Abstract:Mg_1-xM_xB₂(M=Li or deficiency) compounds were prepared and their structure and superconducting properties were studied. The results show that nearly single-phased Mg_1-xLi_xB₂ samples have been obtained while x≤0.3. With increasingx, lattice parameters a decreases and c shows no obvious change, and the superconducting transition temperature T_c of Mg_1-xLi_xB₂ decreases. Moreover, loss of superconductivity occurs for sample with x=0.5. For Mg_1-xB₂ nearly single-phased samples can be obtained at x=0. MgB₂ coexists with MgB₄ phase and some minor impurity phases while 0＜x＜0.5. With the increase of x, a and c of MgB₂ decreases and increases, respectively, and T_c decreases. The obvious difference in the superconductivity of Mg_1-xLi_xB₂ and Mg_1-xB₂ suggests that Li indeed dopes into the structure of MgB₂.

Key words: Mg_1-xLi_xB₂; Mg_1-xB₂; lattice parameter; superconducting transition temperature