The influence of boron addtion on structural, magnetic and thermoelectric properties of Ni₂Mn_1.52Sb_0.48B_x

Heusler alloys known as X₂YZ (full­-Heusler) and XYZ (half-­Hersler), where X and Y denote the transition metals and X is s-­p such as Al, Ga, Sb, Sn, In, ect., have been extensively studied since they possess many important properties [1-­3] like shape memory effect, magnetocaloric effect (MCE), magnetoresistance and thermoelectric effect. In this work, structure, magnetic and thermoelectric properties of the full­-Hersler Ni₂Mn_1.52Sb_0.48 alloy were investigated in terms of Boron (B) addition. We have found that the structural transition temperature i.e. the ferromagnetic­to­antiferromagnetic martensitic transition (TM) decreases, while the paramagnetic­ferromagnetic austenitic transition (TC) tends to increase with increasing B concentration. Temperature dependent X­ray diffraction patterns from 200 ­- 500 K clearly shows an evolution of the structural transformation from orthorhombic to cubic structure. It was interestingly found in the high­temperature (300 -­ 1000 K) thermoelectric properties, that the sample with x = 1 switches from n­-type conducting behavior at temperatures below 570 K to p-­type conducting one in higher temperature region. However, with higher B concentration e.g. x = 2, the sample shows n-­type conducting behavior over the whole measured temperature range, again confirming the effect of boron addition.