The relationship between the crystal structure and electrical properties of K2NiF4-type (Ca2−xNdx)MnO4

• (Ca2−xNdx)MnO4 was synthesized using the polymerizable complex method.
• The Mn–O(2) distance increased with x.
• The samples were n-type semiconductors and exhibited hopping conductivity.
• The carrier concentration increased slightly, whereas mobility decreased 20% with x.
• Electrical conductivity was affected by the electron transfer and the Mn–O distance.

K2NiF4-type (Ca2−xNdx)MnO4 synthesized using a polymerized complex route crystallized in a tetragonal structure with space group I41/acd in the range of 0 ≤ x ≤ 0.2 and crystallized in an orthorhombic structure with space group Fmmm in the range of 0.3 ≤ x ≤ 0.4. The Mn–O(2) distance of the a- and b-axis directions increased with values of x. The samples were n-type semiconductors and exhibited hopping conduction in a small-polaron model at temperature greater than 393 K. At room temperature, the carrier concentration increased slightly, whereas mobility decreased by 20% with increasing x values. The absolute value of the Seebeck coefficient monotonously increased with temperature and abruptly decreased with increasing values of x at a given temperature. These results indicated that electrical conductivity was strongly affected by the antagonism of the electron transfer in the Mn4+–O–Mn3+ path and the overlap between the Mnt2g and Opπ orbitals.

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