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Influences of the 'A' and 'B' site c...

Gersten, Bonnie Lynn.

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Influences of the 'A' and 'B' site cation species in the kinetics of hydrothermal synthesis of ABO(3) perovskite-type materials.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Influences of the 'A' and 'B' site cation species in the kinetics of hydrothermal synthesis of ABO(3) perovskite-type materials./
作者:	Gersten, Bonnie Lynn.
面頁冊數:	343 p.
附註:	Source: Dissertation Abstracts International, Volume: 61-05, Section: B, page: 2550.
Contained By:	Dissertation Abstracts International61-05B.
標題:	Chemistry, Physical. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9973314
ISBN:	0599786116

Influences of the 'A' and 'B' site cation species in the kinetics of hydrothermal synthesis of ABO(3) perovskite-type materials.
Gersten, Bonnie Lynn.

Influences of the 'A' and 'B' site cation species in the kinetics of hydrothermal synthesis of ABO(3) perovskite-type materials. - 343 p.

Source: Dissertation Abstracts International, Volume: 61-05, Section: B, page: 2550.

Thesis (Ph.D.)--Rutgers The State University of New Jersey - New Brunswick, 1999.

A study was conducted to determine the effect of the 'A' and 'B' site cations in the kinetics of the low temperature (below 200°C) hydrothermal. synthesis of the ABO3 perovskites (i.e., BaTiO3, SrTiO3, Ba0.5Sr0.5TiO 3, PbTiO3, PbZrO3 and PbZr0.52Ti 0.48O3). A thermodynamic model of aqueous solutions was applied to assure phase-pure synthesis conditions and to differentiate thermodynamics from kinetics. Optimal synthesis conditions of pH, temperature and initial reagent concentrations including EDTA complexes for the formation of phase-pure perovskites were found. The EDTA was found to decrease PbO formation in lead-based perovskites, decrease carbonate formation in alkaline-earth metal titanates, and to prevent phase separation in the Ba-Sr-Ti hydrothermal system. Theoretical predictions were experimentally validated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic absorption spectroscopy (AA). Although the model predicted the formation of phase-pure perovskites at all temperatures (25--200°C), in practice temperatures greater than 25°C were required. The minimum reaction temperature for reactions within 3 days varied from 70--140°C depending on the pH and initial reagent concentrations. Crystalline PbTiO3 could be prepared at temperatures as low as 70°C with a Pb/EDTA and Pb/Ti molar ratio of 2. However, BaTiO3 and SrTiO3 could be prepared at 80°C with or without EDTA. Ba0.5Sr0.5TiO3 could be prepared with EDTA at temperatures as low as 90°C. However, phase separation into BaTiO 3 and SrTiO3 resulted without EDTA. Below the minimum reaction temperatures, the reactions were incomplete due to sluggish reaction kinetics rather than unfavorable thermodynamics.

ISBN: 0599786116Subjects--Topical Terms:

560527
Chemistry, Physical.

Influences of the 'A' and 'B' site cation species in the kinetics of hydrothermal synthesis of ABO(3) perovskite-type materials.
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500 $a Source: Dissertation Abstracts International, Volume: 61-05, Section: B, page: 2550.
500 $a Director: Richard Edward Riman.
502 $a Thesis (Ph.D.)--Rutgers The State University of New Jersey - New Brunswick, 1999.
520 $a A study was conducted to determine the effect of the 'A' and 'B' site cations in the kinetics of the low temperature (below 200°C) hydrothermal. synthesis of the ABO3 perovskites (i.e., BaTiO3, SrTiO3, Ba0.5Sr0.5TiO 3, PbTiO3, PbZrO3 and PbZr0.52Ti 0.48O3). A thermodynamic model of aqueous solutions was applied to assure phase-pure synthesis conditions and to differentiate thermodynamics from kinetics. Optimal synthesis conditions of pH, temperature and initial reagent concentrations including EDTA complexes for the formation of phase-pure perovskites were found. The EDTA was found to decrease PbO formation in lead-based perovskites, decrease carbonate formation in alkaline-earth metal titanates, and to prevent phase separation in the Ba-Sr-Ti hydrothermal system. Theoretical predictions were experimentally validated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic absorption spectroscopy (AA). Although the model predicted the formation of phase-pure perovskites at all temperatures (25--200°C), in practice temperatures greater than 25°C were required. The minimum reaction temperature for reactions within 3 days varied from 70--140°C depending on the pH and initial reagent concentrations. Crystalline PbTiO3 could be prepared at temperatures as low as 70°C with a Pb/EDTA and Pb/Ti molar ratio of 2. However, BaTiO3 and SrTiO3 could be prepared at 80°C with or without EDTA. Ba0.5Sr0.5TiO3 could be prepared with EDTA at temperatures as low as 90°C. However, phase separation into BaTiO 3 and SrTiO3 resulted without EDTA. Below the minimum reaction temperatures, the reactions were incomplete due to sluggish reaction kinetics rather than unfavorable thermodynamics.
520 $a The phase-pure synthesis conditions were used in the preparation of the perovskites for reaction rate studies. Samples were extracted from a reflux condenser as a function of time and were characterized. Comparisons of the induction time, reaction time, and apparent activation energies were made. For example, in the formation of PbTiO3, the reaction time and induction time was found to decrease with a decrease in titania precursor size, an increase in temperature, KOH concentration, Pb/EDTA and Pb/Ti molar ratios, and precursor concentration. The apparent activation energy was found to decrease with an increase in KOH concentration from 101 kJ/mol with 2.5 m KOH to 47 kJ/mol with 7.8 m KOH. Under similar conditions, the apparent activation energies for BaTiO3, SrTiO3, and PbTiO 3 were 107, 91 and 47 kJ/mol, respectively. PbTiO3 formation required longer reaction times and induction times than BaTiO3 and SrTiO3. Nielsen's growth equations were applied to experimental data and provided support for surface controlled growth by a dissolution-precipitation mechanism.
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