Synthesis of new lead‐containing MAX phases of Zr 3 PbC 2 and Hf 3 PbC 2

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In this work, two new 312 MAX phases of Zr 3 PbC 2 and Hf 3 PbC 2 were successfully synthesized by spark plasma sintering. It is the first discovery of lead‐containing 312 MAX phases, which together with M 2 PbC (M = Ti, Zr, Hf) form the lead‐containing MAX phase family. Considering the extremely low electrical conductivity of Hf 2 PbC, 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 Zr 3 PbC 2 and a = 3.3357(1) Å, c = 19.7659(8) Å for Hf 3 PbC 2 , 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 Zr 3 PbC 2 and Hf 3 PbC 2 grains was observed.