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The reaction pathway for the formation of Tl-2223

机译：Tl-2223形成的反应途径

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The reaction pathway for the formation of Tl2Ba2Ca2Cu3Oz (Tl-2223), a promising compound for applications in passive microwave devices, has been investigated by in situ neutron powder diffraction. The experiments were carried out in an initially evacuated closed system on two samples with compositions Tl1,7Ba2Ca2Cu3O2 and Tl2,3Ba2Ca2Cu3Oz. We find that, under the conditions specified above, the formation path implies Tl2BaO4, Tl6Ba4O13 and Tl-2212 according to the sequence: precursors/oxides --> Tl2BaO4 --> Tl6Ba4O11 --> Tl-2212 --> Tl-2223. The difference with respect to the sequence observed when the experiments are carried out in an open atmosphere (precursors/oxides --> Tl-2201 --> Tl-2212 --> Tl-2223) is explained by the low temperature reaction between the TlOx vapour which becomes appreciable at 700 K in closed system and the free BaO resulting from the decomposition of BaCuO2, The conversion from Tl-2212 to Tl-2223 occurs at 800 degreesC and does not involve the formation of a liquid phase but the solid state diffusion of the Ca and Cu species and the restructuring of the Tl-2212 lattice. This conversion however does not occur when the Tl content is equal to 2.3 in agreement with previous reports on phase equilibria. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 9]
机译：通过原位中子粉末衍射已经研究了形成Tl2Ba2Ca2Cu3Oz（Tl-2223）的反应途径，这是一种用于无源微波设备的有前途的化合物。实验是在最初抽成真空的封闭系统中对组成为Tl1,7Ba2Ca2Cu3O2和Tl2,3Ba2Ca2Cu3Oz的两个样品进行的。我们发现，在上述条件下，形成路径根据以下顺序暗示了Tl2BaO4，Tl6Ba4O13和Tl-2212：前体/氧化物-> Tl2BaO4-> Tl6Ba4O11-> Tl-2212-> Tl-2223。在露天环境下进行实验时观察到的序列差异（前体/氧化物-> Tl-2201-> Tl-2212-> Tl-2223）是由于两者之间的低温反应所致。 TlOx蒸汽在700 K的密闭系统中变得可观，而游离BaO是由BaCuO2分解产生的。Tl-2212到Tl-2223的转化发生在800摄氏度，并且不涉及液相的形成，而是固态的Ca和Cu物种的扩散以及Tl-2212晶格的重组。然而，当T1含量等于2.3与先前关于相平衡的报告一致时，不会发生这种转化。 （C）2002 Elsevier Science B.V.保留所有权利。 [参考：9]

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