Precursors lead acetate

PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

Another route presented in the work cited above also finally furnished 16 and 17, although in this case, the intermediate 62, prepared in three steps from indigo (63) via the 0-acetates 64 and 65, served as the precursor leading to the key compound 61 (Scheme 10) [97H(45)1647]. Details of the synthesis of 64 had been given previously by Bergman (82CS193). 

A typical flowchart for a chelate process is shown in Fig. 2.6.46 In this process, titanium isoproproxide is first added to zirconium butoxide. Acetic acid is then added to the precursor mixture for suppression of hydrolysis. Finally, lead acetate is then added to the solution, followed by the addition of alcohol and water for control of solution viscosity, solution stability, and oligomer formation.46... 

The lead precursor in PbSe film deposition was lead acetate complexed with triethanolamine. The growth rate for PbSe was 0.18-0.16nm/cycle. The films were polycrystalline (i.e., cubic) without preferred orientation. The stoichiometry of SILAR-grown PbSe was found to be 1 1 within the limits of the RBS technique. Impurities detected were 5 at.% of oxygen and 8 at.% of hydrogen.103... 

Modification by acetylacetone is a powerful route, that allows precursor solutions to be stabilized. Interaction of titanium alkoxides with acetylacetone was extensively studied and reviewed in [1391,86]. Study ofreactions, occurring on interaction of Zr(OPrn)4 and Ti-Zr alkoxide mixture with acetylacetone, was performed in [1448] and allowed the authors to simplify the technique for preparation of precursor solution for PZT films application and to overcome the requirement of prolonged refluxing, which certainly decreases reproducibility. After dissolution of titanium and zirconium alkoxides in methoxyethanol, acetylacetone is added to form stable zirconium and titanium stock solutions. The introduction of acetylacetone allowed aqueous lead acetate (and lanthanum acetate for PLZT films) solutions to be added to mixed titanium and zirconium solutions. No reaction steps involving elevated temperatures or distillation or long reaction times are required. The solution could be used both immediately on mixing or after storage for several months. Such solutions were successfully used for application of ferroelectric films. 

Another approach to sol-gel PZT precursors involves the reaction of alkoxide mixture with glacial acetic acid [1442, 1790], Lead acetate and titanium... 

Lead sulfide is a photoconductor with an exceptionally high response in the near IR-region. It has been prepared by atomic layer epitaxy using lead halides, lead acetate or lead bis(/3-diketonate) compounds as the lead source and H2S as the sulfur source [132]. Another route to PbS is atomic layer epitaxy using Pb40(0-r-Bu)f, or polymeric [Pb(0-f-Bu)2] and H2S as precursors [133]. 

The great commercial utility of n-butane for producing acetic acid rests on the fact that as the temperature increases to 160—200° C, a high proportion of alkoxy radicals is formed both in the self-reaction of sec-Bu02 and by homolysis of initially formed sec-Bu02H these in turn lead to two-carbon fragment precursors of acetic acid, viz. 

The choices of precursor compounds for Zr, Ti, and La [40] in these examples are mainly for solubility reasons. The use of methoxyethanol as solvent has two effects first, it is a chelating agent, which prompts the dissolution of lead acetate, and second, it is an ideal solvent with enough volatility to be used in practical coating procedures. 

There is, however, one lingering concern about such products. Lead is a highly toxic metal. It poisons the enzymes that make hemoglobin. As a result, a hemoglobin precursor called aminolevulinic acid accumulates in the body and causes toxic symptoms ranging from stomach problems to brain abnormalities. The amount of lead in these dyes is very small — less than 1 percent — and studies indicate that our blood absorbs virtually none of it. But does it contaminate the hands of those who apply it And what about the excess lead acetate that winds up in our water supply ... 

Kola (Cola acuminata) extract astringent, skin treatment Zinc oxide astringent, toners Kola (Cola acuminata) extract astringent, topical Aluminum chloride hexahydrate astringent, topical hexahydrate Aluminum chloride anhydrous astringent, veterinary medicine Lead acetate trihydrate asymmetric epoxidation, transition metal catalyzed trans-Stilbene a-terpineol precursor 2-(4-Methyl-3-cyclohexenyl)-2-propanol atmosphere protectant, casting magnesium alloys... 

Self-supporting arrays composed of quadrangular nanopyramids were fabricated from water based wet chemical reaction.This water based solution method was carried out at room temperature using lead acetate and thiourea. After stirring of these two precursors in water for 20 min. 

In studies toward the synthesis of glycyrol, Kim and coworkers employed a novel precursor, iodium acetate salt 7, which was successfully incorporated into a novel Smiles rearrangement, ultimately leading to the first total synthesis of glycyrol (Figme 18.1) [4]. 

For the preparation of PZT ceramic by the sol-gel method, many precursors are available, but the typical process employs titanium isopropoxide, zirconium propoxide, and lead acetate [91]. In some syntheses, zirconium -butoxide was also used as a Zr source [90]. 

Other preparation routes of PZT powders by sol-gel synthesis used lead acetate trihydrate (Pb(OAc)2 3H2O) and zirconium acetylacetonate (Zr(AcCHAc)4) as basic precursors [92]. The solutions were dehydrated at 105 °C for 2h, and after cooling to 80 °C they were mked with the acetate solution of titanium orthotetrabutylate (Ti(OC4H9)4) in the required ratio of Pb Zr Ti = 1 0.53 0.47. A pure perovsldte phase Pb(Zro,s3Tio.47)03 was formed by calcination at 500 °C. 

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