Фазовая диаграмма системы Cr-P

К оглавлению: Другие диаграммы (Others phase diargams)

Cr-P (Chromium-Phosphorus) M. Venkatraman and J.P. Neumann The complete Cr-P phase diagram has not been established. The solid-liquid equilibria have been determined only in the region from 0 to ~25 at.% P [39Vog] . Investigations at larger P concentrations are difficult because of the high vapor pressure of P. The following intermediate phases have been reported: Cr3P, Cr2P, Cr12P7, CrP, Cr2P3, CrP2, and CrP4. The phases generally are synthesized by direct reaction of Cr powder with red P in sealed silica tubes at elevated temperatures. The assessed phase diagram is similar to that of [Hansen]. According to [39Vog] , the diagram is similar to the Fe-P phase diagram, as indicated by the continuous solid solutions between Cr3P-Fe3P and Cr2P-Fe2P, respectively. The mutual solubilities of Cr and P, as well as the homogeneity ranges of the intermediate phases, are probably very small. The sublimation point of red P ( P = 1 bar), given as ~431 C in the assessed diagram, is taken from [Hultgren, E]. The existence of Cr3P, which has a tetragonal crystal structure, is firmly established. According to [39Vog], Cr3P melts peritectically at ~1510 C. Cr2P occurs in two crystallographic modifications, a high-temperature hexagonal form [39Vog] and a low-temperature orthorhombic form [72Roy]. The transformation temperature between these two modifications is not known. [ 39Vog] deduced the existence of Cr2P, based on investigation of the ternary system Cr-Fe-P. Although [39Vog] could not obtain the pure binary phase Cr2P, their studies indicated that it is isomorphous with Fe2P and that it melts congruently at ~1640 C. According to a crude estimate by [62Rip], CrP decomposes at ~1360 C. The higher thermal stability of CrP compared to CrN is probably due to the partially ionic bond character of CrP [54Sch]. The existence of Cr2P3, which was reported in only one investigation [14Die], is questionable. The alloy was thermally stable in a stream of hydrogen at 280 C, but transformed to CrP on heating to 440 C. In contrast to these studies, the vapor pressure measurements by [41Fal] in the region between CrP and CrP2 show no evidence for the presence of this phase. CrP2 melts between 850 and 1000 C [41Fal], its color is black [41Fal, 73Jei], it exhibits metallic conductivity [73Jei], and it has a monoclinic crystal structure [73Jei]. [41Fal] and [54Sch] prepared the CrP2 phase by reacting Cr powder and red P in sealed silica tubes at 600 to 700 C at ambient pressure; [ 73Jei] prepared the phase in boron nitride crucibles between 1000 to 1200 C at a pressure of 65 kbar. Attempts by [73Jei] to obtain CrP2 at lower pressures (45 kbar and ambient) did not succeed. Further studies are needed to clearly establish the stability of CrP2 as a function of pressure and temperature. CrP4 was prepared by reacting Cr powder and red P in boron nitride crucibles between 900 and 1200 C at pressures of 15 to 65 kbar [72Jei]. However, CrP4 is also stable at lower pressures (3 kbar) at 1000 C [72Jei]. Similar to CrP2, it is of black color and exhibits metallic conductivity [72Jei]. 14Die: Th. Dieckmann and O. Hanf, Z. Anorg. Allg. Chem., 86, 291-295 (1914) in German. 37Ars: O. Arstad and H. Nowotny, Z. Phys. Chem., 38(5), 356-358 (1937) in German. 38Now: H. Nowotny and E. Henglein, Z. Anorg. Allg. Chem., 239, 14-16 (1938) in German. 39Vog: R. Vogel and G.W. Kasten, Arch. EisenhЃttenwes., 12, 387-391 (1939) in German. 41Fal: F.E. Faller and W. Biltz, Z. Anorg. Allg. Chem., 248, 209-228 (1941) in German. 54Sch: N. Sch”nberg, Acta Chem. Scand., 8(2), 226-239 (1954). 62Lun: T. Lundstr”m, Acta Chem. Scand., 16(1), 149-154 (1962). 62Rip: R.L. Ripley, J. Less-Common Met., 4, 496-503 (1962). 62Run1: S. Rundquist, Acta Chem. Scand., 16(1), 1-19 (1962). 62Run2: S. Rundquist, Acta Chem. Scand., 16(2), 287-292 (1962). 65Aro: B. Aronsson, T. Lundstr”m, and S. Rundquist, Borides, Silicides and Phosphides, Methuen, London (1965). 65Bol: H. Boller and H. Nowotny, Monatsh. Chem., 96, 852-862 (1965) in German. 71Bau: H.E. Baurecht, H. Boller, and H. Nowotny, Monatsh. Chem., 102, 373-384 ( 1971) in German. 72Jei: W. Jeitschko and P.C. Donahue, Acta Crystallogr. B, 28, 1893-1898 (1972) . 72Owu: M. Owusu, H. Javad, T. Lundstr”m, and S. Rundquist, Phys. Scr., 6(1), 67-70 (1972). 72Roy: J. Roy-Montreuil, B. Deyris, A. Michel, A. Rouault, P. l'Heritier, A. Nylund, J.P. Senateur, and R. Fruchart, Mater. Res. Bull., 7(8), 813-826 (1972) in French. 72Sel: K. Selte, A. Kjekshus, and A.F. Andresen, Acta Chem. Scand., 26(10), 4188-4190 (1972). 73Jei: W. Jeitschko and P.C. Donahue, Acta Crystallogr. B, 29, 783-789 (1973). 73Sel: K. Selte and A. Kjekshus, Acta Chem. Scand., 27(9), 3195-3206 (1973). 79Chu: H.K. Chun and G.B. Carpenter, Acta Crystallogr. B, 35, 30-33 (1979). Submitted to the APD Program. Complete evaluation contains 1 figure, 2 tables, and 30 references. 1