Synthesis and electrical properties of Sr₃NiNb₂O₉ – materials for SOFCs

摘要

Perovskite-based anodes for Solid Oxide Fuel Cells (SOFCs) have received attention in recent years due to mixed ionic and electronic conductivity and good properties. This pap er presents the synthesis and electrical conductivity of Sr 3 NiNb 2 O 9 -based compounds. Sr 3 NiNb 2 O 9 -based compounds were synthesized using a conventional solid-state reaction in air. The structure of perovskite-related compounds with the co mposition of Sr 3 Ni 1+x Nb 2-x O 9 (0≤x≤1) was evaluated analyzing the evolution with composition of the X-ray diffraction patterns (PXRD). The pure SrNi 0.33 Nb 0.67 O 3 phase (JCPDS: 17-0179) was found for Sr 3 Ni 1+x Nb 2-x O 9 (0≤x≤0.25). With the increase of Ni content, the second phase NiO appeared. The Electrical conductivity of Sr 3 NiNb 2 O 9 in air, H 2 and wet H 2 atmospheres from 300 o C to 800 °C by subsequent heating and cooling cycles was determined by AC impedance using Pt electrodes. The spectra show somewhat depressed arcs. The contributions due to bulk (b), grain -boundary (gb), and electrode (e) effects were observed at high, intermediate and lo w-frequency regions, especially at low temperatures. The electrical conductivity of the Sr 3 NiNb 2 O 9 co mpounds was found to vary in different atmospheres (air, H 2 and wet H 2 ). The electrical conductivity increases in H 2 compared to air. In H 2 , the Sr 3 NiNb 2 O 9 compounds exhibit 2.22 x 10 -3 S.cm -1 at 625 o C, which is about four orders of magnitude higher than that in air. The activation energy was found to be 1.17 eV, 0.72 eV, 0.83 eV in air, dry H 2 and wet H 2 respectively.