화학공학소재연구정보센터
Inorganic Chemistry, Vol.46, No.8, 3231-3235, 2007
New layered germanide halides RE2GeX2 (RE = Y, Gd; X = Br, I)
The title compounds were synthesized from RE, REX3, and Ge under an Ar atmosphere at 1200-1370 K. Y2GeI2 and Gd2GeI2 crystallize in space group R (3) over barm with lattice constants a = 4.2135(3) and 4.2527(1) angstrom and c = 31.480(2) and 31.657(1) angstrom, respectively. Gd2GeBr2 crystallizes in two modifications, the 1T-type (space group P (3) over bar m1; a = 4.1668(2) angstrom, c = 9.8173(6) angstrom) and the 3R-type (space group R (3) over barm; a = 4.1442(9) angstrom, c = 29.487(7) angstrom). The structural motifs of RE2GeX2 compounds are Ge-centered slightly distorted RE6 octahedra connected via their common edges and extending in the a and b directions. The resulting close-packed double layers are separated by halogen atoms. The electrical resistivity measurements revealed semiconductor behavior for Y2GeI2 and Gd2GeI2 and a metal-semiconductor transition for 1T-Gd2GeBr2. Magnetic susceptibility and heat capacity measurements show long-range magnetic ordering for Gd2GeI2 and 1T-Gd2GeBr2 at similar to 15 and similar to 13 K, respectively.