Crystallization in Systems PbO-TiO2-KF-H2O and PbO-ZrO2-KF-H2O

Abstract

In a previous communication [1] we considered the crystallization of titanium, zirconium, and hafnium oxides under hydrothermal conditions. In the present case we shall consider the crystallization of more complicated compounds containing titanium and zirconium. The principal subjects for consideration will be the systems PbO-TiO2 -KF-H2O and PbO-ZrO2-KF-H2O, these being studied in order to determine the conditions governing the synthesis and recrystallization of lead metatitanate and metazirconate (PbTiO3, PbZrO3). The choice of KF solutions as media for the synthesis and recrystallization of PbTiO3 and PbZrO3 was based on the results of our previous communication [1], in which* we demonstrated the possibility of transporting titanium and zirconium by these solutions. However, we also studied a number of other solvents of the kind most frequently used in hydrothermal investigations for the case of the PbO-TiO2-X-H2O system (X = solvent): alkalis, chlorides, sulfates, borates, and so on. We found that in the quaternary PbO-TiO2-X-H2O system titanium behaved very much the same as in the TiO2-X-H2O ternary system (formation of alkali titanates in solutions of sodium and potassium carbonates and hydroxides, low mobility in sulfate and borate solutions, etc.), thus constituting the most inert component of the system. Only in KF solutions was the recrystallization of PbTiO3 achieved. Analogous results were obtained in the PbO-ZrO2-X-H2O system, in which KF was also the most “suitable” solvent for the synthesis and recrystallization of lead zirconate.*