Phase stability of ScN-based solid solutions for thermoelectric applications from first-principles calculations

Abstract

We have used first-principles calculations to investigate the trends in mixing thermodynamics of ScN-based solid solutions in the cubic B1 structure. 13 different Sc1−xMxN (M = Y, La, Ti, Zr, Hf, V, Nb, Ta, Gd, Lu, Al, Ga, In) and three different ScN1−xAx (A = P, As, Sb) solid solutions are investigated and their trends for forming disordered or ordered solid solutions or to phase separate are revealed. The results are used to discuss suitable candidate materials for different strategies to reduce the high thermal conductivity in ScN-based systems, a material having otherwise promising thermoelectric properties for medium and high temperature applications. Our results indicate that at a temperature of T = 800 °C, Sc1−xYxN; Sc1−xLaxN; Sc1−xGdxN, Sc1−xGaxN, and Sc1−xInxN; and ScN1−xPx, ScN1−xAsx, and ScN1−xSbx solid solutions have phase separation tendency, and thus, can be used for forming nano-inclusion or superlattices, as they are not intermixing at high temperature. On the other hand, Sc1−xTixN, Sc1−xZrxN, Sc1−xHfxN, and Sc1−xLuxN favor disordered solid solutions at T = 800 °C. Thus, the Sc1−xLuxN system is suggested for a solid solution strategy for phonon scattering as Lu has the same valence as Sc and much larger atomic mass.<p>Funding Agencies|Swedish Research Council (VR)|621-2009-5258621-2012-4430621-2011-4417|Linnaeus Strong Research Environment LiLi-NFM||Swedish Foundation for Strategic Research||Linkoping Center in Nanoscience and technology (CeNano)||</p

Microstructure and thermoelectric properties of CrN and CrN/Cr2N thin films

“…Nitride thin films (and other thermoelectric material) can be optimized by adding dopants, synthesizing semiconductor/metal multilayers and nanostructuring, leading to the simultaneous decrease of the electrical resistivity and the thermal conductivity [25,26] and resulting an improved thermoelectric performance (or figure-of-merit). The interest in using thermoelectrics based on early trans itionmetal nitrides is further underlined by the results on ScN-based materials, both pure ScN [27][28][29][30][31], ScN-based solid solutions and alloys [32][33][34], and superlattices [35][36][37].…”

Theoretical study of phase stability, crystal and electronic structure of MeMgN2 (Me = Ti, Zr, Hf) compounds

“…The Seebeck coefficient of ScN is relatively large (reaching -180 lV=K at 800 K) and because of its low electrical resistivity, large power factors between 2.5 and 3.5 9 10 -3 Wm À1 K À2 have been reported [9,10]. Doping and alloying ScN with heavy elements [11,12] and/or creating artificial layer interfaces such as metal/semiconductor superlattices [13][14][15][16] can alter properties and decrease the thermal conductivity, resulting in an enhanced zT.…”

Reduction of the thermal conductivity of the thermoelectric material ScN by Nb alloying

“…2,20 Several approaches to reduce the thermal conductivity in transition metal nitrides have been suggested like nanoinclusions, doping and superlattices. [21][22][23][24][25] Another proposed approach to reduce the thermal conductivity in ScN thin films is to increase the lattice phonon scattering by alloying ScN with different transition metals. Kerdsongpanya et al 22 performed first principles calculations of phase stability on a series of possible alloying elements with ScN.…”

“…[21][22][23][24][25] Another proposed approach to reduce the thermal conductivity in ScN thin films is to increase the lattice phonon scattering by alloying ScN with different transition metals. Kerdsongpanya et al 22 performed first principles calculations of phase stability on a series of possible alloying elements with ScN. One of the suggested alloying elements was niobium for two reasons: (1) …”