An exploratory study on solution assisted synthetic routes to prepare nano-crystalline La 1− xM xGa 1− yN yO 3± δ (M = Sr, □; N = Mn, Mg) for IT-SOFC applications

Abstract

Nano-crystalline La 1− x M x Ga 1− y N y O 3± δ (M = Sr; □ (vacancy), x = −0.10 to 0.15; N = Mn, Mg; y = −0.10 to 0.15) compositions were synthesized by various wet chemical methods. The La- or Ga-deficient compositions are attempted to avoid substitution of aliovalent cations which can facilitate the formation of single phase at relatively low temperature by restoring the nano-crystalline nature of the powders. The wet chemical methods like metal–carboxylate gel decomposition, hydroxide co-precipitation and regenerative sol–gel process followed by microwave sintering in a very short interval time (30 min) of the powders were attempted at ∼1200 °C. The powders were characterized by various techniques like XRD, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The grain size measured was ∼22 nm range. The electrical conductivities of the compositions were measured by ac and dc techniques. The conductivity of a sintered pellet was found to be ∼0.01–0.21 S cm −1 at 550–1000 °C range, respectively. The influence of process parameters on the properties of the materials based on experimental observations and literature data is discussed. The advantages of nano-crystalline nature of the powders over microcrystalline powders synthesized by the conventional methods of preparation were brought out. The effect of wet chemical methods especially regenerative sol–gel in producing nano-crystalline perovskites with multi-element substitutions at A- and B-sites (of ABO 3) to achieve physico-chemical compatibility for fabricating zero emission all perovskite IT-SOFCs has been reported.