Structure and Optical Properties of the Arsenide Oxides REZnAsO (RE = Y, La–Nd, Sm, Gd–Er)

Abstract

Abstract The equiatomic rare earth metal zinc arsenide oxides RE ZnAsO ( RE = Y, La–Nd, Sm, Gd–Er) were synthesized in well crystallized form from the elements, arsenic, and ZnO in NaCl/KCl fluxes in sealed silica ampoules. The samples were characterized by powder and single‐crystal X‐ray data. HoZnAsO and ErZnAsO are reported for the first time. Four structures (ZrCuSiAs type, space group P 4/ nmm ) were refined from single‐crystal X‐ray diffractometer data: a = 394.23(3), c = 884.0(1) pm, wR 2 = 0.0345, 216 F 2 values for YZnAsO, a = 409.56(3), c = 907.0(1) pm, wR 2 = 0.0502, 285 F 2 values for LaZnAsO, a = 397.62(4), c = 889.2(2) pm, wR 2 = 0.0700, 216 F 2 values for GdZnAsO, and a = 392.72(3), c = 881.5(1) pm, wR 2 = 0.0580, 373 F 2 values for ErZnAsO with 12 variables per refinement. The RE ZnAsO structures consist of alternate stacks of ( RE 3+ O 2– ) and (Zn 2+ As 3– ) layers with covalent RE –O (224 pm in ErZnAsO) and Zn–As (255 pm in ErZnAsO) intralayer and weak ionic interlayer bonding. Both layers consist of condensed edge‐sharing OEr 4/4 and ZnAs 4/4 tetrahedra. In agreement with an electron precise formulation RE 3+ Zn 2+ As 3– O 2– , the crystals are transparent with yellow (LaZnAsO) to red color tones. In agreement with the different colors, LaZnAsO shows a significantly higher optical bandgap of E g ≈ 2.3 eV than arsenide oxides RE ZnAsO ( RE = Y, Pr, Nd, Sm) ( E g ≈ 1.9 eV).