LAUSR

Abstract The new ternary compounds Na 1.5 Te 2 Mo 0.5 O 6.25 and K 6 (Te 9 4+ Te 6+ )Mo 6 O 42 have been revealed by the study of the phase relation in the systems Na 2 O–TeO 2 –MoO 3 and K 2 O–TeO 2 –MoO 3 . The structure of the compounds has been investigated by X-ray Single-Crystal Analysis. The Na 1.5 Te 2 Mo 0.5 O 6.25 compound belongs to anti-glass tellurium phase with fluorite-type structure and space group F m 3 ‾ m , Z  = 1, a  = 5.4087 A, where the oxygen atoms are strongly disordered near the 8a site. The K 6 (Te 9 4+ Te 6+ )Mo 6 O 42 mixed-valence tellurium compound possesses trigonal space group P 3 ‾ , Z  = 1, a  = 12.0074 A, c  = 7.8979 A. The K 6 (Te 9 4+ Te 6+ )Mo 6 O 42 structure contains rare units of two [TeO 6 ] octahedron sharing three common oxygen. The decomposition temperatures are 378 °C and 410 °C for Na 1.5 Te 2 Mo 0.5 O 6.25 and K 6 (Te 9 4+ Te 6+ )Mo 6 O 42 , respectively.