Synthesis and characterization of KTh2SeE6, KTh2Te6 and CsTh2Se6

Article abstract of DOI:10.1016/S0925-8388(96)02838-1

The compounds KTh₂Se₆, KTh₂Te₆ and CsTh₂Se₆ have been synthesized in the temperature range 873 to 923 K. These compounds are isostructural with the previously synthesized compound CsTh₂Te₆. They crystallize in the space group D¹⁷_2h-Cmcm of the orthorhombic system with two formula units in cells: a=4.14(2) A, b=21.88(4) A, c=5.64(1) A, V=511(4) A³ (T=298 K) for KTh₂Se₆; a=4.356(1) A, b =23.702(7) A, c=6.141(2) A, V=634.1(3) A³ for KTh₂Te₆ (T=113 K); and a=4.14(5) A, b=23.88(4) A, c=5.67(5) A, V=561(13) A³ (T=298 K) for CsTh₂Se₆. The structure of KTh₂Te₆ has been determined from single-crystal X-ray data. The structure is composed of ²∞[Th₂Te^-₆] layers that stack perpendicular to [010]. The layers are separated by K⁺ cations that are coordinated to eight Te atoms at the corners of a rectangular parallelepiped. The K site is one-half occupied. Te atoms form infinite chains within the layers along [001] with Te-Te distances between 3.057(3) A and 3.085(3) A. KTh₂Se₆, KTh₂Te₆ and CsTh₂Se₆ are highly resistive along [100].