Optical and electromagnetic properties of LaCo[O.sub.3]:[Li.sup.+];[M.sup.2+]

Lanthanum cobaltates modified by alkaline-earth-metal (0.10 mol%) and lithium (0.05 mol%) ions were synthesized. The samples had an orthorhombic distorted perovskite-like structure according to x-ray diffraction phase analysis. Addition of [Li.sup.+] and [M.sup.2+] (M = Ca, Sr, Ba) to the LaCo[O.sub.3] matrix was shown to increase the unit-cell parameters, the optical band width (Eg), and the average Co oxidation state ([Co.sup.n+]). Pure and doped LaCo[O.sub.3] were characterized by the presence of paramagnetic centers as isolated structural and surface [Co.sup.2+] ions and adsorption complexes [[Co.sup.3+] ... [O.sup.-.sub.2]] * on the surface of the oxide matrix at a concentration that increased in the order Ba > Sr > Ca. The cobaltates were found to possess Mott hopping conduction in the temperature range 77-298 K.