Synthesis and Properties of Lanthanum Sodium Manganate Perovskites Crystals

Crystals up to 4 mm on the edge of sodium-substituted lanthanum manganates with the rhombohedral perovskite structure have been grown for the first time using fused salt electrolysis at 980–1000°C. Cs2MoO4–MoO3 mixtures have been employed as solvents. Substitution of Na for La appears to be limited to about 12 at.%. All the phases prepared have an average Mn valence of 3.26(2) which is a result of decreasing A-site vacancies as the Na content is increased. The Curie and insulator–metal transition temperatures increase with increasing Na content with values of 300–320 K being observed for samples containing 10–12 at.% Na. Magnetoresistance values (5 T field) of ~62% at 300 K with a maximum value of 76% at 280 K were observed for a sample of composition Na0.099La0.889Mn0.996O3