Lanthanum chromite based perovskites for oxygen transport membrane

Judicious selection of mixed ionic–electronic conducting (MIEC) perovskite oxide as oxygen transport membrane (OTM) offers the potential to enhance overall process economics and systems performance for a wide variety of industrial applications ranging from clean and efficient energy conversion (oxy-combustion) to selective gas separation (high purity oxygen production) and value added chemicals (syngas and liquid fuel) production with near-zero greenhouse gas emissions. Doped lanthanum chromite perovskites have been considered as promising material of choice for oxygen transport membrane (OTM) due to their superior thermo-chemical stability in aggressive environment (800–1000 °C, 0.21–10−20PO2PO2) than the other mixed ionic–electronic conducting (MIEC) perovskites such as ferrites and cobaltite's. Thermo-physical properties of the lanthanum chromite, required for optimum oxygen transport can be tuned by modifying the crystal structure, chemical bonding, and ionic and electronic transport properties through selection of dopant's type and level. A perspective on the development of lanthanum chromite-based oxygen transport membranes is presented with an insight based on the pertinent literature and data analysis. The role of various A- and B-site dopants on the crystal structure, densification, thermal expansion, electrical transport, oxygen permeation, mechanical properties, and thermochemical stability of lanthanum chromite is discussed to enlighten ‘composition–structure–property’ correlations. It has been found that: the preferred dopants are strontium at A-site and manganese, nickel, iron, and titanium at B-site to obtain the desired thermo–chemo–electro–mechano properties. Challenges for long term performance and structural stability of doped lanthanum chromite as an oxygen transport membrane are outlined for the applications under ‘real system’ exposure conditions.