Synthesis and characterization of K and Eu binary phosphides

Abstract

The synthesis, structural characterization, and optical properties of the binary Zintl phases of α-EuP 3 , β-EuP 3 , EuP 2 , and α-K 4 P 6 are reported in this study. These crystal structures demonstrate the versatility of P fragments with dimensionality varying from 0D (P 6 rings in α-K 4 P 6 ) to 1D chains (EuP 2 ) to 2D layers (both EuP 3 ). EuP 2 is isostructural to previously reported SrP 2 and BaP 2 compounds. The thermal stabilities of the EuP 2 and both EuP 3 phases were determined using differential scanning calorimetry (DSC), with melting temperatures of 1086 K for the diphosphide and 1143 K for the triphosphides. Diffuse reflectance spectroscopy indicated that EuP 2 is an indirect semiconductor with a direct bandgap of 1.12(5) eV and a smaller indirect one, less than 1 eV. Both EuP 3 compounds had bandgaps smaller than 1 eV.