Ce Precursor Research Articles

Initial Research on the 1%CuO – 6CeO2 – 4ZrO2 Catalysts by TPR-H2 for the Carbon Monoxide Preferential Oxidation (CO-PROX Reaction)

The 1wt%CuO – 6CeO2 – 4ZrO2 catalysts were synthesized by sol-gel method with two different procedures: (i) impregnating CuO on CeO2-ZrO2 support (CuO/CeO2-ZrO2), (ii) sol-gel of the Cu, Ce and Zr precursor together (CuO-CeO2-ZrO2). These catalysts were applied for the preferential oxidation of carbon monoxide (CO-PROX) to remove a small quantity of CO in an H2-rich stream (the new research direction in Viet Nam), fueling the proton exchange membrane fuel cell (PEMFC) energy system. The findings of the TPR-H2 experiment indicated that the catalyst produced through the first method exhibited an α reduction peak at 174 °C, which shows the effective dispersion of copper species. In combination with EPR results, the author anticipates a significant dispersion arising from isolated copper, which is recognized as a pivotal site in the CO-PROX reaction per numerous reputable studies. The catalyst synthesized by the second method did not provide a clear indication of the oxidation behavior of Cu-species. Therefore, it can be inferred that this catalyst is inappropriate for the low-temperature CO-PROX reaction.

Influence of Precipitation Conditions on Properties of Ceria and their Implications on the Mars‐van‐Krevelen Active Surface Area

AbstractQuantifying the active surface area of Mars‐van‐Krevelen catalysts is paramount for the elucidation of structure‐property relationships and the knowledge‐based catalyst development. Different cerium oxides were prepared via precipitation‐based techniques. By altering conditions during precipitation, materials with a wide span of material properties were prepared. The influence of temperature during ammonia‐based precipitation was investigated. When using Ce(IV) precursors an increase in precipitation temperature decreases the crystallite size while increasing specific surface area, attributed to an increase in nucleation rate. Sintering stability is also increased for materials precipitated at higher temperature. Measuring the total oxygen storage capacity (TOSC) values of the prepared materials showed that the TOSC is not strictly a function of BET surface area. Our results suggest that crystallites with a domain size under a certain threshold are not reduced via oxygen release but rather hydroxyl formation. A method was proposed with which the redox active surface area for polycrystalline ceria can be estimated on basis of the domain size obtained from Rietveld refinement. These findings were corroborated by CO oxidation light‐off experiments in which the light‐off temperature was found to correlate with the surface that can release oxygen reversibly, the Mars‐van‐Krevelen active surface area, rather than BET surface area.

Reduced graphene oxide-supported palladium oxide-MOx for improving the performance of air-cathode microbial fuel cells: Influence of the Sn, Ce, Zn, and Fe precursors

Over the past few decades, microbial fuel cells (MFCs) have attracted significant interest within the realm of renewable energy technologies owing to their capability to generate electricity from low-grade substrates. However, their commercialization and scaling-up are impeded by significant obstacles, including high capital costs, limited durability, and sluggish oxygen reduction reaction (ORR). Here, we demonstrate an environmentally-friendly approach for developing highly efficient electrocatalysts consisting of palladium oxide (PdO) and different transition metal oxides (i.e., tin (IV) oxide (SnO2), ceric oxide (CeO2), iron (III) oxide (Fe2O3), and zinc oxide (ZnO)) embedded within reduced graphene oxide (rGO) framework for improving the efficiency of ORR in neutral medium and MFCs. Among the as-prepared electrocatalysts, the PdO–SnO2/rGO possesses the highest ORR electrochemical catalytic activity in a neutral medium (pH ∼ 7.2) following a four-electron ORR pathway, with a current density slightly lower than that of benchmark Pt/C electrocatalyst. The assessment of MFC performance is conducted by employing activated sludge as the inoculum and glucose as the sole electron donor in the anode chamber of single-chamber, air-cathode MFCs. Consistent with electrochemical performance, the maximum power output of an MFC equipped with PdO–SnO2/rGO as an air cathode is significantly higher than other tested MFCs, reaching 84.6 ± 2.8 mW m−2, which represents ∼ 91 % of the power output of an MFC with Pt/C air cathode. Our results reveal that the incorporation of PdO into transition metal reduced graphene oxide framework has the potential to facilitate their long-term application as air cathodes in MFCs that possess easy fabrication, relatively affordable cost, and outstanding electrochemical catalytic oxygen reduction capability, for enhancing electricity generation from wastewater.

