paper

One-step synthesis of Cu-doped Pb $_{10}$ (PO $_{4}$ ) $_{6}$ Cl $_{2}$ apatite: A wide-gap semiconductor

arXiv:2406.17239 · doi:10.1039/D4QI01140F

Abstract

The recent claim of potential room-temperature superconductivity in Pb $_{10 - x}$ Cu $_{x}$ (PO $_{4}$ ) $_{6}$ O has attracted widespread attention. However, the signature of superconductivity is later attributed to the Cu $_{2}$ S impurity formed during the multiple-step synthesis procedure. Here we report a simple one-step approach to synthesize single-phase chloride analogue Cu-doped Pb $_{10}$ (PO $_{4}$ ) $_{6}$ Cl $_{2}$ using PbO, PbCl $_{2}$ , CuCl $_{2}$ , and NH $_{4}$ H $_{2}$ PO $_{4}$ as starting materials. Irrespective of the initial stoichiometry, the Cu doping always leads to a lattice expansion in Pb $_{10}$ (PO $_{4}$ ) $_{6}$ Cl $_{2}$ . This indicates that Cu prefers to reside in the hexagonal channels rather than substitutes at the Pb site, and the chemical formula is expressed as Pb $_{10}$ (PO $_{4}$ ) $_{6}$ Cu $_{x}$ Cl $_{2}$ . All the Pb $_{10}$ (PO $_{4}$ ) $_{6}$ Cu $_{x}$ Cl $_{2}$ (0 $\leq$ $x$ $\leq$ 1.0) samples are found to be semiconductors with wide band gaps of 4.46-4.59 eV, and the Cu-doped ones ( $x$ = 0.5 and 1.0) exhibit a paramagnetic behavior without any phase transition between 400 and 1.8 K. Our study calls for a reinvestigation of the Cu location in Pb $_{10 - x}$ Cu $_{x}$ (PO $_{4}$ ) $_{6}$ O, and supports the absence of superconductivity in this oxyapatite.

8 pages, 6 figures

One-step synthesis of Cu-doped Pb10​(PO4​)6​Cl2​ apatite: A wide-gap semiconductor

Abstract

One-step synthesis of Cu-doped Pb $_{10}$ (PO $_{4}$ ) $_{6}$ Cl $_{2}$ apatite: A wide-gap semiconductor