original physical properties related to the crystallochemical A solid-state investigation of the Bi 2 O 3 -TeO 2 -WO 3 system behavior of Bi(III) and Te(IV) atoms. This paper describes allowed synthesis of a new stoichiometric compound, Bi 2 the crystal structure of one of these new phases, Te 2 W 3 O 16 (MX 2.286 ). Bi 2 Te 2 W 3 O 16 crystallizes with monoclinic Bi 2 Te 2 W 3 O 16 , and its relationships with the fluorite and symmetry (space group C2/c) with the unit cell parameters Bi 7 O 5 F 11 structures. a β«Ψβ¬ 21.2871(8) A Λ, b β«Ψβ¬ 5.5708(3), c β«Ψβ¬ 12.8349(5) A Λ, β€ β«Ψβ¬ 124.08(3)Ψ, and Z β«Ψβ¬ 4 formula units per cell. The structure EXPERIMENTAL was determined from single-crystal X-ray diffraction data and refined to residuals R 1 (F ) β«Ψβ¬ 0.036 and wR 2 (F 2 ) β«Ψβ¬ 0.089 for 106 Heating in air at 720ΠC for 48 h an intimate mixture of variable parameters and a data set of 1756 observations [I ΟΎ pure commercial Bi 2 O 3 , TeO 2 , and WO 3 oxides (Aldrich, 2(I)]. The essential building units of the structure are BiO 8 square antiprisms, TeO 4 disphenoids, and WO 6 octahedra. Pairs 99.99%) in the molar ratio 1 : 2 : 3 led to the formation, of BiO 8 square antiprisms share one edge to form a Bi 2 O 14 unit. in the solid state and as a green polycrystalline powder, Each Bi 2 O 14 unit shares four corners with four identical Bi 2 O 14 of an original solid phase with the probable formula units, two edges and four corners with W(2)O 6 octahedra, and Bi 2 Te 2 W 3 O 16 . Since no significant change in weight was four edges with TeO 4 disphenoids, so constituting [Bi 2 observed, and since the same solid phase was obtained Te 2 W(2) 2 O 16 ] complex layers parallel to (100). These layers are when the synthesis was performed in a sealed gold tube, connected via W(1)O 6 to form the Bi 2 Te 2 W 3 O 16 three-dimenit was clear that no oxidation of Te(IV) had occurred and sional network. Its relationships with the fluorite structure and that the formula proposed was correct. the fluorite-related Bi 7 O 5 F 11 structure are evidenced and Bi 2 Te 2 W 3 O 16 is stable only below 750ΠC; above this temanalyzed. Β© 1996 Academic Press perature it decomposes into two crystalline phases, WO 3 and Bi 2 W 2 O 9 , and a liquid phase, which on cooling leads to the formation of a ternary glass of unidentified composition.