Chemical Processing of Lead Metatitanate by Co-precipitation and Sol-gel Methods: The Role of Powder and Gel Characteristics on Crystallization Behavior PDF Download
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Author: Robert William Schwartz Publisher: ISBN: Category : Languages : en Pages :
Book Description
This thesis reports on preparation of PbTiO$sb3$ by two chemical methods: (i) aqueous co-precipitation and (ii) organo-metallic sol-gel processing. The effects of chemical processing conditions on material properties were determined. Particular attention was paid to the evolution of structure on heat treatment, and crystallization. Materials prepared by the two methods were amorphous in the as-prepared state, but transformed to the stable perovskite structure on heat treatment. Crystallization kinetics for the chemically prepared materials were compared with another type of amorphous PbTiO$sb3$ prepared by rapid solidification. This comparison led to the identification of material parameters which aided in crystallization. Co-precipitation was carried out by spray-atomizing a solution containing inorganic salts of lead and titanium into a continuous flow constant volume reactor. Temperature, pH, and other reactor parameters were controlled. The precipitated powders, which were dried by spray-drying, had a uniform spherical morphology with particle sizes in the micron range, and surface areas $>$100 m$sp2$/g. Crystallization into the perovskite structure occurred at 375$spcirc$C. The second chemical method was sol-gel processing of PbTiO$sb3$ from metal alkoxide solutions. Effects of hydrolysis, additive (i.e., acid or base), and drying conditions on the physical, structural, and chemical nature of the material were characterized, as was the evolution of material properties with thermal processing. Results indicated that manipulation of preparation conditions gave a significant degree of control over material properties. Correlations of material properties with preparation conditions were explained by a model which related differences in gel network structure (and structural rearrangements on heat treatment) with the level of polymeric crosslinking. Differences induced in wet gels through control of preparation conditions persisted in the amorphous and crystalline states. TEM observations indicated that densification and crystallization occurred at relatively low temperatures (400-450$spcirc$C). Lead titanate was also prepared by a third physical method, rapid solidification. Compared with the rapidly solidified material, the co-precipitated and sol-gel derived materials exhibited enhanced crystallization kinetics and lower crystallization temperatures. The chemically prepared materials were also characterized by greater surface areas and free volumes than the rapidly solidified material. The enhanced crystallization behavior was therefore believed to be at least partially due to the internal surfaces present in the chemically prepared materials.
Author: Robert William Schwartz Publisher: ISBN: Category : Languages : en Pages :
Book Description
This thesis reports on preparation of PbTiO$sb3$ by two chemical methods: (i) aqueous co-precipitation and (ii) organo-metallic sol-gel processing. The effects of chemical processing conditions on material properties were determined. Particular attention was paid to the evolution of structure on heat treatment, and crystallization. Materials prepared by the two methods were amorphous in the as-prepared state, but transformed to the stable perovskite structure on heat treatment. Crystallization kinetics for the chemically prepared materials were compared with another type of amorphous PbTiO$sb3$ prepared by rapid solidification. This comparison led to the identification of material parameters which aided in crystallization. Co-precipitation was carried out by spray-atomizing a solution containing inorganic salts of lead and titanium into a continuous flow constant volume reactor. Temperature, pH, and other reactor parameters were controlled. The precipitated powders, which were dried by spray-drying, had a uniform spherical morphology with particle sizes in the micron range, and surface areas $>$100 m$sp2$/g. Crystallization into the perovskite structure occurred at 375$spcirc$C. The second chemical method was sol-gel processing of PbTiO$sb3$ from metal alkoxide solutions. Effects of hydrolysis, additive (i.e., acid or base), and drying conditions on the physical, structural, and chemical nature of the material were characterized, as was the evolution of material properties with thermal processing. Results indicated that manipulation of preparation conditions gave a significant degree of control over material properties. Correlations of material properties with preparation conditions were explained by a model which related differences in gel network structure (and structural rearrangements on heat treatment) with the level of polymeric crosslinking. Differences induced in wet gels through control of preparation conditions persisted in the amorphous and crystalline states. TEM observations indicated that densification and crystallization occurred at relatively low temperatures (400-450$spcirc$C). Lead titanate was also prepared by a third physical method, rapid solidification. Compared with the rapidly solidified material, the co-precipitated and sol-gel derived materials exhibited enhanced crystallization kinetics and lower crystallization temperatures. The chemically prepared materials were also characterized by greater surface areas and free volumes than the rapidly solidified material. The enhanced crystallization behavior was therefore believed to be at least partially due to the internal surfaces present in the chemically prepared materials.
