Crystal structure of chalcogenides R'xR''yR'''zPbSi2S8 (R' – La, R'' – Tb, R''' – Er)

O.V Marchuk,Yu Prots,O.V Smitiukh,A.O Fedorchuk

doi:10.15330/pcss.22.4.621-629

Abstract

The chalcogenides LaxTbyErzPbSi2S8 were obtained by synthesizing the elementary components in vacuum quartz containers at 1320 K. The synthesized alloys were homogenized by annealing at 770 K during 500 hours. The cell parameters of synthesized sulfides are: a = 0,89576(3) nm, c = 2,65646(8) nm – La1,2Tb0,4Er0,4PbSi2S8; a = 0,89209(1) nm, c = 2,63466(5) nm – La0,9Tb0,2Er0,9PbSi2S8; a = 0,89002(3) nm, c = 2,62714(7) nm – La0,67Tb0,67Er0,67PbSi2S8; a = 0,88993(1) nm, c = 2,62973(4) nm – La0,6Tb1,2Er0,2PbSi2S8; a = 0,885161(7) nm, c = 2,60445(3) nm – La0,2Tb0,9Er0,9PbSi2S8 respectively. The atoms of statistical mixture (La,Tb,Er,Pb) occupy the site 18e (x y 1/4), and the atoms of Si occupy the site 12c (1/3 2/3 z) in the structure of the obtained chalcogenides. Coordinating polyhedra of atoms of the statistical mixture (La, Tb, Er, Pb) are trigonal prism with two additional atoms (CN = 8), and the atoms of Si occupying the crystallographic point system 12c describes with the tetrahedron. According to the results of the experiment, the synthesized chalcogenides crystallize in the structure type of La2PbSi2S8 (hR26,167). The structure of La2PbSi2S8 is described by using the theory of second anion coordination (SAC).

Highlights

Search for new crystalline solids with tunable physical properties originating from the synergistic effect of the unique crystal structure and bonding nature is among the main streams in modern material science [1-3]
According to the prospects of chalcogenide phases, which crystal structure consists of rare earth metals (REM) atoms, we can reasonably confirm that the synthesis of multi-component chalcogenides and detailed investigation of the relationship between their crystal structure and properties can be effectively utilized for designing new advanced functional materials
We present results of investigations of crystal structures of chalcogenides La1.2Tb0.4Er0.4PbSi2S8, La0.9Tb0.2Er0.9PbSi2S8, La0.67Tb0.67Er0.67PbSi2S8, La0.6Tb1.2Er0.2PbSi2S8 and La0.2Tb0.9Er0.9PbSi2S8, which are distinct compositions of the quasi-ternary

Summary

Introduction

Search for new crystalline solids with tunable physical properties originating from the synergistic effect of the unique crystal structure and bonding nature is among the main streams in modern material science [1-3]. The properties and crystal structure of multi-component chalcogenides and rare earth metals (REM) containing chalcogenides [4-6], are investigated systematically regarding their practical utilization [7-12]. Adding REM atoms with different chemical nature in terms of 4f electronic level occupancy into the crystal structure of chalcogenides, is a good way to develop semiconductors with desired properties, as such examples are CaY2Si2S8:Ce3+ [13], BaLa2Si2S8:Eu2+ [14], (Gd,Ce)4(SiS4), (Y,Ce)4(SiS4)3 [15], (La,Ce,Y)6Si4S17 [16], LaR'PbSi2S8, CeR'PbSi2S8, PrR'PbSi2S8 (R' = Ce, Pr, Sm, Tb, Dy, Y, Ho and Er) [17] and others. According to the prospects of chalcogenide phases, which crystal structure consists of REM atoms, we can reasonably confirm that the synthesis of multi-component chalcogenides and detailed investigation of the relationship between their crystal structure and properties can be effectively utilized for designing new advanced functional materials. La2PbSi2S8 – Tb2PbSi2S8 – Er2PbSi2S8 system, by using of powder X-ray diffraction method

Experimental section

Results

Discussion of results

Conclusions