Effects of PtO2 and CeO2 additives on the microstructures of the quenched melts of Y-Ba-Cu-O materials

Riches, J. D., Alarco, J. A. and Barry, J. C. (2000) Effects of PtO2 and CeO2 additives on the microstructures of the quenched melts of Y-Ba-Cu-O materials. Physica C: Superconductivity, 336 1-2: 43-56.


Author Riches, J. D.
Alarco, J. A.
Barry, J. C.
Title Effects of PtO2 and CeO2 additives on the microstructures of the quenched melts of Y-Ba-Cu-O materials
Formatted title Effects of PtO2 and CeO2 additives on the microstructures of the quenched melts of Y–Ba–Cu–O materials
Journal name Physica C: Superconductivity
Publication date 2000-07
Sub-type Article
DOI 10.1016/S0921-4534(00)00025-3
Volume number 336
Issue number 1-2
ISSN 0921-4534; 1873-2143
Start page 43
End page 56
Total pages 14
Place of publication Amsterdam, Netherlands
Publisher Elsevier Science BV
Collection year 2000
Language eng
Subject C1
240203 Condensed Matter Physics - Electronic and Magnetic Properties; Superconductivity
780102 Physical sciences
Formatted abstract The microstructures of the quenched melts of samples of Y123 and Y123+15–20 mol% Y211 with PtO2 and CeO2 additives have been examined with optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDS) and X-ray Diffractometry (XRD). Significantly higher temperatures are required for the formation of dendritic or lamellar eutectic patterns throughout the samples with PtO2 and CeO2 additives as compared to samples without additives. The BaCuO2 (BC1) phase appears first in solid form and, instead of rapidly melting, is slowly dissolving or decomposing in the oxygen depleted melt. PtO2 and CeO2 additives slow down or shift to higher temperatures the dissolution or decomposition process of BC1. A larger fraction of BC1 in solid form explains why samples with additives have higher viscosities and hence lower diffusivities than samples without additives. There is also a reduction in the Y solubility to about half the value in samples without additives. The mechanism that limits the Ostwald ripening of the Y211 particles is correlated to the morphology of the quenched partial melt. It is diffusion controlled for a finely mixed morphology and interface-controlled when the melt quenches into dendritic or lamellar eutectic patterns. The change in the morphology of the Y211 particles from blocky to acicular is related to an equivalent undercooling of the Y–Ba–Cu–O partial melt, particularly through the crystallization of BC1.
© 2000 Elsevier Science B.V. All rights reserved.
Keyword Y–Ba–Cu–O
Liquid phase
PtO2 additives
CeO2 additives
Melt processing
Q-Index Code C1

Document type: Journal Article
Sub-type: Article
Collections: School of Physical Sciences Publications
Centre for Advanced Imaging Publications
 
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