Synthesis, structure and electronic properties of the cerium and potassium thiosilicate: KCeSiS4

Abstract

Abstract The cerium and potassium thiosilicate KCeSiS 4 has been synthesized at 800 °C from Ce, Si, K 2 S and S precursors weighted in the K:Ce:Si:S = 1:1:1.15:4.3 ratio. This yellow, air stable compound crystallizes in the monoclinic space group P2 1 , (No. 4) with the cell parameters: a = 6.5201(3) A, b = 6.5982(3) A, c = 8.6920(5) A, β = 107.701(3) °, V = 356.23(3) A 3 and Z = 2. Refinement of 36 parameters by the Rietveld method, using 974 reflections led to R p (%) = 2.49, R wp (%) = 3.35 and χ 2 = 2.71. KCeSiS 4 , isostructural to KLnMQ 4 (Ln = La, Nd, Gd, Y; M = Si, Ge; Q= S, Se), consists of two-dimensional ∞ 2 [CeSiS 4 ] − anionic layers separated by K + ions. These layers are built upon [CeS 7 ] distorted monocapped trigonal prisms, sharing 2 edges and 2 corners with each other, and upon [SiS 4 ] tetrahedra linked to the ∞ 2 [CeS 4 ] 5− skeleton by edge and face sharing. From magnetic measurements, an effective magnetic moment μ eff (300 K) = 2.73(2) μ B was calculated in good agreement with the k (i) Ce (III) Si (IV) S 4 (−II) charge balance. From diffuse reflectance measurements, a band gap of 2.68(1) eV correlated to the occurrence of a 4 f → 5 d electronic transition was evidenced. Moreover, chromatic L/a/b coefficients, equal respectively to 88.37/−18.85/52.91, have been determined for the bright yellow colour of the compound. These parameters compare rather well with those of NiTiO 3 , a well known industrial pigment. The room temperature strong green luminescence at E = 2.45 eV( λ = 506.1 nm) of KCeSiS 4 has been investigated through emission and excitation spectroscopy in the UV-visible range.