High temperature transport properties of La0.5-xPrxBa0.5CoO3-δ perovskite (x = 0, 0.2, 0.5)

Abstract

LnBaCo2O6-δ (Ln = lanthanide) are prospective materials for oxygen separation membranes. These materials show high rates of oxygen surface exchange and diffusivity, and high electrical conductivity. In this work, the La0.5-xPrxBa0.5CoO3-δ system (0 ≤ x ≤ 0.50) was studied as potential oxygen separation membrane. Samples were synthesized via a combined EDTA-citrate complexing sol-gel process at 1100 °C in air. Dense samples were obtained after 6 h calcination at 1100 °C in air. Single cubic perovskite phase (S.G.Pm3¯m) was obtained for 0 ≤ x ≤ 0.25, and tetragonal (S.G. P4/mmm) double perovskite phase for 0.30 ≤ x ≤ 0.50. Electrical conductivity (σ) was measured as a function of temperature for La0.5Ba0.5CoO3-δ (La50), La0.3Pr0.2Ba0.5CoO3-δ (La30) and Pr0.5Ba0.5CoO3-δ (La00) compounds. All the compounds have shown high electrical conductivity, reaching values between 1000 and 2000 Scm−1 at 300 °C. On increasing temperature above 300 °C, the conductivity decreases, exhibiting a metallic-like behavior, taking values of σ = 547, 385 and 714 Scm−1 at 800 °C, for La00, La30 and La50, respectively. Oxygen permeation measurements were carried out as a function of temperature between 700 and 900 °C by varying the He flux between 1 and 100 ml·min−1 on dense membranes of the same thickness (L = 1.4 mm). Ionic conductivities of 0.037, 0.054 and 0.014 Scm−1 were estimated from the oxygen permeation flux at 800 °C for La00, La30 and La50, respectively.