Unveiling the brittleness of hybrid organic–inorganic 0-D histammonium zinc chlorometallate by nanoindentation

Abstract

Hybrid organic–inorganic halometallates, with different organic and inorganic components, can provide a wide array of tunable physical properties. While many optoelectronic phenomena are being explored, research on the mechanical properties of this class of materials, especially fracture toughness, is lacking, resulting in conclusions on material flexibility being drawn from their elastic modulus and hardness alone with an implicit assumption that these properties correlate with material flexibility. In this Letter, we report nanoindentation results on the elastic modulus, hardness, and fracture toughness of single crystal samples of hybrid organic–inorganic histammonium chlorozincate, HistZnCl4 along the [001] axis. We find that the elastic modulus is 12.078 ± 1.034 GPa, and the hardness is 0.611 ± 0.089 GPa. Moreover, the fracture toughness of this sample is measured to be 0.098 MPa m12. Although these materials have a hardness to modulus ratio similar to that of metals, they fracture like brittle materials, demonstrating the importance of conducting studies on a material fracture toughness before determining their applicability in flexible device applications.

Structure and Piezoelectricity Due to B Site Cation Variation in ABn+Cln+2Hybrid Histammonium Chlorometallate Materials

“…Both colorless HistNH 3 ZnCl 4 and deep blue HistNH 3 CoCl 4 materials are isostructural (Figure a,b) and were both found to crystallize from an equimolar mixture of MCl 2 (M = Co, Zn) and histammonium dihydrochloride in a non-centrosymmetric space group ( Pna 2 1 ) in a stacked network of a 0-D structure. We had previously grown crystals of HistNH 3 ZnCl 4 and studied its mechanochemical properties by nanoindentation measurements, and during the course of the current work, we discovered that others had reported the crystal structures of HistNH 3 ZnCl 4 and HistNH 3 CoCl 4 before. , …”

“…For each of the materials, it was difficult to consistently see a response displacement from the sample at the applied voltages. We attribute this to difficulties we had in sample mounting, as the crystals were highly brittle and damaged easily, 17 which led to poor electrical contact in some cases. Only the Zn-containing material grew large enough crystals in our hands to measure on a specific face (a−c face).…”