SYNTHESIS, STRUCTURE, AND PROPERTIES OF SR2CUO2CL2

Syntheses of single-crystal specimens and single-phase polycrystalline samples of Sr2CuO2Cl2 are reported. Differential-thermal-analysis measurements indicate that this compound melts incongruently at 990°C in air and at 970°C in helium. Rietveld refinement of powder neutron diffraction data confirms the body-centered-tetragonal (I4/mmm) K2NiF4-type structure found earlier using x-ray techniques by Grande and Müller-Buschbaum. The CuO2 planes are the same as in (tetragonal) La2CuO4, but the out-of-CuO2-plane oxygens in the latter are replaced by Cl. The temperature dependences of the lattice parameters and thermal factors are reported; the tetragonal structure is retained from 300 K down to at least 25 K. Electrical-resistivity measurements exhibit essentially insulating behavior near room temperature, with ab3000 cm and c6.5×105 cm. © 1990 The American Physical Society.