Subsolidus equilibria in air in the La2O3–Ga2O3–NiO system were studied with the aim of obtaining information on possible interactions between a LaGaO3-based solid electrolyte and NiO during preparation of the anode in solid oxide fuel cells (SOFC). No ternary compound was found. The tie lines are between La4Ga2O7 and La2NiO4, LaGaO3 and La2NiO4, LaGaO3 and NiO, and LaGaO3 and NiGa2O4.

Subsolidus phase relations in the BaTiO3–La2TiO5–TiO2 part of the ternary BaO–La2O3–TiO2 system at 1300 °C in air were determined. The phases were characterized by x-ray diffraction, scanning electron microscopy, and electron probe wavelength dispersive spectroscopic microanalysis. A combination of techniques was employed because of insensitivity in detecting secondary phases by x-ray diffraction. The location and extent of Ba6−xLa8+2x/3Ti18O54 ternary solid solution 0.2(1) ⩽ x ⩽ 2.3(1) and Ba1−yLayTi1−y/4 (VTi)y/4O3 binary solid solution 0 ⩽ y ⩽ 0.3 at 1300 °C was established. Tie lines between various barium polytitanates with a sequence of Ba6−xLa8+2x/3Ti18O54 solid solution regions were determined.

RuO2 single crystals were obtained by evaporation of PbO from Pb2Ru2O6.5 at high temperatures and were verified as good standards for WDS analysis. They were used for the investigation of phase equilibria and the extent of solid solubility in the RuO2–TiO2 system by WDS quantitative microanalysis. The solid solubility at 1350 °C was determined to be 16.5% TiO2 in RuO2 and 13.5% RuO2 in TiO2.