P掺杂β-FeSi_(2)材料的制备与热电输运性能

Preparation and Thermoelectric Transport Properties of P-doped β-FeSi_(2)

β-FeSi_(2)作为一种绿色环保、高温抗氧化的热电材料,在工业余热回收领域具有潜在的应用价值。虽然磷(P)是一种理想的β-FeSi_(2)硅(Si)位的n型掺杂元素,但是P掺杂β-FeSi_(2)易出现第二相,从而限制了其热电性能的提升。本研究采用感应熔炼法合成了一系列FeSi_(2)-xPx(x=0,0.02,0.04,0.06)样品,极大程度地避免了第二相的产生,并系统研究了P掺杂对β-FeSi_(2)热电输运性能的影响。结果表明,P在β-FeSi_(2)中的掺杂极限约为0.04,与前期的理论缺陷计算结果相符。此外,P掺杂优化了β-FeSi_(2)的热电性能,在850 K时,FeSi1.96P0.04的最高热电优值ZT约为0.12,远高于已有的研究结果(673 K,最高ZT仅为0.03)。然而,与同为n型Co和Ir掺杂的β-FeSi_(2)相比(其载流子浓度可达10^(22)cm^(-3)),P掺杂β-FeSi_(2)的载流子浓度较低,最高仅为10^(20)cm^(-3),这导致其电声散射效应较弱,从而限制了整体热电性能的提升。若能提高其载流子浓度,则热电性能有望得到进一步提升。

β-FeSi_(2),an environmentally friendly and high temperature oxidation-resistant thermoelectric material,has potential applications in the field of industrial waste heat recovery.Previous studies have shown that phosphorus(P),an ideal n-type dopant in the silicon(Si)site ofβ-FeSi_(2),can easily lead to the formation of a secondary phase,thereby limiting the enhancement of thermoelectric performance.In this study,a series of FeSi_(2)-xPx(x=0,0.02,0.04,0.06)samples were synthesized using an induction melting method,which greatly inhibited the formation of the secondary phase.Then,the influence of P doping on the electrical and thermal transport properties ofβ-FeSi_(2)was studied.The results indicate that the solubility limit of P inβ-FeSi_(2)is about 0.04,consistent with earlier theoretical predictions based on the defect formation energy.It is also discovered that P doping enhanced the thermoelectric performance ofβ-FeSi_(2),culminating in an optimal figure of merit(ZT)of FeSi1.96P0.04 approximately 0.12 at 850 K,which is much higher than the previous results(ZT about 0.03 at 673 K).However,compared toβ-FeSi_(2)doped with other n-type elements like cobalt(Co)and iridium(Ir),which can achieve carrier concentrations up to 10^(22) cm^(-3),P-dopedβ-FeSi_(2)exhibits lower carrier concentrations,with the highest of only 10^(20) cm^(-3).This results in a weaker electron-phonon scattering effect,which in turn constrains the overall enhancement of the thermoelectric performance.If the carrier concentration could be further increased,the thermoelectric performance of the material is expected to evolve significantly.