Intensified synthetic approach for GdYAG:Ce phosphors with ultrahigh color rendering toward healthy lighting

AbstractProcess intensified synthetic approach for synthesizing gadolinium and cerium co‐doped yttrium aluminum garnet (GdYAG:Ce) phosphors in white light‐emitting diodes (wLED) is developed. By using a high‐gravity rotating packed bed (RPB) reactor for preparation of sol–gel precursors, the significantly enhanced molecular mixing allows precise control and tuning of dry gel with designed structure to obtain nanosized particles of GdYAG:Ce precursors, which are prone to low temperature quick sintering process and therefore reduce the energy consumption of the electric furnace 76% compared to solid phase method. By analyzing the effect of cycling times and high gravity levels of RPB reactor on sintering and crystallization, sintering condition for emission spectrum adjustable GdYAG:Ce phosphors is optimized. Prototype devices based on blue chips and GdYAG:Ce phosphors exhibit high color rendering index of 83.8 and low correlation color temperature of 5357 K that are beneficial for creating a healthy and comfortable lighting environment.

Effect of precipitation variables on the performance of CeO2-based catalysts for waste-to-hydrogen

Waste-to-hydrogen technology, a future net-zero energy mix as a clean hydrogen source, is currently a research hotspot. To upcycle waste to high-value chemicals such as hydrogen, it is necessary to study customized catalysts for water-gas shift (WGS) reactions considering waste-derived synthesis gas. Herein, we aimed to enhance the physicochemical properties of CeO2 supported Pt catalysts by controlling the precipitation variables to develop a highly sulfur-tolerant WGS catalyst using waste-derived synthesis gas. The CeO2 support was prepared by the classic precipitation method. During precipitation, the precipitating agent was injected at different methods and rates. In the case of the normal titration method, the KOH solution was injected into the Ce precursor dissolved solution at rates of 5, 20, and 50 mL/min. In the case of the reverse titration method, the Ce precursor dissolved solution was injected into the KOH solution at rates of 5, 20, and 50 mL/min. The as-prepared Pt/CeO2 catalysts were applied to the WGS reaction with 500 ppm H2S. This work demonstrated that the titration method and titration rate affected the oxygen vacancy concentration and the active metal dispersion of the catalysts, respectively. And these properties worked in combination to determine the sulfur resistance of the catalysts. Subsequently, the high sulfur tolerance and catalytic performance of Pt/CeO2 catalyst prepared by normal titration method with the titration rate of 50 mL/min were due to the high Pt dispersion and concentration of oxygen vacancies.

Ce & F multifunctional modification improves the electrochemical performance of LiCoO2 at 4.60 V

Lithium cobalt oxide (LiCoO2) is proverbially employed as cathode materials of lithium-ion batteries attributed to the high theoretical capacity, and currently, it is developing towards higher cut-off voltages in the pursuit of higher energy density. However, it suffers from serious structural degradation and surface side reactions, in particular, at the voltage above 4.60 V, leading to rapid decay of the battery life. Taking into account the desirable oxygen buffering property and the fast ion mobility characteristic of cerium oxide fluoride, in this work, we prepared Ce & F co-modified LiCoO2 by using the precursors of Ce(NO3)3·6H2O and NH4F, and evaluated the electrochemical performance under voltages exceeding 4.60 V. The results indicated that the modified samples have multiphase heterostructure of surface CeO2−x and unique CeOF solid solution phase. At 3.0–4.60 V and 25 °C, the preferred sample LCO-0.5Ce-0.3F has a high initial discharge specific capacity of 221.9 mA h g−1 at 0.1 C, with the retention of 80.3% and 89.6% after 300 cycles at 1 and 5 C, comparing with the pristine LCO (56.4% and 22.6%). And at 3.0–4.65 V, its retention is 64.0% after 300 cycles at 1 C, versus 8.5% of the pristine LCO. Through structural characterizations and DFT calculations, it suggests that Ce4+ & F− co-doping suppresses the H3 to H1/3 irreversible phase transition, stabilizes the lattice structure, and reduces the redox activity of the lattice oxygen by modulating the Co 3d–O 2p energy band, consequently improving the electrochemical performance of LiCoO2 at high voltages.