Author: Charles David Edward Lakeman Publisher: ISBN: Category : Languages : en Pages :
Book Description
Research is reported for the relationships that exist between processing, composition and structure development, and properties, for sol-gel derived $rm Pb(Zrsb{0.53}Tisb{0.47})Osb3$ (PZT) thin layers. Emphasis was placed on the effect of thermal processing conditions on the gel-to-ceramic conversion. In addition, the effects of interfacial reactions, and residual stresses on the measured properties were also considered. The purpose of the work was to contribute to the fundamental understanding of processes which occur during the high temperature treatment of sol-gel derived thin layers. The gel-to-ceramic conversion was monitored by transmission electron microscopy, diffuse reflectance infrared spectroscopy, and X-ray diffraction. As-deposited coatings were found to be amorphous with compositional heterogeneity at the nanoscale. This is the first report which identifies the nature of the compositional heterogeneity. Structural rearrangement occurred during thermal processing and, for slow heating (50$spcirc$C/min), the coatings approached compositional uniformity on crystallization into the perovskite phase. However, for faster heating rates, the degree of structural rearrangement was limited, thereby decreasing the shrinkage normal to the coating, and crystallization was shifted to a higher temperature. Also, for very rapid thermal processing (5000$spcirc$C/min), compositional heterogeneity was retained in the coatings after crystallization. An apparent dependence on thickness for the properties for ferroelectric PZT thin layers was observed. It was confirmed that a cover coat of a PbO-precursor deposited onto the gel-derived layers prior to firing compensated for the volatilization of PbO which occurred during heating, resulting in coatings which displayed improved properties over those prepared without a cover coat. A simple series capacitor model was investigated to interpret the data. SIMS and TEM analyses indicated that diffusion of some of the species resulted in the formation of a sub-electrode nano-crystalline phase, however, no second phases were observed between the electrode and the coating. Measurements of the residual stress state in PZT coatings deposited onto platinized silicon substrates, and fired at 700$spcirc$C, indicated a tensile stress of approximately +200MPa in the plans of the coating. Thermal expansion mismatch stresses were calculated to be of the order of $-$300MPa in compression, indicating that large tensile stresses were generated during constrained shrinkage.
Author: B. M. Melnick Publisher: ISBN: Category : Languages : en Pages : 14
Book Description
There are three stages involved in the successful application of a thin film sol-gel oxide, (1) solution synthesis, (2) application, and (3) post application treatments. Each stage contains many processing steps that can be varied in order to optimize the thin film for various applications. This work entails a statistical investigation of a thin film sol-gel PT process for use in memory applications. Statistical experimental design yields a maximum amount of information for a minimum amount of effort. Candidate controllable variables (factors) and responses are first identified. A screening experiment is then conducted to identify the most important factors based on the identified responses. A full-factorial experiment is then conducted to further evaluate the important factors. Finally, a response surface analysis is performed in order to optimize the important factors. Responses such as switching charge (2Pr), endurance and dielectric measurements are used to analyze the sol-gel lead titanate.
Author: K. Byrappa Publisher: William Andrew ISBN: 1437778364 Category : Science Languages : en Pages : 796
Book Description
Quartz, zeolites, gemstones, perovskite type oxides, ferrite, carbon allotropes, complex coordinated compounds and many more -- all products now being produced using hydrothermal technology. Handbook of Hydrothermal Technology brings together the latest techniques in this rapidly advancing field in one exceptionally useful, long-needed volume.The handbook provides a single source for understanding how aqueous solvents or mineralizers work under temperature and pressure to dissolve and recrystallize normally insoluble materials, and decompose or recycle any waste material. The result, as the authors show in the book, is technologically the most efficient method in crystal growth, materials processing, and waste treatment. The book gives scientists and technologists an overview of the entire subject including: À Evolution of the technology from geology to widespread industrial use. À Descriptions of equipment used in the process and how it works.À Problems involved with the growth of crystals, processing of technological materials, environmental and safety issues.À Analysis of the direction of today's technology. In addition, readers get a close look at the hydrothermal synthesis of zeolites, fluorides, sulfides, tungstates, and molybdates, as well as native elements and simple oxides. Delving into the commercial production of various types, the authors clarify the effects of temperature, pressure, solvents, and various other chemical components on the hydrothermal processes. - Gives an overview of the evolution of Hydrothermal Technology from geology to widespread industrial use - Describes the equipment used in the process and how it works - Discusses problems involved with the growth of crystals, processing of technological materials, and environmental and safety issues
Author: Robert William Schwartz
Author: Robert William Schwartz
Author: 
Author: Xiaoming Yang
Author: R. A. Lipeles
Author: Wei Cao
Author: Charles David Edward Lakeman
Author: Guanghua Yi
Author: Dawei Liu
Author: B. M. Melnick
Author: K. Byrappa