title: Synthesis, Crystal Structure, and Properties of La4Zn7P10and La4Mg1.5Zn8.5P12.
abstract: Two new zinc phosphides, La4Zn7P10and La4Mg1.5Zn8.5P12, were synthesized via transport reactions, and their crystal structures were determined by single crystal X-ray diffraction. La4Zn7P10and La4Mg1.5Zn8.5P12are built from three-dimensional Zn-P and Zn-Mg-P anionic frameworks that encapsulate lanthanum atoms. The anionic framework of La4Zn7P10is constructed from one-dimensional Zn4P6, Zn2P4, and ZnP4chains. The Zn4P6chains are also the main building units in La4Mg1.5Zn8.5P12. In La4Zn7P10, the displacement of a zinc atom from the origin of the unit cell causes the Zn4 position to split into two equivalent atomic sites, each with 50% occupancy. The splitting of the atomic position substantially modifies the electronic properties, as suggested by theoretical calculations. The necessity of splitting can be overcome by replacement of zinc with magnesium in La4Mg1.5Zn8.5P12. Investigation of the transport properties of a densified polycrystalline sample of La4Zn7P10demonstrates that it is an n-type semiconductor with a small bandgap of ∼0.04 eV at 300 K. La4Zn7P10also exhibits low thermal conductivity, 1.3 Wm-1K-1at 300 K, which mainly originates from the lattice thermal conductivity. La4Zn7P10is stable in a sealed evacuated ampule up to 1123 K as revealed by differential scanning calorimetry.
authors.affiliation: Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States.
authors.forename: Kathleen
authors.identifier: http://orcid.org/0000-0002-1476-5384
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Chemistry, University of California, Davis , One Shields Avenue, Davis, California 95616, United States.
authors.forename: Kirill
authors.identifier: http://orcid.org/0000-0003-1152-1912
authors.initials: K
authors.lastname: Kovnir