Facile and General Synthesis of Thermally Stable Ordered Mesoporous Rare-Earth Oxide Ceramic Thin Films with Uniform Mid-Size to Large-Size Pores and Strong Crystalline Texture

Abstract

We describe the general synthesis of sub-micron-thick rare-earth/lanthanide sesquioxide (RE 2 O 3 ) films with tailorable pore and grain sizes by polymer templating of hydrated chloride salt precursors. Mesostructured RE 2 O 3 (RE = Sm, Tb-Lu) ceramics with cubic pore symmetry and high surface area (S BET ≥ 50 m 2 •g -1 ) were prepared using different diblock copolymer structure-directing agents and were characterized by a combination of electron microscopy, in situ and ex situ grazing incidence small-angle X-ray scattering, N 2 -physisorption, X-ray photoelectron spectroscopy, X-ray diffraction including Rietveld refinement, and UV-vis spectroscopy. In the present work, we specifically focus on Dy 2 O 3 and Yb 2 O 3 and use both of these materials as model systems to study, among other things, the film formation and microstructure. Our research data collectively demonstrate that (1) record pore sizes of up to 42 nm in diameter can be achieved without the need for swelling agents, (2) the nanostructure can be preserved up to 1000 °C for the heavier oxides, (3) the sizes of the optical band gaps (4.9-5.6 eV) are comparable to those reported for single crystals, (4) the sol-gel derived materials are single phase and adopt the C-type crystal structure, and that (5) and Lu 2 O 3 films (March G 2 parameters of under 0.1). Overall, the synthesis parameters described in this work provide a blueprint for the preparation of thermally stable rare-earth oxide ceramics with both a mesoporous morphology and iso-oriented nanocrystalline walls.

Large-Pore Mesoporous Ho3Fe5O12 Thin Films with a Strong Room-Temperature Perpendicular Magnetic Anisotropy by Sol–Gel Processing

“…As already indicated by AFM and TEM, the degree of pore ordering is not very high and is certainly less pronounced than in other polymer-templated nonsilicate oxides. [31][32][33][34][35][39][40][41][42][43][44] However, considering that the garnet material studied in this work is much more complex than the many binary oxides reported in the literature over the past two decades, the overall structure seems rather well-developed. The GISAXS patterns further indicate significant lattice contraction in the direction perpendicular to the substrate plane as a result of the progressive densification of the inorganic matrix and the associated release of NO x and H 2 O (see TGA-MS data in Figure S3 in the SI) upon heating; the in-plane contraction is negligible.…”

Ordered Mesoporous Thin Film Ferroelectrics of Biaxially Textured Lead Zirconate Titanate (PZT) by Chemical Solution Deposition

“…[47][48][49] Both of these structures are common in KLE-templated inorganics. [50][51][52] The degree of order is not as high as in other polymer-templated non-silicate thin films 32,34,42,53,54 -the vast majority are binary transition metal oxides -but the material studied in this work is rather complex from a chemical point of view in that three different sol-gel precursors were used in the synthesis. Furthermore, it can be seen that the material undergoes large unidirectional lattice contraction, namely, perpendicular to the substrate plane.…”

Easy and General Synthesis of Large‐Sized Mesoporous Rare‐Earth Oxide Thin Films by ′Micelle Assembly′

“…Sesquioxide (RE 2 O 3 ) is the most stable oxide in ambient atmosphere compared with monoxide (REO) and dioxide (REO 2 ) . Due to the attracting properties of RE 2 O 3 , such as luminescence, giant magnetoresistance, and partially filled 4f orbitals, there is a high need for a simple synthesis of RE 2 O 3 . There are many potential uses of rare‐earth metal oxides: as catalyst, dielectric gate, and optical device .…”