From Ce(OH)3 to Nanoscaled CeO2: Identification and Crystal Structure of a Cerium Oxyhydroxide Intermediate Phase

Cerium oxide is a pivotal compound in catalysis, both as a support and as an active phase. However, its fine features, such as the Ce(III) to Ce(IV) ratio, strongly depend on the protocol used to prepare it. While the literature contains tens of protocols to prepare cerium oxide nanoparticles from Ce(III) precursors, there is still an open question regarding the time at which the cerium oxidation occurs and the role of hydroxide phases in this process. This article identifies an oxyhydroxide phase of Ce(IV) as a key intermediate and proposes a crystal structure for it. For this purpose, phase-pure cerium trihydroxide (Ce(OH)3) nanorods (<20 nm) were first prepared by hydrothermal treatment of a cerium nitrate salt (Ce(NO3)3·6H2O) in the presence of KOH. Aging of this phase in air was monitored by X-ray absorption spectroscopy, which confirmed the formation of an intermediate Ce(IV) crystalline compound, unreferenced so far. Based on X-ray and neutron powder diffraction experiments combined with DFT calculations, we propose that this new phase is a cerium oxyhydroxide of the chemical formula CeO(OH)2, for which a structural model is proposed. Thermodiffraction experiments finally established that this compound is an observable intermediate in the synthesis of cerium dioxide CeO2 by calcination of Ce(OH)3 in air.

Palladium and cerium oxide hollow strings of pearls for stable and wide-concentration-range hydrogen sensing at room temperature

Hydrogen (H2) sensing materials of palladium (Pd) adsorb H2 and form PdHx, however, the H2 adsorption saturation limits its detection range and stability. Here, Pd and cerium oxide hollow strings of pearls (Pd/CeO2 HSPs) have been synthesized for stable and wide-concentration-range H2 sensing via cross-linked carbon nanospheres template adsorbing Pd and Ce precursors, followed by annealing and reducing. Specifically, Pd/CeO2 HSPs are observed with HSP geometrical shapes, in which numerous holes are distributed over their surface. Beneficially, the Pd/CeO2 HSPs exhibit outstanding sensing response to 0.01–30 v/v% H2, and show high repeatability and stability upon repeated exposure to 1 v/v% H2 at room temperature (∼25 °C). The excellent sensing performance may be attributed to the synthetic effect that hollow and porous structure provides sufficiently permeable pathways and adsorption sites for H2 molecules, the SPs facilitate the transfer of electrons and CeO2 render Pd/CeO2 HSPs with high structural-stability by avoiding agglomeration of Pd particles. Practically, Pd/CeO2 HSPs sensor prototype has been simulated to detect H2 leakage with reliable H2 sensing.

Effect of Ce-BTC precursor morphology on CuO/CeO2 catalysts for CO preferential oxidation in H2-rich gas

In this paper, the precursors of the coordination polymer Ce(1,3,5-BTC)(H2O)6 with different morphologies have been successfully prepared via a facile and rapid method, and then the CuO/CeO2 catalysts were obtained by impregnation method to support copper species. The catalysts were characterized by scanning electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, ultraviolet Raman spectrscopy, N2 adsorption-desorption, H2 programmed temperature reduction and X-ray photoelectron spectroscopy, respectively. The results showed that U–CuCeO catalyst has stronger CuO dispersion and higher oxygen vacancy concentration on the surface. The high specific surface area of U–CuCeO catalyst facilitates the highly dispersed CuO species and enhances the interaction between copper and cerium, and improves the catalytic performance compared with the other catalysts. For U–CuCeO catalyst, the CO conversion reached 100% at 120 °C. It also exihibited the broadest complete reaction temperature window.

