The system ZnO-Ti02 has been investigated using quenching, hydrothermal, strip-furnace, and solid-state-reaction techniques. Two compounds were found: Zn2Ti04, which melts congruently at 1549"C., and ZnTiOs, which dissociates hydrothermally at 945°C. to give Zn2Ti04 and rutile. Two eutectics were found: one between ZnO and Zn2Ti04 at 32 mole % TiO, and 1537°C. and the other between ZnzTiOl and TiO? at 58 mole yo Ti02 and 1418°C. Rutile was the only modification of TiO, observed. The reported melting points of ZnO and TiO, are 1975" and 1830°C. respectively; however, data exist which indicate the sublimation of ZnO at atmospheric pressure. Loss of ZnO by volatilization slightly decreased the accuracy of the liquidus relations. Reported solid solutions of TiO, in Zn2Ti04 and ZnTiOs were not encountered, and explanations of this discrepancy are proposed.

The system BaO-Ti02 was investigated using quenching, strip-furnace, and thermal techniques. Five compounds were found to exist in the system: BazTi04, BaTiOa, BaTizOa, BaTi307, and BaTi409. Of these, only barium metatitanate (BaTi03) melts congruently (at 1618°C.). The dititanate melts incongruently at 1322°C. to yield BaTiOr and liquid ; the trititanate melts at 1357OC. to yield BaTi409 and liquid; the tetratitanate melts to TiOz and liquid at 1428OC. The nature of melting of the orthotitanate could not be determined accurately because of the high temperature involved and the rapid reaction with platinum. The two eutectics in the system occur between BazTi04 and BaTiOs at 1563°C. and between BaTizOs and BaTi307 at 1317OC. The temperature of the cubic-hexagonal transition in barium metatitanate was determined as 146OOC. and the transition has been shown to be reversible. The transition temperature is raised sharply by the addition of a small percentage of TiOz although the extent of solid solution is quite limited. Some applications to the manufacture of titanate bodies and to the growth of single crystals of barium metatitanate are discussed.

The system BaTiOrSiOz is characterized by two congruently melting compounds and a compound having a subsolidus stability maximum. A barium analogue of the mineral sphene, BaTiSiOa, was shown to melt congruently at 1400OC. and BaTiSizO7 melted congruently at 125OOC. The gem mineral benitoite (BaTiSi30s) was synthesized hydrothermally and was shown to decompose below the solidus to form BaTiSi207 and SiOz when heated above 965OC. hydrothermally or above 105OOC. dry. Three eutectics in the system were determined: at 1245OC. and 70 mole % SiO,, at 1246OC. and 63% SiO2, and at 1260OC. and about 29% Si02. Glasses with high refractive indices were obtained over a limited range of compositions. The cubichexagonal transition temperature in barium titanate was raised sharply by small additions of silica. The maximum inversion temperature observed was 1575OC. and must have been due to limited solid solution of SiOn in BaTiOa.