Synthesis, crystal structure, and thermoelectric properties of a new layered carbide (ZrC)₃[Al_3.56Si_0.44]C₃

Abstract

A new quaternary layered carbide, (ZrC)3[Al3.56Si0.44]C3, has been synthesized and characterized by x-ray powder diffraction and thermopower and electrical conductivity measurements. The crystal structure was successfully determined using direct methods and further refined by the Rietveld method. The crystal is trigonal (space group R3m*, Z = 3) with lattice dimensions a = 0.331389(7), c = 4.90084(7) nm, and V = 0.46610(1) nm3. The final reliability indices calculated from the Rietveld refinement were Rwp = 9.53% (S = 1.70), Rp = 7.22%, RB = 1.81%, and RF = 0.94%. The crystal structure is composed of the NaCl-type [Zr3C4] slabs separated by the Al4C3-type [Al0.89Si0.11C] layers. This material had thermoelectric properties comparable to the layered carbides (ZrC)2[Al3.56Si0.44]C3 (Zr2[Al3.56Si0.44]C5), (ZrC)2Al3C2, and (ZrC)3Al3C2 in the temperature range of 373–1273 K, with the maximal power-factor value of 6.6 × 10−5 W m−1K−2 at 545 K. The two quaternary carbides have been found to form a homologous series with the general formula of (ZrC)n[Al3.56Si0.44]C3 (n = 2 and 3).

Syntheses and crystal structures of Si-bearing layered carbides ZrAl8C7 and ZrAl4C4

“…Hence, the homologous carbides demonstrated good performance of thermoelectricity, and regarded as the promising thermoelectric materials. 6), 7) In the present study, we have successfully dissolved the Si component into the [Al8C7] layers of (ZrC)mAl8C6 (m = 1 and 2) to stabilize the crystal structures at 2073 K, which is 200 K lower than the formation temperature of the end members.…”

The thermal shock behavior of Zr3[Al(Si)]4C6 and in situ (ZrB2+ZrC)/Zr3[Al(Si)]4C6 composite

“…Zr 3 [Al(Si)] 4 C 6 is a new quaternary layered carbide formed by adding Al and Si to ZrC, which shows superior oxidation resistance, strength, specific stiffness, and toughness to ZrC, especially at elevated temperatures [1][2][3][4]. The Young's modulus of Zr 3 [Al(Si)] 4 C 6 decreases slowly with increasing temperature and at 1600°C it remains 80% of that at ambient temperature [2,5].…”

[Zr0.72Y0.28]Al4C4: A new member of the homologous series (MC)l(T4C3)m (M=Zr, Y and Hf, T=Al, Si and Ge)

“…For the NaCl-type compound ZrC, the unit cell content is [Zr 4 C 4 ], indicating that the existence of the homologous phases with lX4 is thermodynamically improbable [6]. Actually, the mixture of ZrC and (ZrC) 3 Al 4 C 3 was the stable form for the specimens with the bulk chemical compositions of lX4 [1,7]. Accordingly, the maximum value of integer l is limited to 3.…”

“…The [Al 4m C 3m+1 ] layers were incorporated by several amounts of Si [1,[7][8][9] and/or Ge [10] components, whereas considerable amount of Y [11] component dissolved into the [Zr l C l+1 ] layers. Therefore the general formula has to be expanded to (Zr 1Àx Y x-C) l {(Al lÀyÀz Si y Ge z ) 4 C 3 } m , where the maximum x-, y-and z-values were 0.02, 0.07 and 0.02, respectively [1,[7][8][9][10][11].…”

“…Therefore the general formula has to be expanded to (Zr 1Àx Y x-C) l {(Al lÀyÀz Si y Ge z ) 4 C 3 } m , where the maximum x-, y-and z-values were 0.02, 0.07 and 0.02, respectively [1,[7][8][9][10][11]. After the publication of papers on Zr 2 (Al,Si) 4 C 5 [8] and Zr 3 (Al,Si) 4 C 6 [7], the isomorphous crystal structures were reported in the Hf-Al-C system for Hf 2 Al 4 C 5 and Hf 3 Al 4 C 6 [12]. Accordingly, it would be relevant to further expand the solid-solution formula to (MC) l (T 4 C 3 ) m , where M ¼ Zr, Y and Hf, T ¼ Al, Si and Ge.…”