Synthesis and Characterization of Cerium Oxide Nanoparticles: Effect of Cerium Precursor to Gelatin Ratio

Hemocompatible nanoparticles with reactive oxygen species (ROS) scavenging properties for titanium implant surface coatings may eliminate implant failure related to inflammation and bacterial invasion. Cerium (Ce) is a rare earth element, that belongs to the lanthanide group. It exists in two oxidation states, Ce+3 and Ce+4, which contribute to antioxidant, catalytic, antibacterial, and ROS-scavenging properties. The purpose of the present study was to synthesize ceria nanoparticles and to evaluate their hemocompatibility and ROS scavenging properties. The synthesis of Ce-NPs was performed via the sol-gel method, and five different ratios of cerium precursors to gelatin were evaluated. Their characterization was achieved through FTIR, XRD, SEM, and TEM. Hemocompatibility and ROS analysis were evaluated at different concentrations with human erythrocytes. The morphology and size distribution were certified by TEM and the cubic CeO2 fluorite structure was identified by selected area electron diffraction and high-resolution TEM. The particle size of the lowest Ce concentration presented a mean diameter of 10 nm. At concentrations of &lt;500 μg/mL, no hemolytic effect was observed. At the highest concentrations, no hemolytic behavior was recorded for samples with the highest Ce precursor, which also presented ROS scavenging properties (10–50% reduction in ROS). These properties make those CeO2 NPs unique candidates as nanofillers or nanocoatings with antibacterial properties.

Accelerated catalytic ozonation for aqueous nitrobenzene degradation over Ce-loaded silicas: Active sites and pathways

Cerium oxides loaded silica catalysts were synthesized by an impregnation method by simply mixing Ce precursor with silica spherule (Ce/SS) and ordered MCM-41 zeolites (Ce/MCM-41), followed by a mild calcination. Compared with pure SS and MCM-41, Ce modified Ce/SS and Ce/MCM-41 demonstrate much improved catalytic ozonation activities for mineralization of recalcitrant nitrobenzene (NB). At solution pH of 6, 86 and 97% TOC mineralization rates were achieved within 60 min for Ce/MCM-41 and Ce/SS, respectively. Characterization results suggest that Ce loading significantly increases the surface Lewis acidic sites, which would synergize with Ce3+/Ce4+ redox cycle for the activity improvement. With the aid of in situ electron paramagnetic resonance (EPR) spectra and quenching tests, hydroxyl radical (·OH), superoxide radical (O2•–), and singlet oxygen (1O2) are identified as the O3 catalytic decomposition products, while ·OH mainly accounts for NB mineralization. The detailed degradation route of NB was further investigated by the multi-chromatography analysis. NB is firstly oxidized into polyhydroxy compounds, followed by small molecular organic acids, and finally being mineralized into CO2 and H2O. This study established a facile strategy to synthesize highly active and stable Ce/SiO2 catalysts for catalytic ozonation, and elucidated the in-depth mechanisms for the activity origins of the Ce loaded silica-based materials in catalytic ozonation processes (COP).

Low-temperature dry reforming of methane tuned by chemical speciations of active sites on the SiO2 and γ-Al2O3 supported Ni and Ni-Ce catalysts

