Heat capacity and thermodynamic properties of CrSb2 from 5 to 1050 K. Magnetic transition and enthalpy of decomposition

Abstract

The heat capacity of CrSbz has been measured by adiabatic calorimetry from 5 to 991.3 K. At the latter temperature the CrSb,-phase decomposes into the CrSb-phase and an antimonyrich melt. The heat capacity of the two-phase mixture was measured from 991.3 to 1050 K. The heat capacity of CrSb, shows a small sharp h-type transition with a maximum at 274.1 K where the change from the antiferromagnetic to the paramagnetic state occurs. Thelow entropy of the clearly cooperative part of the transition, A& = 0.12 calth K-l mol-I, shows that this contribution is only a small part of the total. From an estimate of the lattice heat capacity of CrSbz outside the h-transition region we find an excess heat capacity amounting to about 1.7 calth K-l mol-l at 300 K, 1.6 calth K-l mol-' at 500 K, and 1.1 calth K-' mol-1 at 800 K, which we attribute to the population of excited electronic states in CrSbz. The total transitional entropy amounts to about 2.6 cal,,, K-l mol-1 at 900 K only slightly more than the R In 3 (= 2.17 calth K-l mol-') expected from randomization of two unpaired spins per chromium atom. The enthalpy of the peritectic decomposition of CrSb, at 991.3 K is (8325120) calth mol-I. The high heat capacity above 991 K is presumably related to the solution of CrSb(s) in the meh. Thermodynamic functions have been evaluated and the values of C,, {S"(T)-s"(O)}, and-{G"(T)-H'(O)]/T at 298.15 K are (19.66*0.02), (27.46*0.03), (14.OO9&0.014) calth K-l mol-I. CrSb, loses antimony on approaching the peritectic temperature and the composition of the decomposing phase is in the range CrSb,,,, to CrSbl.g5. To explore further the homogeneity range of the CrSba-phase some heat-capacity measurements on CrSb1.85 have also been carried out. Combination of the present results with standard Gibbs energies of formation at 850 K from the literature gives for CrSbz.ao: 298.

The effect of Sn substitution for Sb on transport and thermoelectric properties of CrSb2 at low temperatures

“…3), which is well consistent with pervious result reported by other authors [21]. The observed anomaly was proved to originate from antiferromagnetic transition [22,24,28] and the plateau was related to an electronic change of the electron-spin system in the antiferromagnetic semiconductor [29]. In comparison, the resistivity for CrSb 2−x Sn x has a similar temperature dependence, that is, it shows semiconductor-like behavior, and the plateau (as shown in Fig.…”

“…Therefore, the left two unpaired electrons per Cr do not contribute to the bond, CrSb 2 has a d-state manifold per Cr atom 3d 2 in CrSb 6 -octahedra [19,[24][25][26], taking a localized high-spin configuration [20,22,27]. Moreover, CrSb 2 is an antiferromagnetic compound with the Neel temperature of T N = 273 ± 2K [21,22,24,28]. The magnetic properties of Cr 1−x Fe x Sb 2 (0 ≤ x ≤1) was reported by Kjekshus et al [24], which showed that the Neel temperature decreased with increasing Fe content and diminishes to zero at about x = 0.5.…”

Transport, thermal, and magnetic properties of the narrow-gap semiconductor CrSb2

“…The compounds FeSi, FeSb 2 and CrSb 2 are narrow gap semiconductors, Eg ≈ 0.1 eV, with dominant 3dcharacter of the electronic states near the conduction and valence band edges and interesting magnetic and transport properties [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Both CrSb 2 and FeSb 2 crystallize in the orthorhombic marcasite structure (P nnm space group), while FeSi crystallizes in the cubic B20 structure (P 2 1 3 space group).…”

Transport and thermoelectric properties of Cr1−xMnxSb2 at low temperatures

“…4), which is well consistent with pervious result reported by other authors (the observed anomaly for CrSb 2 is around 273 K [18]). The observed anomaly was proved to originate from antiferromagnetic transition [19,21,22] and the plateau was related to an electronic change of the electron-spin system in the antiferromagnetic semiconductor [23]. By comparing curve (a) with curves (b)-(d) in Fig.…”

“…CrSb 2 has the orthorhombic marcasite structure (crystal group Pnnm): each Cr atom has a distorted octahedral coordination of six nearest-neighbor Sb atoms; each Sb atom is tetrahedrally coordinated by three Cr atoms and one Sb atom [16][17][18][19][20]. CrSb 2 is an antiferromagnetic compound with the Neel temperature of T N = 273 ± 2 K [18,19,21,22]. The magnetic properties of Cr 1−x Fe x Sb 2 (0 ≤ x ≤ 1) was reported by Kjekshus et al [21], which showed that the Neel temperature decreased with increasing Fe content and diminished to zero at about x = 0.5.…”