Study of Equilibrium Phase Diagram Around Langasite

Study of Equilibrium Phase Diagram Around Langasite [9] 

The basic process was to melt the powder completely and then cool it to observe the crystaUized phases in order to estabhsh the liquidus phase relations. The crucibles were suspended in the thermal center of a resistance furnace from which the crucibles could be dropped into water of room temperature. Samples were heated to 1580 °C and held for 3 h for complete melting and then were cooled down by different methods. The first method was continuous cooling from 1580 °C to room temperature. In this way, the whole process of crystalHzation was completed, thus the phases representing the crystallization path could be obtained. In order to confirm the crystallization sequence of the obtained phases in the continuously 

In-situ observations were performed by preparing a self-made apparatus to confirm the crystallization sequence of the phases obtained from the melt. Pt boats with a length of 15 mm and a width of 2 mm were heated by DG current passed through them. Powder of the calcined samples was charged in the center region of the Pt boats and the whole process of melting and crystalHzation was observed through a microscope set above the Pt boats. Since the temperature distribution on the Pt 

The phases presented in the calcined samples were identified by XRD using Cu as a target. The proportion of each phase was estimated by the ratio of the intensities of its diffraction peaks to that of its standard sample. Phases were also determined by scanning electron microscope (SEM) observation and simultaneous EPMA. The crystallization sequence of the phases in the continuously cooled samples was estimated by the appearance of different phases based on the fact that the first crystallized phases are usually relatively large euhedral crystals while phases crystallized thereafter are usually either eutectics or peritectics among them. The crystallization sequence was also confirmed by EPMA measurement on in-situ observed samples. 

The Ga203-poor portion of the system, where the ternary compound was observed, was of great interest because a Ga203-poor phase was frequently crystaUized in the continuously cooled samples as wiU be described in Section 15.3.6. DiHerent from the previous report where the soHd solubility of Lai4 Sig O39 was not mentioned 

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