Effects of cation substitution on thermal expansion and electrical properties of lanthanum chromites

摘要

The effects of cation substitution on the sintering characteristics, thermal expansion and electrical conductivity properties of La(AE)Cr(M)O_3 (AE=Mg, Ca, Sr, M=Ni, Cu, Co) were investigated. The sinterability of alkaline metal earth (AE)-doped LaCrO_3 increased with AE contents in a sequence of Ca > Sr > Mg. Sr-doped LaCrO_3 sample had a TEC compatible with that of 8YSZ electrolyte. The transition metals of Ni, Co and Cu substituted in Cr-site further optimized the sinterability of La_(0.85)Sr_(0.15)CrO_3 in air. Ni and Co could effectively enhance the electrical conductivity from room temperature to 1123 K though the concomitant increase in TEC was distinctively large with Co doping. The TEC was controlled by co-doping Ni and Co in Cr-site, and La_(0.85)Sr_(0.15)Cr_(0.95)Ni_(0.02)Co_(0.02)O_3 exhibited a TEC of 10.9 X 10~(-6)/K, which was matched with that of 8YSZ, indicating that it could be suitable to be used as an SOFC interconnect material.