10.1016/j.scriptamat.2016.03.010
A novel chemical process of Bi2Te2.7Se0.3 nanocompound for effective adjustment in transport properties resulting in remarkable n-type thermoelectric performance
Bismuth shots (Bi, Kojundo Chemical, 99.99%, 2-5 mm) dissolve in diluted nitric acid (2.5 M HNO3(aq)) to subsequently form a transparent solution, which showed signs of bismuth oxidation to generate bismuth ions (Bi3 +) and nitrate (NO3-). Tellurium powders (Te, Kojundo Chemical, 99.99%, 45 μm) do not dissolve in HNO3 but they turn to white precipitates, indicative of tellurium oxidation to form tellurous acid (H2TeO3), which is one of the most stable Te oxoacids. When exposing the reactant elements to HNO3 simultaneously, we observed an entirely different phenomenon; the Te powders gradually dissolved with the Bi shots, resulting in a transparent solution. We assumed that the Te was oxidized by NO3- from the Bi oxidation instead of HNO3, and thus tellurite (TeO32 -) might form rather than H2TeO3 (Eq. (1)) -- a small portion of Te was replaced with selenium powders (Se, Kojundo Chemical, 99.9%, 75 μm) to prepare a ternary compound.
Bismuth shots (Bi
99.99%
%
Bismuth shots
dissolve
2-5 mm
mm
HNO3(aq)
diluted
2.5 M
M
Tellurium powders (Te
99.99%
%
Tellurium powders
45 μm
μm
selenium powders (Se
99.9%
%
selenium powders (Se
75 μm
μm