硅酸盐学报2025，Vol.53Issue(4)：742-747,6.DOI:10.14062/j.issn.0454-5648.20240639
Dy和Nb双掺杂优化CaTiO3材料热电性能
Optimization of Thermoelectric Performance of CaTiO3-Based Materials by Dy/Nb Co-Doping
摘要
Abstract
Introduction CaTiO3-based compounds emerge as a promising thermoelectric material due to their environmentally benign,thermally stable,and cost-efficient merits.Nonetheless,pristine CaTiO3 manifests inherently inferior electronic transport properties.In this paper,Ca1-xDyxTi0.95Nb0.05O3(x=0-0.15)bulk ceramics were prepared via solid-phase sintering combined with hot-pressing sintering,and the composition,microstructure,and thermoelectric properties were analyzed.The results show that Dy and Nb doping can significantly increase the carrier concentration and effectively improve the electronic transport properties.Also,the lattice thermal conductivity is drastically reduced due to the introduction of large mass-field strain and stress-field strain,thus scattering high-frequency phonons.Ca0.85Dy0.15Ti0.95Nb0.05O3 bulk ceramic has a zT maximum of 0.29 at 1073 K,showing that the CaTiO3-based materials have a promising prospect for thermoelectric applications. Methods Ca1-xDyxTi0.95Nb0.05O3(x=0-0.15)bulk ceramics were synthesized by solid-phase sintering and hot pressing.First,powders of CaCO3,Nb2O5,Dy2O3,and TiO2 were mixed and ground in a planetary ball mill for 12 h,then dried and cold-pressed.The pre-burned samples were ground for 6 h and the dried powders were cold-pressed again.The pressed samples were then placed in a graphite mold with a diameter of 13 mm for hot pressing at 1573 K for 1.5 h to obtain dense disks with a thickness of 2 mm. The phase composition of the bulk samples was performed by a model EMPYREAN X-ray diffractometer(XRD,PANalytical Co.,the Netherlands).The elemental distribution of the samples was measured by a model JXA-8530F electron probe X-ray micro-analyzer(EPMA,JEOL Co.,Japan).The Seebeck coefficient and resistivity of the samples were measured simultaneously by a model LSR-3 device(Linseis Co.,Germany).The samples used for the test were long strips with the sizes of approximately 11.0 mm × 2.0 mm × 2.5 mm.The carrier concentration and Hall mobility of the system were measured by a model 8400 Hall measurement system(Lake Shore Co.,Ltd.,USA).The thermal conductivity of the system was measured by a model LFA-457 laser flash thermal conductivity meter(Netzsch Co.,Germany),and the specific heat capacity of the bulk samples was calculated according to the Debye-Dulong law. Results and discussion The polycrystalline Ca1-xDyxTi0.95Nb0.05O3(x=0-0.15)samples with a single phase were prepared.The main phase of the synthesized samples is an orthorhombic structure,with a space group of Pnma.Dy3+and Nb5+occupy Ca2+and Ti4+sites in the matrix,respectively,causing the lattice expansion and introducing the donor impurity levels,transforming CaTiO3 from an insulating wide-bandgap semiconductor to a good electrical conductivity thermoelectric material.The actual amounts of elements Dy and Nb in the bulk samples are basically consistent with the nominal doping concentrations,indicating that elements Dy and Nb are incorporated into the CaTiO3 matrix effectively.The electrical conductivity decreases with increasing temperature,while the absolute value of the Seebeck coefficient increases with increasing temperature,showing typical characteristics of degenerate semiconductor electron transport.At high temperatures,the lattice vibrations are violent,and the acoustic wave scattering dominates the carrier transport,with other scattering mechanisms having little effect on the electronic transport properties.As Dy concentration increases,the effective mass of the density of states decreases.When x=0.15,the maximum zT value can reach 0.29 at 1073 K,which is comparable to the others reported CaTiO3 based thermoelectric performances in the literature. Conclusions Polycrystalline Ca1-xDyxTi0.95Nb0.05O3(x=0-0.15)samples with a single phase were prepared by solid-phase reaction combined with HP sintering.Dy and Nb doping could significantly increase the carrier concentration and effectively improve the electronic transport performance.Meanwhile,the high-frequency phonons were scattered due to the large mass difference and covalent radius difference between Dy3+and Ca2+,resulting in a substantial reduction in the lattice thermal conductivity of the system.Ca0.85Dy0.15Ti0.95Nb0.05O3 achieved the maximum zT value of 0.29 at 1073 K due to the simultaneous optimization of electrical and thermal properties,indicating that CaTiO3 oxide thermoelectric materials could have a promising prospect for thermoelectric applications.关键词
钛酸钙热电材料/电导率/晶格热导率/热电优值Key words
calcium titanate thermoelectric material/electrical conductivity/lattice thermal conductivity/figure of merit分类
通用工业技术引用本文复制引用
蒋全伟,田震,李建波,史晓伟,康慧君,王同敏..Dy和Nb双掺杂优化CaTiO3材料热电性能[J].硅酸盐学报,2025,53(4):742-747,6.基金项目
国家自然科学基金(52271025,51927801). （52271025,51927801）
