Synthese et etude structurale du tellurate (VI) de thallium (III) Tl2TeO6

Phase Formation and Dielectric Characterization of the Bi2O3–TeO2 System Prepared in an Oxygen Atmosphere

“…(B) Bi 2 TeO 6 : Single-phase Bi 2 TeO 6 ceramic powder cannot be sintered to a high-density single-phase ceramic below the decomposition temperature at 730°C. 16,17 The slope of the sintering curve noticeably increases when the decomposition temperature is exceeded (Fig. 7).…”

“…These weak XRD lines could be found in PDF No. 38 -0731, which was published earlier, 16 and was not indexed. To show that the weak lines corresponded to the Bi 6 Te 2 O 15 compound, we indexed the diffraction pattern.…”

“…The structure exhibits some similarities with MTe 3 O 8 compounds (M ϭ Ti, Zr, Hf, Sn), among which the titanium analogue has been later reported to have interesting microwave dielectric properties. 15 Frit et al 16 have reported on the formation and the crystal structure of an orthorhombic-Bi 2 TeO 6 compound prepared under an oxygen atmosphere, and they have discovered similarities with tungsten and molybdenum analogues. Furthermore, they also have reported the existence of a Bi 6 Te 2 O 15 compound with an orthorhombic unit cell and have suggested it is thermally stable up to 850°C under oxygen.…”

“…18 A further review of studies on the Bi 2 O 3 -TeO 2 system reveals several inconsistencies. Room-temperature phases Bi 12 TeO 20 and Bi 16 Te 5 O 34 are reported to have been prepared under vacuum; 8 however, neither of the phases is included in the corresponding phase diagram. 7 Next, the oxidation of Bi 2 TeO 5 to Bi 2 TeO 6 has been suggested to occur under air, 19 although Bi 2 TeO 6 cannot be found in the Kikuchi phase diagram.…”