The cognition of active sites in the Ni-based catalysts plays a vital role and remains a huge challenge in improving catalytic performance of low temperature CO2 dry reforming of methane (LTDRM). In this work, typical catalysts of SiO2 and γ-Al2O3 supported Ni and Ni-Ce were designed and prepared. Importantly, the difference in the chemical speciations of active sites on the Ni-based catalysts is revealed by advanced characterizations and further estimates respective catalytic performance for LTDRM. Results show that larger [Nin0] particles mixed with [Ni-O-Sin]) species on the Ni/SiO2(R) make CH4 excessive decomposition, leading to poor activity and stability. Once the Ce species is doped, however, superior activity (59.0% CH4 and 59.8% CO2 conversions), stability and high H2/CO ratio (0.96) at 600 °C can be achieved on the Ni-Ce/SiO2(R), in comparison with other catalysts and even reported studies. The improved performance can be ascribed to the formation of integral ([Nin0]-[CeIII-□-CeIII]) species on the Ni-Ce/SiO2(R) catalyst, containing highly dispersed [Nin0] particles and rich oxygen vacancies, which can synergistically establish a new stable balance between gasification of carbon species and CO2 dissociation. With respect to Ni-Ce/γ-Al2O3(R), the Ni and Ce precursors are easily captured by extra-framework Aln-OH groups and further form stable isolated ([Nin0]-[Ni-O-Aln]) and [CeIII-O-Aln] species. In such a case, both of them preferentially accelerate CO2 adsorption and dissociation, causing more carbon deposition due to the disproportionation of superfluous CO product. This deep distinguishment of chemical speciations of active sites can guide us to further develop new efficient Ni-based catalysts for LTDRM in the future.

One-Pot Production of Pt–Ni Alloy Nanodendrites on Ceria Nanosheet Supporting Materials with High Electrocatalytic Performance Toward Methanol Oxidation and Oxygen Reduction

To create better fuel cell catalysts, effective approaches to generate hybrid materials comprised of intimately connected metal nanocatalysts and nonstoichiometric metal oxides with finely regulated topologies are very desirable. The production of closely connected metal (PtNi alloy)–metal oxide (CeOx, ceria) hybrid nanostructures is reported here using a simple one-pot synthesis technique. Heating a mixed metal (Pt, Ni, and Ce) precursor solution in oleylamine/oleic acid resulted in well-defined PtNi/ceria hybrids, in which PtNi alloy nanodendrites with multiple branches are evenly spread over small-grained ceria nanosheets. The ceria nanosheets in the hybrids have a large number of oxygen vacancies and a high conductivity due to their small grain size. In comparison to carbon-supported counterparts and a commercial catalyst, the prepared PtNi/ceria hybrids exhibited outstanding electrocatalytic activity and stability for both methanol oxidation and oxygen reduction reactions, which can be attributed to the synergistic effects of the Ni component and ceria on the enhancement of the electrocatalytic function. The current technique will be used to create the best multicomponent catalysts for specific processes.

Ligand Conversion in Nanocrystal Synthesis: The Oxidation of Alkylamines to Fatty Acids by Nitrate.

Ligands are a fundamental part of nanocrystals. They control and direct nanocrystal syntheses and provide colloidal stability. Bound ligands also affect the nanocrystals’ chemical reactivity and electronic structure. Surface chemistry is thus crucial to understand nanocrystal properties and functionality. Here, we investigate the synthesis of metal oxide nanocrystals (CeO2-x, ZnO, and NiO) from metal nitrate precursors, in the presence of oleylamine ligands. Surprisingly, the nanocrystals are capped exclusively with a fatty acid instead of oleylamine. Analysis of the reaction mixtures with nuclear magnetic resonance spectroscopy revealed several reaction byproducts and intermediates that are common to the decomposition of Ce, Zn, Ni, and Zr nitrate precursors. Our evidence supports the oxidation of alkylamine and formation of a carboxylic acid, thus unraveling this counterintuitive surface chemistry.

Hierarchical structured nano-polyhedrons of CeO2@ZIF-8 composite for high performance supercapacitor applications

A well-organized composites based on crustal abundance rare earth metal were developed as the potential electrode for high-performance supercapacitors. The new category of hierarchical nano-polyhedrons of cerium (Ce) doped ZIF-8 composite electrodes were prepared through wet-chemical strategy by varying the concentrations of Ce precursors and determined for their plausible applications in supercapacitors. The XRD and SEM results revealed the structural stability and morphological activity of the prepared composites and then investigated overall energy storage performance. The synthesized composite electrode of Ce-MOF-0.5 using 0.5 mM Ce source with ZIF-8 framework delivered the maximum capacitance of 424.2 F.g−1 by the three-electrode measurement. The optimized Ce-MOF-0.5 electrode incorporated symmetric supercapacitor cell offered an excellent capacitive behavior with the capacitance 132 F.g−1 @ 1 A.g−1, and the device retains the 90% of capacitance upon 5000 cycles during charging-discharging cycles. Further, asymmetric supercapacitor device performance has been assessed and the device delivers high capacitance (89 F.g−1 @ 1 A.g−1), higher energy density (31.3 W.h.kg−1 @ 800 W.kg−1) and indicating higher electrochemical performance of the Ce-MOF-0.5//AC device.

