Effect of starting particle size and vacuum processing on the yttrium barium copper oxide (YBa2Cu3Ox) phase formation

Grader, Gideon S.; Gallagher, P. K.; Fleming, Debbie

doi:10.1021/cm00006a020

Cited by 15 publications

(3 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…x 0 (12) where K is the nucleation rate coefficient and XQ is the BaCO 3 initial mass fraction. The above equation assumes a two-dimensional growth of the product following a very rapid initial nucleation (the nucleation time is negligible).…”

Section: Yba 2 Cu 3 0 7x Formation Kineticsmentioning

confidence: 99%

Influence of oxygen partial pressure on the kinetics of YBa₂Cu₃O_7−x formation

et al. 1994

View full text Add to dashboard Cite

The YBa 2 Cu3O 7 _ x formation kinetics from a spray-roasted precursor powder containing Y 2 O 3 , BaCO 3 , and CuO was followed via in situ, time-resolved x-ray diffraction as a function of gas atmosphere and temperature. In inert atmospheres, BaCO 3 and CuO form BaCu 2 O 2 which subsequently reacts with Y 2 O 3 to form YBa 2 Cu 3 06. However, YBa 2 Cu 3 06 decomposes at temperatures exceeding 725 °C with Y 2 BaCu0 5 being one of the decomposition products. In oxidizing atmospheres, YBa2Cu3O7x formation involves the BaCuO 2 . At high temperatures (800-840 °C), oxygen increases the yield of YBa 2 Cu 3 0 6 . A nuclei growth model assuming two-dimensional, diffusion-controlled growth with second-order nucleation rate fits the experimental data.

show abstract

Section: Yba 2 Cu 3 0 7x Formation Kineticsmentioning

confidence: 99%

Influence of oxygen partial pressure on the kinetics of YBa₂Cu₃O_7−x formation

et al. 1994

View full text Add to dashboard Cite

show abstract

“…Poeppel et al (1990) and Balachandran et al (1991) found that vacuum processing of a mixed oxide precursor under controlled total oxygen pressure resulted in YBa,Cu,O,+, formation at 800"C, while at atmospheric pressure, the same reaction occurred at temperatures exceeding 800°C. Grader et al (1989) found that vacuum processing of finely ground mixed-oxide precursor caused the first reaction to be almost complete at 550-60O0C, while in air the reaction occurred at temperatures higher by more than 150°C. These results indicate that CO, removal by the vacuum accelerates the reaction.…”

Section: Introductionmentioning

confidence: 99%

Effect of CO₂ concentration on YBa₂Cu₃O_6+x formation

et al. 1997

View full text Add to dashboard Cite

Two reversible reactions are involved in YBa,Cu306 + , formation: a reaction between BaCO,, and CuO forming BaCuO, and CO,, and a reaction of BaCuO, with Y,03 and CuO forming YBa,Cu306 which undergoes phase transformation to YBa,Cu306 , upon cooling. In-situ isothermal time resolved HT-XRD of a thin film was used to quantib the effect of CO, on the kinetics of the first reaction. Increased CO, partial pressure shifts the reactions to higher temperatures. At high CO, partial pressure ( >2 vol. %), the rate of the first reaction becomes essentially a step process with a very high activation eneqy. Noninstantaneous nucleation of the reaction products occurs at low CO, partialpressure (0.5-1%) and temperatures (700°C). The data fit a 2-0 difision-controlled mechanism with a zero nucleation rate for BaCO, decomposition and a second-order nucleation rate for YBa,Cu,06 formation. A comparison of the kinetics of a thin film (10 pm) as determined by HT-XRD with those of a thick sample (2 mm) determined by TG revealed that the transport of CO, within the sample pores and to the ambient gas sign$cantly affect the decomposition of BaC0,. For example, the formation of YBa,Cu306 in a thick precursor layer occurs in the 840 to 940°C range, exceeding by about 200°C that in which it is formed in thin films.formation from a spray roasted precursor

show abstract

“…Step 2 is both complicated and time consuming; thus many studies have been carried out about the mechanism [1][2][3] and technological aspects [4,5] of melt-texturing. Due to incomplete peritectic reaction some of the 211-particles are usually trapped within the 123-phase.…”

Section: Introductionmentioning

confidence: 99%