theoretical density whereas the nominally triphasic and monophasis pellets densified to 96% and 80%, respectively. The enhanced densification achieved with powder compacct prepared for triphasic nanocomposite gels is due to part to the excess free energy of the three components.

Phase Transformations in Sol-Gel PZT Thin Films

2000 ◽  
Vol 623 ◽  
Author(s):  
D.P. Eakin ◽  
M.G. Norton ◽  
D.F. Bahr
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Room Temperature ◽  
Structural Changes ◽  
Sol Gel ◽  
Ex Situ ◽  
Ambient Conditions ◽  
Crystalline Films ◽  
In Situ Heating

AbstractThin films of PZT were deposited onto platinized and bare single crystal NaCl using spin coating and sol-gel precursors. These films were then analyzed using in situ heating in a transmission electron microscope. The results of in situ heating are compared with those of an ex situ heat treatment in a standard furnace, mimicking the heat treatment given to entire wafers of these materials for use in MEMS and ferroelectric applications. Films are shown to transform from amorphous to nanocrystalline over the course of days when held at room temperature. While chemical variations are found between films crystallized in ambient conditions and films crystallized in the vacuum conditions of the microscope, the resulting crystal structures appear to be insensitive to these differences. Significant changes in crystal structure are found at 500°C, primarily the change from largely amorphous to the beginnings of clearly crystalline films. Crystallization does occur over the course of weeks at room temperature in these films. Structural changes are more modest in these films when heated in the TEM then those observed on actual wafers. The presence of Pt significantly influences both the resulting structure and morphology in both in situ and ex situ heated films. Without Pt present, the films appear to form small, 10 nm grains consisting of both cubic and tetragonal phases, whereas in the case of the Pt larger, 100 nm grains of a tetragonal phase are formed.

Synthesis and Dielectric Properties of SrBi2Nb2O9 Layered Perovskite by Sol-Gel Processing

1998 ◽  
Vol 541 ◽  
Author(s):  
Y. Wu ◽  
F. S. Ohuchi ◽  
G. Z. Cao
Keyword(s):  
Heat Treatment ◽  
Sol Gel ◽  
Dip Coating ◽  
Dielectric Constants ◽  
Layered Perovskite ◽  
Condensation Process ◽  
Complexing Agent ◽  
Low Dielectric ◽  
Gel Processing ◽  
Multiple Step

AbstractFerroelectric layered perovskite strontium bismuth niobium oxide SrBi2Nb2O9(SBN) ceramics and films were made by sol-gel processing. A multiple step hydrolysis-condensation process was applied to the synthesis of the SBN sol by using inorganic salts as precursors with citric acid as a complexing agent. Single phase polycrystalline SBN was obtained after heat-treatment at 650°C. It was found that the dielectric constants of SBN ceramics were dependent on heat-treatment. SEM, XPS, TGA/DTA and XRD analyses indicated that bismuth-deficiency may contribute to the relatively low dielectric constants. While a prolonged firing time at high temperatures may lead to a lattice expansion resulting in a significant decrease of the dielectric constant. C-oriented SBN films were obtained by dip-coating onto SrTiO3 substrates and the films are dense and crack-free with a thickness of 900 nm.

Sol-gel processing of PbTiO3 and Pb(Zr0.52Ti0.48)O3 fibers

1992 ◽  
Vol 7 (4) ◽  
pp. 992-996 ◽  
Author(s):  
Ulagaraj Selvaraj ◽  
A.V. Prasadarao ◽  
Sridhar Komarneni ◽  
Keith Brooks ◽  
Stewart Kurtz
Keyword(s):  
Heat Treatment ◽  
Sol Gel ◽  
Dielectric Constants ◽  
Heat Treated ◽  
Viscous Solutions ◽  
Gel Processing ◽  
Alkoxide Precursors

Homogeneous and stoichiometric PbTiO3 and PbZr0.52Ti0.48O3 gel fibers were drawn from viscous solutions prepared by sol-gel processing of alkoxide precursors. The fibrous gels on heating at 450 and 600 °C, respectively, formed the well-crystallized phases of PbTiO3 and PbZr0.52Ti0.48O3. Fibers heat treated at 700 °C are a few centimeters long and 50 to 150 μm in diameter. PbZr0.52Ti0.48O3 fibers subjected to heat treatment at 700 °C for 1 h consisted of fully dense submicron grains (0.15 to 0.2 μm). However, PbTiO3 fibers under analogous conditions showed a few micropores with grains of ∼0.1 μm. Dielectric constants of these PbTiO3 and PbZr0.52Ti0.48O3 fibers were approximately 300 and 800, respectively.

Raman spectroscopic analysis of the sol-gel processing of mixtures

1997 ◽  
Vol 410-411 ◽  
pp. 157-160 ◽  
Author(s):  
B. Riegel ◽  
S. Plittersdorf ◽  
W. Kiefer ◽  
N. Hüsing ◽  
U. Schubert
Keyword(s):  
Spectroscopic Analysis ◽  
Sol Gel ◽  
Raman Spectroscopic ◽  
Gel Processing ◽  
Raman Spectroscopic Analysis

Fabrication of Refractive Index Controllable Inorganic-Organic Hybrid Thick Film

2005 ◽  
Vol 287 ◽  
pp. 69-74 ◽  
Author(s):  
Sun Ho Jeong ◽  
Joo Ho Moon
Keyword(s):  
Heat Treatment ◽  
Refractive Index ◽  
Hybrid Material ◽  
Structural Changes ◽  
Sol Gel ◽  
Heat Treatment Condition ◽  
Single Spin ◽  
Organic Hybrid ◽  
Infrared Spectrometer ◽  
Lower Temperature

Inorganic-organic hybrid material was synthesized by the sol-gel process. The control of the refractive index was achieved by varying the amount of phenyltrimethoxysilane as a refractive index modifier. Thick layers of hybrid material with 22㎛ thickness were fabricated by a single spin-coating without producing any crack at lower temperature. However, the heat-treatment of the hybrid film above 200°C induced significant cracks on the surface. The refractive index variations and structural changes as a function of heat-treatment condition were analyzed using Fourier transform infrared spectrometer.

Preparation of Stoichiometric Crystalline Lithium Niobate Fibers by Sol-Gel Processing with Metal Alkoxides

1989 ◽  
Vol 72 (4) ◽  
pp. 707-709 ◽  
Author(s):  
Shin-ichi Hirano ◽  
Takashi Hayashi ◽  
Katsutoshi Nosaki ◽  
Kazumi Kato
Keyword(s):  
Lithium Niobate ◽  
Sol Gel ◽  
Metal Alkoxides ◽  
Gel Processing
Sign in / Sign up

Export Citation Format

Share Document