STRUCTURE AND MICROTEXTURE CHANGES IN PHOSPHORUS-BEARING CA2SIO4 SOLID-SOLUTIONS

The crystal structure and microtexture of P-bearing Ca2SiO4 solid solutions (C2S(ss)) were studied as a function of x = P/(Si + P) ranging from 0.085 to 0.398. All the samples were prepared at the stable-temperature region of the alpha-phase and quenched in air. The structures were described in terms of the orthohexagonal or hexagonal cell of the former alpha-phase. The crystal with x = 0.085 was composed entirely of the orthorhombic alpha(L)'-phase, the modulation wavelength of which was N = 3 along the c-axis. With x = 0.118 and 0.156, the crystal grains were made up of both alpha'(L) and incommensurate orthorhombic phases. The volume fraction of the alpha(L)'-phase decreased with increasing x. With x = 0.197, the crystal was made up exclusively of the incommensurate phase, with the modulation wave vector k given by (1/N) a* + c*. A good correlation N = 4.370 - 2.50x was observed between N (3.75 less-than-or-equal-to N less-than-or-equal-to 4.09) and x (0.118 less-than-or-equal-to x less-than-or-equal-to 0.250). The crystal with x = 0.398 consisted of a single hexagonal phase. The modulation wavelength was N = 2 along the a-axis and N = 3 along the c-axis.