Abstract
The thermal expansion mechanisms of doped LaMO3 perovskites (M=Cr, Mn, Ga) in air and in the H2 atmosphere have been investigated. The dominant factors for thermal expansion behaviors of these perovskites should be the ionic bond strength between the A-site ion and oxygen ion, the change of average ionic radius of the B-site ions and the formation of vacancies in the perovskites during the thermal expansion measurement. The ionic bond strength increases by substituting a lower-valence ion at the A-site. The average ionic radius of the B-site and the formation of oxygen vacancies increase by the change of spin condition, the disproportional reaction and the reduction for the B-site ions. These increases give larger thermal expansion coefficients of the perovskites.
