Negative thermal expansion,electrical and mechanical properties of antiperovskite Mn 3 Zn 0.5 A 0.5 N ( A  = Sn,Ag,Ni)

Abstract

Thermal expansion, electrical conductivity, hardness and friction property of Mn₃ZnN, which had been doped with Sn, Ag or Ni and sintered at 1223 K, were measured. X-ray diffraction analyses show that these compounds have a cubic antiperovskite Mn₃CuN-type structure and negative thermal expansion (NTE). The width of NTE operation temperature (ΔT) and the coefficient of thermal expansion are different when Mn₃ZnN was doped with different element. A giant NTE coefficient of −81.00 × 10⁻⁶ K⁻¹ is obtained from Mn₃Zn_0.5Ag_0.5N while ΔT is 18 K. A broad ΔT of 60 K is obtained from Mn₃Zn_0.5Sn_0.5N with thermal expansion coefficient of −19.05 × 10⁻⁶ K⁻¹. The results show that Mn₃Zn_0.5A_0.5N (A = Sn, Ag, Ni) has good electrical conductivity. The electrical conductivity of Mn₃Zn_0.5Ag_0.5N is the largest among these compounds as 2.45 × 10³ S cm⁻¹. The Vickers hardness of these compounds is more than 350 HV. The friction coefficients of Mn₃Zn_0.5Ag_0.5N, Mn₃Zn_0.5Ni_0.5N and Mn₃Zn_0.5Sn_0.5N are 0.5318, 0.4554 and 0.2336, respectively.