All Roads Lead to TiO₂: TiO₂-Rich Surfaces of Barium and Strontium Titanate Prepared by Hydrothermal Synthesis

Abstract

Through high-resolution electron microscopy, the surface structure of barium titanate and strontium titanate nanoparticles are found to be terminated by a TiO 2 double layer. These results confirm prior observations of TiO 2 -rich surface reconstructions on strontium titanate nanoparticles made hydrothermally at high pH and single crystals prepared with wet chemical etching. Of all the reconstructions observed on single crystals for these two materials, we report for first time the √13 × √13R33.7°structure on the {001} facets of hydrothermally prepared barium titanate and strontium titanate nanocrystals. The aqueous environment common to the two preparation methods preferentially leaves strontium and barium depleted from the A-sites near the surface and leads to TiO 2 -terminated surfaces for both materials. Analysis indicates that the observed structures are the thermodynamic lowest energy structures in aqueous conditions.

Upcycling Single-Use Polyethylene into High-Quality Liquid Products

“…26,27 The SrTiO 3 used in the present study features single crystal nanocuboids having a sub-100 nm average size, with {100} facets and rounded stepped edges. It is synthesized under hydrothermal conditions, 28,29 and the majority {100} surface termination has been determined to be the (√13 × √13)R33.7° TiO 2 double-layer surface reconstruction. 25,28−33 The SrTiO 3 nanocuboids are used as a support for deposition of Pt NPs to form a Pt/SrTiO 3 hydrogenolysis catalyst.…”

“…It is synthesized under hydrothermal conditions, 28,29 and the majority {100} surface termination has been determined to be the (√13 × √13)R33.7° TiO 2 double-layer surface reconstruction. 25,28−33 The SrTiO 3 nanocuboids are used as a support for deposition of Pt NPs to form a Pt/SrTiO 3 hydrogenolysis catalyst. Atomic layer deposition (ALD) is chosen for this process because it allows programmed control over key catalyst features that are potentially important to hydrogenolysis.…”

Polyethylene Glycol as Shape and Size Controller for the Hydrothermal Synthesis of SrTiO3 Cubes and Polyhedra

“…The synthesis of strontium titanate can be carried out following several methods [ 15 , 16 , 17 , 18 , 19 ]. Among these, hydrothermal synthesis allows the preparation of exceptionally pure crystals with high specific surface area, as well as control of morphology through the variation of synthesis parameters like precursors, temperature, time, pH, shape controllers, etc.…”

“…Among these, hydrothermal synthesis allows the preparation of exceptionally pure crystals with high specific surface area, as well as control of morphology through the variation of synthesis parameters like precursors, temperature, time, pH, shape controllers, etc. [ 16 , 20 , 21 , 22 ]. The synthesis of shape and size-controlled crystals, in particular at nanometer and sub-micrometer level, is crucial to understanding the dependence of the functional properties on the morphological characteristics of the particulate material at nanoscale [ 6 , 23 ].…”

Subsurface reconstruction and saturation of surface bonds

“…In addition, the correction of the spherical aberration has eliminated most contrast delocalization in high-resolution images [31,32]. In the profile imaging mode [33], aberration-corrected TEM has been shown to be a powerful tool for studies of oxide surfaces at a truly atomic scale [17,[34][35][36][37][38] .…”