摘要:
利用传统的固相反应法在还原性气氛1200℃下分别制备出不同Nb掺杂量的Ti1-xNbxO2-δ陶瓷样品.样品的粉末X射线衍射（XRD）结果显示：Nb掺杂量x较低时样品为多相混合,当Nb掺杂量x〉0.02时样品为单一的四方相金红石型结构.在室温到900K的测试温区,测试了单相样品（x=0.02,0.03,0.04）的电导率、Seebeck系数和热导率.测试结果表明,样品的电导率和Seebeck系数随温度的变化都表现为非金属性的行为,通过拟合证明了样品在低温区为热激活导电机制,在高温区为小极化子导电机制.对XRD、电导率以及Seebeck系数随Nb掺杂量的变化规律进行分析表明,随着Nb掺杂量的增大,样品中的氧空位逐渐减少.单相样品的热导率都随温度的升高而逐渐降低,以晶格热导为主.在测试温区,x=0.02样品在873K时热电性能最好,其热电优值ZT达到0.19.
Abstract:
Titanium oxide ceramics doped with niobium is synthesized in reduced atmosphere at 1200℃ by conventional solid-state reaction technique.From their crystal structures determined by the powder X-ray diffraction（XRD）,the samples have multiple-phase with low Nb concentration,but they have single tetragonal rutile phase when Nb content is larger than 0.02.The electrical conductivities,the Seebeck coefficients and the thermal conductivities of the samples with single phase are measured at a temperature range between room temperature and 900 K.The electrical conductivity and the Seebeck coefficient show non-metallic behaviors.According to the fitting,it is found that the samples show thermal-activation mechanism at low temperatures and small-polaron hopping conduction mechanism at high temperatures.Moreover,the analyses of XRD,electrical conductivity and Seebeck coefficient show that the concentration of oxygen vacancy decreases with Nb content increasing.Thermal conductivity decreases with temperature increasing,dominating by lattice thermal conductivity.In the measurement region,the figure of merit （ZT） reaches a highest value of 0.19 at 873 K in the Ti0.98Nb0.02O2-δ sample.
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