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We have successfully synthesized La1.8-xEu0.2SrxCuO4 (x = 0 and 0.05) with the Nd2CuO4-type (T'-type) structure by means of the structural transformation at low temperatures from the K2NiF4-type (T-type) structure via the Sr2CuO3-type (S-type) structure. Superconductivity has appeared by postannealing T'-La1.8-xEu0.2SrxCuO4 in vacuum at 700 °C for the removal of excess oxygen. The superconducting transition temperatures are 20 and 13 K for x = 0 and 0.05, respectively. T'-La1.8-xEu0.2SrxCuO4 with x = 0.05 is, at least nominally, the first hole-doped superconducting cuprate with the T'-type structure.

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Polycrystalline Cr(Si1− x Ge x )2 samples were prepared using arc melting and spark plasma sintering methods. Single-phase Cr(Si1− x Ge x )2 samples were obtained for the compositional range of 0 ≤ x ≤ 0.015 and the lattice parameters monotonically increased with x. In the range of single phases, the electrical conductivity and Seebeck coefficient increased and decreased with increasing x, respectively. The partial substitution of Ge effectively reduced the thermal conductivity to ∼80%, which resulted in the increase in the ZT of Cr(Si1− x Ge x )2 samples from 0.16 (x = 0) to 0.25 (x = 0.015) at 600 K. From the results of first-principles calculation for transport properties, it can be concluded that the origin of the increase in electrical conductivity and the decrease in Seebeck coefficient of Ge-substituted samples is the decrease in carrier effective mass.

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