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

Perovskite solid solutions of (La0.6Sr0.4)(X1−yMgy)O3−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 (La0.6Sr0.4)(Zr0.6Mg0.4)O3−δ and (La0.6Sr0.4)(Al0.9Mg0.1)O3−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 (La0.6Sr0.4)(Al0.9Mg0.1)O3−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.