Phase Stability Solubility and Hydrothermal Crystal Growth of PbTiO sub 3

PbTiO sub 3 phase stability and crystal growth were investigated under hydrothermal conditions near 500C. Solubility of PbTiO sub 3 was measured from 350-600C; dependence on pressure and mineralizer was also determined. The PbO-TiO sub 2-H sub 2 O phase diagram in 3.2km KF shows a narrow region of PbO fraction 45.9-53.1% (Pb/Ti ratio 0. 87-1.13) in which PbTiO sub 3 is the only solid product a determined by powder X-ray diffraction. Regions on the PbO-rich side produce PbO plus PbTiO sub 3, and regions on the TiO sub 2-rich side yield PbTi sub 3 O sub 7 plus PbTiO sub 2. Solubility displays a positive temperature dependence with an estimated heat of solution DELTA H sub (sol) = 50 kJ/mol (12 kcal/mol). No appreciable solubility-pressure dependence is observed in the range of 10,000-30,000 psi (69-207 MPa). The solubility increases with KF concentration, then drops somewhat between 5. 6-7 8m KF. Decomposition of PbTiO sub 3 occurs when KF molalities exceed 7. 8m. Hydrothermally grown crystals are yellow in color and are tablet- shaped. X-ray diffraction and EDS of grown crystals verify identity of the crystals to be PbTiO sub 3. Crystal size increased dramatically between 485-600C, with a significant decrease in optical crystal quality as the growth temperature increases.