Synthesis and electrical conductivity of La–Sr–X–Mg–O (X = Ti, Zr, Al) perovskite solid solution

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Perovskite solid solutions of (La 0.6Sr 0.4)(X 1− y Mg y )O 3− δ (X = Ti, Zr, Al) were prepared by a coprecipitation method using corresponding aqueous solutions and ammonium carbonate solution. The freeze-dried powders were sintered in air at 1000–1500 °C for 1–36 h. Single phase solid solutions were produced in the compositions of (La 0.6Sr 0.4)(Zr 0.6Mg 0.4)O 3− δ and (La 0.6Sr 0.4)(Al 0.9Mg 0.1)O 3− δ where (3 − δ) < 3. For the compositions of X = Ti and Zr for y = 0.1 where (3 − δ) > 3, two phases including perovskite solid solution were produced at 1400–1500 °C. The stability of perovskite solid solution was closely related to the fraction of lattice oxygen atom (3 − δ). A relatively high conductivity was measured for (La 0.6Sr 0.4)(Al 0.9Mg 0.1)O 3− δ ( σ = 4.15 × 10 −4 S/cm at 600 °C, activation energy 113.4 kJ/mol). The influence of fraction of oxide ion vacancy on the activation energy was small for δ = 0.1–0.3 of perovskite solid solution.