Sr掺杂对CaMnO_3基氧化物电子性质及热电输运性能的影响

采用密度泛函理论计算分析的方法研究了Ca位Sr掺杂的CaMnO_3基氧化物的电子性质和电性能;采用柠檬酸溶胶-凝胶法结合陶瓷烧结制备工艺制备了Ca位Sr掺杂的CaMnO_3基氧化物块体试样,分析研究了所得试样的热电传输性能.结果表明,Sr掺杂CaMnO_3氧化物仍然呈间接带隙型能带结构,带隙宽度由0.756 eV减小到0.711 eV.Sr掺杂CaMnO_3氧化物费米能级附近的载流子有效质量均得到调控,载流子浓度也有所增大.Sr比Ca具有更强的释放电子能力,其掺杂在CaMnO_3氧化物中表现为n型.Sr掺杂的CaMnO_3基氧化物材料电阻率大幅度降低,Seebeck系数绝对值较本征CaMnO_3基氧化物材料有一定程度的增大,Sr掺杂量为0.06和0.12的Ca_(1-x)Sr_xMnO_3(x=0.06,0.12)试样,其373 K的电阻率分别降低至本征CaMnO_3基氧化物材料的25%和21%,其373 K的Seebeck系数绝对值分别是本征CaMnO_3基氧化物材料的112.9%和111.1%,Sr掺杂有效提高了CaMnO_3基氧化物材料的热电性能.

Effects of Sr doping on electronic and thermoelectrical transport properties of CaMnO3 based oxide

The electronic and the electrical properties of the Sr doped CaMnO₃ oxide for Ca site are studied by the density funtional theory calculation method. The Sr doped CaMnO₃ oxide bulk samples are prepared by the citrate acid sol-gel method as well as the ceramic preparation method, and the thermoelectric transport properties are analyzed. The results show that the Sr doped CaMnO₃ oxide still has the indirect band gap yet with the band gap energy slightly decreasing from 0.756 eV to 0.711 eV. The effective mass of carrier near Fermi level is modified and the carrier density near Fermi level is also increased. The ability to release electrons of Sr is stronger than that of the Ca, and the Sr acts as n-type donor doping specy within the CaMnO₃ compound. The electrical resistivity values remarkably decrease for the Sr doped CaMnO₃ oxide materials. The Seebeck coefficient increases slightly to a certain extent compared with that of the intrinsic CaMnO₃. The resistivity values for the Ca_1-xSr_xMnO₃ (x=0.06, 0.12) samples at 373 K decrease to 25% and 21% of the un-doped intrinsic CaMnO₃ sample, respectively. The Seebeck coefficients for the Ca_1-xSr_xMnO₃ (x=0.06, 0.12) samples at 373 K increase to as high as 112.9% and 111.1% of the Seebeck coefficient for un-doped intrinsic sample, respectively. The thermoelectric performance is effectively enhanced by Sr doping for the CaMnO₃ oxide material.