The preparation and properties of La3.5Ru4O13 and La2RuO5

The stability of the La3.5Ru4O13 and La2RuO5 compounds in the La-Ru-O system in various atmospheres and various temperature ranges was investigated by thermal analysis, X-ray diffraction analysis and electron microscopy. The La3.5Ru4O13 compound is stable in oxidizing and neutral atmospheres (N2 with 10 ppm O2), while La2RuO5 is partially reduced in a neutral atmosphere to form La2RuO4.6. In a reducing atmosphere both compounds decompose into metallic Ru and La2O3. The thermal expansion coefficients of La2RuO5 and La3.5Ru4O13 at 800 °C are 11.2 × 10−6 K−1 and 9.3 × 10−6 K−1, respectively. The specific electrical resistivity for La3.5Ru4O13 is relatively independent of temperature and is 2 × 10−2 Ω cm at 800 °C, while for La2RuO5 it decreases with increasing temperature and is 1 Ω cm at 800 °C.