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.