Untersuchungen zum ternären System Bi/Te/O, II. Thermisches Verhalten und Koexistenzbeziehungen von Bi₂O₂Te/Investigations of the Ternary System Bi/Te/O, II. The Thermal Behaviour and the Relations of Phase Coexistences of Bi₂O₂Te

Abstract

The phase Bi20 2Te exists in the pseudobinary system Bi203/Bi2Te3. The thermal behaviour of Bi2Ö2Te was determined by DTA and X-ray analysis: The phase exists up to 620 °C and decomposes into the solid phases Bi12TeO20, Bi10Te2O 19 [1] and liquid BiTe. The relations of the phase coexistences in the pseudobinary system and in the ternary area Bi20 3/Te02/Bi2Te3/Te were investigated by solid state reactions, chemical transport reactions, and by total pressure measurements.

Synthesis, characterisation and thermoelectric properties of the oxytelluride Bi2O2Te

“…TGA data collected on Bi 2 O 2 Te under an inert atmosphere indicate that the onset of weight loss occurs around 900 K (Fig. 4), which is consistent with the decomposition temperature of 893 K previously reported by Schmidt et al [22].…”

“…Consequently, the figure of merit of the oxytelluride (ZT¼ 0.42 at 373 K) is significantly higher than that of the oxyselenide (ZT ¼0.15 at 373 K) [20,21]. In sharp contrast, the effect of substituting Se by Te in Bi 2 O 2 Se is not known, although the existence of a phase with stoichiometry Bi 2 O 2 Te, together with its thermal stability, have been reported by Schmidt et al [9,22,23]. To the best our knowledge, the thermoelectric properties of Bi 2 O 2 Te have never been investigated.…”

Surface electronic structure of bismuth oxychalcogenides

“…For example, Bi 2 S 2 Se has orthorhombic crystal structure with space group Pnma [41], and the Bi 2 O 2 S crystal has both orthorhombic and tetragonal structures with space group symmetries Pnnm and P4/nmm, respectively [42]. Bi 2 O 2 Se and Bi 2 O 2 Te also present a tetragonal-type lattice but with space group symmetry I4/mmm [43][44][45][46][47].…”

Electron and phonon transport properties of layered Bi2O2Se and Bi2O2Te from first-principles calculations

“…The measured thermal conductivities are low, 3.1 W m −1 K −1 for Bi 2 Se 3 [13] and 2.0 W m −1 K −1 for Bi 2 Te 3 [14]. By the solid state reaction of Bi 2 Se 3 with Bi 2 O 3 and Bi 2 Te 3 with Bi 2 O 3 , the ordered ternary layered bismuth oxide crystalline compounds of Bi 2 O 2 Se and Bi 2 O 2 Te have been synthesized experimentally [15][16][17], and they exhibit a tetragonal structure with I4/ mmm space group and make up of Se/Te atomic layers sandwiched between Bi 2 O 2 layers with weak electrostatic interactions. Ruleova et al [17] experimentally observed that Bi 2 O 2 Se has a low thermal conductivity with 1.1 W m −1 K −1 at room temperature and 0.7-0.75 Wm −1 K −1 at T=800 K. However, the ZT value is only about 0.2 at 800 K due to the low electrical conductivity.…”