【摘要】 采用固相反应法制备铜铁矿结构的CuAl_1-xMg_xO₂（x=0、0.005、0.01、0.02、0.03、0.04）多晶，研究了Mg掺杂对CuAlO₂多晶结构和性能的影响。Mg掺杂量x从0增加到0.02,样品均为菱方R3m单相，密度依次提高；所有样品呈半导体的热激活电输运行为，x=0.02样品在室温下的电阻率是未掺杂样品的1/19,热激活能显著下降(x=0时，ρ_{300 K}～5.54Ω·m,E_a～0.328 eV;x=0.02时，ρ_{300 K}～0.29Ω·m,E_a～0.218 eV),载流子浓度增加1个量级，主要因为Mg²⁺取代Al³⁺,引入新的受主能级。x>0.02时，MgAl₂O₄尖晶石杂相出现，使其电导率和热导率降低。CuAl_1-xMg_xO₂多晶的晶格热导率在总热导率中占绝对优势，且随温度升高（300～500 K）而下降，晶格热导Callaway模型模拟表明，所有样品的热阻主要源于点缺陷-声子散射。与x=0相比，x=0.02样品的室温热导率增大1倍（κ～13.065 0 W/（m·K））,声速增大，点缺陷-声子散射减弱，分析认为掺Mg形成强的Mg—O键，提高了晶体的弹性模量和声子频率，减弱了本征点缺陷、Mg掺杂引起的质量波动和应变场波动对声子的散射，同时Mg掺杂样品的密度提高也有利于增加热导率。更多还原

【Abstract】 The CuAl_1-xMg_xO₂（x=0, 0.005, 0.01, 0.02, 0.03, 0.04） polycrystals with delafossite structure were prepared by solid state reaction. The effects of Mg doping on structure and properties of CuAlO₂ polycrystals were studied. With the Mg doping amount x increasing from 0 to 0.02, the samples are of rhombohedral single phase with the space group of R3m, and density increases gradually. All samples exhibit the thermally activated electrical transport behavior of semiconductor, for x=0.02 sample, the room temperature resistivity is 1/19 of undoped sample, and the thermal activation energy decreases significantly(x=0, ρ_{300 K} ～5.54 Ω·m, E_a～0.328 eV; x=0.02, ρ_{300 K}～0.29 Ω·m, E_a～0.218 eV), the carrier concentration increased by 1 order of magnitude, as a result of the Al³⁺ is substituted by Mg²⁺, the new acceptor energy level is introduced. When x is greater than 0.02, the impurity phase of spinel MgAl₂O₄ increases, which leads to the drop of electrical conductivity and thermal conductivity. The lattice thermal conductivities of CuAl_1-xMg_xO₂ polycrystals are absolutely dominant in total thermal conductivity, and decrease as the temperature（300～500 K） increases. The simulation results of the Callaway model demonstrate that the point defect-phonon scattering makes a major contribution to thermal resistance of all samples. Compared with x=0, the room temperature thermal conductivity is doubled（κ～13.065 0 W/（m·K））, while the sound velocity increases and the point defect-phonon scattering weakens when x=0.02. The analysis shows that the strong Mg—O bond is formed by Mg-doping, which improves the elastic modulus of crystal and the phonon frequency, while the scattering between point defects and phonon is weakenes, the point defects include intrinsic point defect, the mass fluctuation and strain field fluctuation caused by Mg doping. The increase of density by Mg doping is also beneficial for thermal conductivity.更多还原