J. Phys. IV France 126 (2005) 7-12
The main features of GaPO hydrothermal crystal growth under conditions of direct and retrograde solubilityD.V. Balitsky1, V.S. Balitsky2, E. Philippot1, Ph. Papet1 and F. Pey1
1 LPMC UMR 5617 CNRS, University Montpellier II, France
2 IEM RAS, Chernogolovka, Russia
GaPO4 recrystallisation was studied under hydrothermal conditions at temperatures from 140 to 310C (autogeneous pressures from 2 to 150 bar). The acidic solvents of pH 4 to 0 at ambient conditions were used as mineralizers. The retrograde solubility of GaPO4 was observed under 260C (pressure up to 20 bar) and direct - above 280C (pressure above 50 bar). Low values of the initial solvent pH on GaPO4 solubility at temperatures up to 260C have an influence to increase GaPO4 solubility and in the same time decrease crystalline quality, for example, rise of OH content is observed. Some solvents with pH near to 4 tested as mineralizers exhibit low solubility of GaPO4, but increasing value at temperatures above 280C and lead to an attractive crystal growth. So, a possible explication of this phenomenon is a formation of few stable phases from an initial solution which can participate or no in reactions with GaPO4 at certain T-P conditions.
© EDP Sciences 2005