Probing disorder in high-pressure cubic tin (IV) oxide: a combined X-ray diffraction and absorption study

Abstract

The transparent conducting oxide, SnO2, is a promising optoelectronic material with predicted tailorable properties via pressure‐mediated band gap opening. While such electronic properties are typically modeled assuming perfect crystallinity, disordering of the O sublattice under pressure is qualitatively known. Here a quantitative approach is thus employed, combining extended X‐ray absorption fine‐structure (EXAFS) spectroscopy with X‐ray diffraction, to probe the extent of Sn—O bond anharmonicities in the high‐pressure cubic () SnO2 – formed as a single phase and annealed by CO2 laser heating to 2648 ± 41 K at 44.5 GPa. This combinational study reveals and quantifies a large degree of disordering in the O sublattice, while the Sn lattice remains ordered. Moreover, this study describes implementation of direct laser heating of non‐metallic samples by CO2 laser alongside EXAFS, and the high quality of data which may be achieved at high pressures in a diamond anvil cell when appropriate thermal annealing is applied.

Extreme structural stability of Ti0.5Sn0.5O2 nanoparticles: synergistic effect in the cationic sublattice

“…32 This effect has recently been confirmed by a combination of XRD and EXAFS. 47 The effect of decoupling between the two sublattices has been observed in pressure-induced phase transitions in complex structures of rare earth molybdates (RE(MoO 4 ) 3 with RE = Gd, Eu, Tb, Nd), for which two-step amorphization has been reported regardless of the form of the samples. The anionic sublattice begins to exhibit amorphous-like Raman, photoluminescence, or EXAFS signatures at a pressure lower than that of the cationic sublattice probed by X-ray diffraction.…”

Very Small Nanocrystalline Tin Dioxide Particles: Local-, Crystal-, and Micro-Structure

“…Applying high pressures above 7 GPa to 3 nm nanocrystals introduces disorder on the oxygen sublattice as observed by Raman spectroscopy but not by X-ray powder diffraction due to the different element sensitivities of both methods . Sneed et al investigates cubic SnO 2 at 44.5 GPa by XRD and EXAFS and find good agreement between Rietveld refinement and EXAFS data analysis regarding the Sn–Sn distances but significant differences for the Sn–O coordination due to disorder in the oxygen sublattice. Jensen et al uses in situ total scattering to investigate the mechanisms of SnO 2 nanoparticle formation and growth.…”

Anomalous Conductivity in the Rutile Structure Driven by Local Disorder

“…11,12 Meanwhile, in the high-pressure cubic SnO 2 , extended X-ray absorption fine structure spectroscopy (EXAFS) measurements have allowed the direct measurements of O sublattice disorder. 13 As a transparent conducting oxide, SnO 2 has far-reaching technological applications 14 and has been predicted to exhibit pressure-mediated opening of its electronic band gap 15 from its ambient value of 3.6 eV 16,17 as is the case for its Sn(IV) nitride counterpart. 18 Given the intrinsic link between electronic properties of a material and its crystalline structure, such disordering necessitates further, quantitative study.…”

“…EXAFS data is modeled here using the cumulant expansion of the EXAFS equation following Fornasini et al 26 for its precedent in describing structural anharmonicities and disorder, 27 provided an absence of anisotropic strain is ensured either by thermal annealing 13 or here by the use of a fluid He PTM. Upon fitting the data to the cumulant-expanded EXAFS equation (details of fitting are in the Supporting Information), the average Sn−O distance in the first coordination octahedron, as well as the mean squared relative displacements (MSRD) of the O, can be extracted.…”

“…Recently, the tendency of SnO 2 to undergo anion sublattice disordering under pressure has been studied across a variety of sample morphologies with Raman spectroscopy as a probe for the partial amorphization of the O sublattice of the material, while its Sn sublattice remains ordered. , Meanwhile, in the high-pressure cubic SnO 2 , extended X-ray absorption fine structure spectroscopy (EXAFS) measurements have allowed the direct measurements of O sublattice disorder . As a transparent conducting oxide, SnO 2 has far-reaching technological applications and has been predicted to exhibit pressure-mediated opening of its electronic band gap from its ambient value of 3.6 eV , as is the case for its Sn­(IV) nitride counterpart .…”