Synthesis of new lead‐containing MAX phases of Zr3PbC2 and Hf3PbC2.

In this work, two new 312 MAX phases of Zr3PbC2 and Hf3PbC2 were successfully synthesized by spark plasma sintering. It is the first discovery of lead‐containing 312 MAX phases, which together with M2PbC (M = Ti, Zr, Hf) form the lead‐containing MAX phase family. Considering the extremely low electrical conductivity of Hf2PbC, these two new compounds are of great research value. Based on the Rietveld refinement results, their lattice parameters and atomic positions were well determined, as a = 3.3771(5) Å, c = 20.0070(9) Å for Zr3PbC2 and a = 3.3357(1) Å, c = 19.7659(8) Å for Hf3PbC2, where M atoms are located at (0, 0, 0) and (1/3, 2/3, 0.1258(6)[Zr]; 0.1255(2)[Hf]), Pb atoms are located at (0, 0, 1/4), and C atoms are located at (1/3, 2/3, 0.0663(2)[Zr]; 0.0641(3)[Hf]), respectively. Additionally, the typical laminar microstructure of Zr3PbC2 and Hf3PbC2 grains was observed. [ABSTRACT FROM AUTHOR]