Wong-Ng Winnie, Cook Lawrence P
National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
J Res Natl Inst Stand Technol. 1998 Jul-Aug;103(4):379-403. doi: 10.6028/jres.103.023. Epub 1998 Aug 1.
This paper describes the melting equilibria in the vicinity of the high phase BaYCuO , including evidence for two Ba-Y-Cu-O immiscible liquids. Melting equilibria have been investigated in purified air using a combination of differential thermal analysis (DTA), thermogravimetric analysis (TGA), powder x-ray diffraction (XRD), MgO wick entrapment of liquid for analysis, scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDS), and hydrogen reduction for determination of copper oxidation state. For relatively barium-rich compositions, it was necessary to prepare the starting materials under controlled atmosphere conditions using BaO. A liquidus diagram was derived from quantitative data for the melts involved in various melting reactions. In general the 1/2(YO) contents of the melts participating in these equilibria were low (mole fraction <4 %). The primary phase field of BaYCuO occurs at a mole fraction of <2.0 % 1/2YO and lies very close along the BaO-CuO edge, extending from a mole fraction of ≈43 % CuO to a mole fraction of ≈76 % CuO. It is divided by a liquid miscibility gap and extends on either side about this gap. The topological sequence of melting reactions associated with the liquidus is presented as a function of temperature. Implications for the growth of BaYCuO crystals are discussed.
本文描述了高温相BaYCuO附近的熔化平衡，包括两种Ba - Y - Cu - O不混溶液体的证据。利用差示热分析（DTA）、热重分析（TGA）、粉末X射线衍射（XRD）、用MgO芯吸捕集液体进行分析、扫描电子显微镜（SEM）结合能量色散X射线分析（EDS）以及用氢还原法测定铜的氧化态等方法，在净化空气中研究了熔化平衡。对于相对富钡的成分，有必要在使用BaO的受控气氛条件下制备起始材料。根据各种熔化反应中熔体的定量数据得出了液相线图。一般来说，参与这些平衡的熔体中1/2(YO)的含量较低（摩尔分数<4%）。BaYCuO的初相区出现在1/2YO摩尔分数<2.0%处，并且沿着BaO - CuO边非常靠近，从约43% CuO的摩尔分数延伸到约76% CuO的摩尔分数。它被一个液体互溶间隙分开，并在该间隙两侧延伸。给出了与液相线相关的熔化反应的拓扑序列随温度的变化情况。讨论了对BaYCuO晶体生长的影响。
