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Valence electrons in antimony7/2/2023 ![]() The obtained powder was pressed into a pellet followed by calcination in the electric furnace under the same conditions, and obtained sample was denoted by NAT-NS. The remaining calcined powder was washed by HNO 3 (5.0 mol/L, Kanto Kagaku), then dried at 90˚C for 20 h. The partial calcined powder was uniaxially pressed into a rectangular pellet with the dimensions ~ 4 ´ 5 ´ 20 mm, followed by calcination in an electric furnace (HPM-1N, AS-ONE) in air at 900˚C for 2 h (denoted by NS). The raw materials were weighed to the stoichiometric molar ratio, and were mixed by ball milling (200 rpm, milling rate) for 20 h, and then the mixed powder was calcined at 900˚C for 2 h. In addition, the existence of metallic silver and the ratio of Sb 3+/Sb 5+ in AgSbO 3 are discussed in connection with σ, S, and κ.ĪgSbO 3 was synthesized by SSR using Ag 2O (>99.0%, Kanto Kagaku) and Sb 2O 3 (>98.0%, Kanto Kagaku) as raw materials. Thus, in the present paper, we characterize the AgSbO 3 in details, prepared by the combination of a solid state reaction (SSR) method and a nitric acid (HNO 3) treatment. Moreover, the valency of Sb (Sb 3+ (4d 10), Sb 5+ (4d 105s 2)) should affect s due to generation of oxygen vacancy in the presence of Sb 3+ however such discussion has not been performed. However, the previous studies, regarding TE properties of AgSbO 3, did not mention the existence of metallic Ag. According to Wiggers et al., aggregated Ag islands are formed in the thermally treated AgSbO 3, causing the increase in s by the electron hopping between such metallic islands. So, AgSbO 3 has been investigated as a candidate n-type TE material, e.g., by addition of CuO and by using a spark plasma sintering (SPS) method to prepare dense AgSbO 3. In addition, AgSbO 3 has low stacking density and thus its κ ph is significantly lower than those of other oxides. Different from these oxides, silver antimonite (AgSbO 3), which has a defect pyrochlore structure composed of linear chains of AgO 6 and SbO 6, possesses rather high m originating from its highly-dispersed valence band and conduction band composed of Ag 5s and Sb 5s orbitals, respectively. ![]() It is known that typical oxides have a low mobility (m) and high κ (particularly, κ ph, which is the thermal conductivity mediated by phonons), originating from their ionic bonding between light atoms and high electronegativity of oxygen. From these equations, large S and σ values and a low κ are necessary for high TE performance. TE conversion efficiency is represented by a dimensionless figure of merit, ZT = S 2σT/κ, where S, σ, κ, and T are the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. Recently, several oxides have been recognized as potential thermoelectric materials. Thermoelectric (TE) materials have been attracting attention due to their potential for recycling energy using exhausted heat through the thermal-electric conversion effect, generating clean energy without polluting the environment.
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