[NH2(C2H4)2O]MX5: a new family of morpholinium nonlinear optical materials among halogenoantimonate(iii) and halogenobismuthate(iii) compounds. Structural characterization, dielectric and piezoelectric properties

Abstract

This paper presents the structural features of ionic complexes formed by morpholine and metal ions which belong to group VA, namely Sb(III) and Bi(III). A series of target inorganic–organic hybrid compounds of the general formula [NH₂(C₂H₄)₂O]₂MX₅ (where M = Sb, Bi; X = Cl, Br) has been synthesized by incorporating the organic component (morpholine) into the highly polarizable one-dimensional halogenoantimonate(III)/halogenobismuthate(III) chain network. Among the studied compounds, four were found to crystallize in the room temperature phase in the piezoelectric, orthorhombic space group P2₁2₁2₁, Z = 4, the feature being confirmed by the powder second harmonic generation of light and piezoelectric measurements. Dielectric dispersion studies between 200 Hz and 2 MHz disclosed a relaxation process below room temperature well described by the Cole–Cole equation. Based on crystal structures available in Cambridge Structural Database (version 5.32, November 2010) we attempt to show a relationship between the acentric symmetry of compounds and the type of anionic network within the R₂MX₅-subgroup (where R denotes organic cation) of halogenoantimonates(III) and halogenobismuthates(III).