The dependences of electrical conductivity, the Hall coefficient, the Seebeck coefficient, thermoelectric power factor and microhardness of Bi₂Se₃ polycrystals on the degree of deviation from stoichiometry 59.9–60.0 at. % Se and temperature (77–300 K) were obtained. The samples exhibited n-type conductivity in the studied ranges of compositions and temperatures. The boundaries of the Bi₂Se₃ homogeneity region were estimated. A non-monotonic behavior of the concentration dependences of the properties in the studied composition range, associated with a change in the phase composition and defect structure under the deviation from stoichiometry, was observed. The calculation of the power coefficient in the temperature dependence of electron mobility showed that in a stoichiometric Bi₂Se₃, electrons are predominantly scattered by acoustic phonons, and under the deviation from stoichiometry the contribution of impurity scattering increases. Based on the experimental data, the Fermi energy E_F was calculated in the approximation of the relaxation time and within the framework of the single-band model with a quadratic dispersion law. The obtained values of E_F showed that both in stoichiometric and non- stoichiometric Bi₂Se₃, the conduction is mainly due to electrons in the lower conduction subband.

中文翻译：

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化学计量比的偏差对Bi2Se3多晶体输运和力学性能的影响

Bi ₂ Se ₃多晶体的电导率，霍尔系数，塞贝克系数，热电功率因数和显微硬度与化学计量比的偏离度为59.9–60.0 at。获得了％Se和温度（77–300 K）。在所研究的组成和温度范围内，样品表现出n型电导率。Bi ₂ Se ₃的边界估计均质区域。观察到在所研究的组成范围内特性的浓度依赖性的非单调行为，与在偏离化学计量的情况下相组成和缺陷结构的变化有关。根据电子迁移率的温度依赖性进行功率系数的计算表明，在化学计量比的Bi ₂ Se _3中，电子主要被声子散射，并且在偏离化学计量比的情况下，杂质散射的贡献增加。根据实验数据，费米能量E _F在弛豫时间的近似范围内，并且在具有二次方差定律的单频带模型的框架内计算出Δε。所获得的E _F值表明，在化学计量比Bi ₂ Se ₃和非化学计量比Bi ₂ Se _3中，传导主要是由于较低传导子带中的电子引起的。