Crystal structures and magnetic properties of alkali-metal lanthanide oxides A2LnO3 (A = Li, Na; Ln = Ce, Pr, Tb)

We have prepared alkali-metal lanthanide oxides A2LnO3 (A = Li, Na; Ln = Ce, Pr, Tb). Li2PrO3 crystallizes orthorhombically with space group Cmmm. The Pr atoms are octahedrally coordinated by six oxygen atoms and the edge-sharing PrO6 octahedra are aligned along the c-axis. Na2LnO3 (Ln = Ce, Pr, Tb) crystallizes monoclinically with space group C2/c. The Ln and Na atoms at z ∼ 0.25 and 0.75 are octahedrally coordinated by six oxygen atoms and these octahedra share edges forming slabs in the a–b planes. The resultant Na atoms are located between these slabs. Magnetic susceptibility and specific heat measurements indicate that all of these compounds except for Ce compounds order antiferromagnetically at low temperatures. The Néel temperatures for Li2PrO3, Na2PrO3, and Na2TbO3 are 6.5, 4.6, and 38.3 K, respectively.