中文摘要：

采用真空熔炼及热压烧结方法制备了Na和Ga共掺杂n型Bi2Te2.7Se0.3热电材料。XRD结果表明,Na0.04Bi1.96-xGaxTe2.7Se0.3块体材料的XRD图谱与Bi2Te2.7Se0.3的图谱对应一致。通过EDAX技术对Na0.04Bi1.96-xGaxTe2.7Se0.3块体材料的成分进行了分析,无氧化现象。在298~523K温度范围内,在垂直于热压方向对样品的电热输运性能进行了测试分析,结果表明Na和Ga共掺杂可以有效地提高Bi2Te2.7Se0.3的载流子浓度,从而使电导率得到明显改善,但同时Seebeck系数有不同程度的损失。由于晶格热导率减小,Na掺杂及共掺杂样品Na0.04Bi1.96-xGaxTe2.7Se0.3（x=0.04）均使热导率降低。当Na掺杂浓度为0.04时,随着Ga掺杂浓度的增加,热导率呈现递增的现象,Na和Ga共掺杂样品Na0.04Bi1.96-xGaxTe2.7Se0.3（x=0.04）的热电优值获得了较明显的提高,在398K时的最大ZT值为0.75。

英文摘要：

Na and Ga co-doped n-type Bi2Te2.7Se0.3thermoelectric materials were synthesized by vacuum melting and hot pressing methods.XRD results indicate that all the characteristic peaks of the bulk Na0.04Bi1.96-xGaxTe2.7Se0.3can be indexed into those of the bulk Bi2Te2.7Se0.3.Compositional analysis of the bulk Na0.04Bi1.96-xGaxTe2.7Se0.3was carried out by energy dispersive analysis of X-rays（EDAX）,in which no oxidation was detected.Electrical and thermal transport properties of the samples had been measured along the the direction perpendicular to the hot-pressing direction in the temperature range of 298-523 K.Na and Ga codoping can enhance the carrier concentration,and accordingly the electrical conductivity as well.The Seebeck coefficients of the co-doped samples have different degree of loss.Due to the decrease of lattice thermal conductivity,Na-doped and Na and Ga co-doped Na0.04Bi1.96-xGaxTe2.7Se0.3（x=0.04）samples can reduce the thermal conductivity.Thermal conductivity of the Na0.04Bi1.96-xGaxTe2.7Se0.3increases gradually with the increase of Ga-doping.Na and Ga co-doped Na0.04Bi1.96-xGaxTe2.7Se0.3（x=0.04）samples lead to a great improvement in the thermoelectric figure of merit ZT.The highest ZT of the sample can reach 0.75 at 398K.