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YILUK(bible2代发): 金币+5, OK 2016-06-24 19:38:27
Al2O3-SiO2-P2O5
Fig. 93-156—System P2O5-SiO2-Al2O3. Solid state phase relationships in air from 900¡ã-1100¡ãC. Mul = Al6Si2O13; Trd = tridymite (SiO2).
R. Umlauf, H. Von Platen, A. A. Forughi, and P. Bartha, Ber. Dtsch. Keram. Ges., 57 [4-5] 83-85 (1980).
An unspecified number of compositions were prepared, using unspecified raw materials. Samples were annealed at 300¡ã, 600¡ã, 700¡ã, 900¡ã, and 1100¡ãC for periods up to 25 d. Loss of P2O5 was avoided through the use of double-crimped Au-Pt tubes to contain all mixtures. Phase identification was performed using Guinier X-ray diffraction, with CuKa radiation and Si as internal standard.
The ternary compound was found to be formed reproducibly at all temperatures above 700¡ãC, with some indication of phase formation below that temperature. The chemical formula Si2AlP3O13 was determined using an energy-dispersive microprobe system (average of 45 measurements on 4 specimens). The compound exists in two stable crystallographic modifications; a third modification is obtained irreproducibly on grinding the crystal. Both stable modifications exhibit hexagonal prismatic growth habit and have negative optical extinction. Indexed X-ray data for the stable modifications are given, determined from single-crystal precession X-ray diffraction (MoKa radiation) from selected fragments of both crystal types. The high-temperature phase is said to be trigonal, space group P321, P3m1, or P3¡￥m1, with a = 3.212 nm and c = 0.886 nm, but powder data can be indexed using a hexagonal pseudocell with a = 0.803 nm and c = 0.886 nm. The stable, low-temperature phase is hexagonal, space group P6322, with a = 0.801 nm and c = 0.920 nm.
Figure 364 shows a compound, Si2P2O9, but Ref. 1 confirms the composition as Si5P6O25.
The principal ternary phase assemblages indicated are as determined by Forughi.2 Tie-lines in two-phase regions have been added for clarity by the editors.
1. A. E. Mal'shikov, Zh. Neorg. Khim., 32 [10] 2370-2374 (1987); Russ. J. Inorg. Chem. (Engl. Transl.), 32 [10] 1383-1385 (1987).
2. A. A. Forughi; "Phase Relations in Al2O3-P2O5 and SiO2-Al2O3-P2O5 Systems"; Ph.D. Dissertation. Johannes-Gutenberg-University Mainz, Mainz, Germany, 1974.
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