Influence of Ce addition and Pt loading upon the catalytic properties of modified mesoporous PtTi-SBA-15 in total oxidation reactions

A series of PtCeTi-SBA-15 catalysts, with different concentrations of Pt (0.25 %, 0.5 %, 1.0 %), were synthesized. New Ti-SBA-15 material was obtained by direct synthesis and used as support in successive immobilization of Pt and Ce precursors, changing their order of addition. The characterization of the catalysts has been achieved taking an ensemble of techniques which showed preservation of the support porous structure, high dispersion of the amorphous metal oxides and Pt°, the formation of metal crystals for samples with 1wt% Pt and variation of Pt° content on surface in condition of ceria addition. The best conversion (100 %) was obtained in oxidation of hydrocarbons (CH4, C3H8 and C6H14) for the samples with 1% Pt and a significant diminish of activity was obtained for catalyst in which Ce was added on PtTi-SBA-15 sample. Differently of these, CO oxidation was totally irrespective of the catalyst composition.

Ce-Mn oxides synthesized with citric acid on ceramic papers used as diesel particulate filters

Diesel Particulate filters are considered one of the most efficient technologies to reduce particulate matter emitted by diesel engines. In this paper we study the development of catalytic ceramic papers based on Mn-Ce and their applications as soot particle filters in bench scale tests. Ceramic papers were prepared by a dual polyelectrolyte papermaking method and were impregnated with Mn and Ce precursors through a wet-spray procedure using a commercial fogger. Catalytic ceramic papers were tested as catalysts for the combustion of soot, which was obtained both from the burning of diesel fuel and directly from a bench test. In addition, the filtering capacity of catalytic ceramic papers was tested through opacity measurements by placing the ceramic papers in a suitable case at the end of the engine. Mn-Ce based catalysts were active in the soot combustion. The addition of citric acid considerably improved the catalytic performance of all the systems studied. This beneficial effect of citric acid is related to an improvement in the distribution of the catalytic material onto the ceramic fibers, being the mixed equimolar oxide Mn-Ce the most active catalyst.

Tailoring manganese oxide catalysts for the total oxidation of pollutants in gas and liquid phase

Bare and ceria-promoted MnOx catalysts (0 ≤ χMn≤1) were prepared by redox-precipitation reactions of Mn(VII), Mn(II) and Ce(III) or Ce(IV) precursors in slightly acidic (pH, 4.5) or basic (pH, 8.0) environment to assess genesis, nature, and functionality of surface active sites. Both synthesis protocols yield nanostructured materials with large surface area and exposure of Mn sites, featuring high activity in the CO oxidation and the phenol wet-air-oxidation (CWAO) model reactions (T, 423 K). High oxide dispersion prompts an extensive incorporation of Mn(II) ions into ceria substitutional solid-solution structures, forming oxygen-vacancies with stronger oxidation activity than surface Mn(IV) sites. Basic structure-activity relationships indicate that the superior CO oxidation performance of the pristine α-MnO2 system relies on large exposure of very reducible Mn(IV) active sites, while O2-adsorption onto Mn(II)/O-vacancy active centres generates very reactive surface oxygen-species boosting the efficiency of composite MnCeOx catalysts in the CWAO of phenol.

Effect of cerium ions in Ce-Doped ZnO nanostructures on their photocatalytic and picric acid chemical sensing

Nanostructured ZnO doped with different Ce precursor concentrations (1, 5 and 10 mol%) has been prepared via co-precipitation method and tested for their photocatalytic and chemical sensing performances toward methyl orange (MO) and picric acid (PA) chemicals, respectively. After addition of Ce dopant, the spherical morphology of ZnO particles changed to a cone-like structure and exhibited the single-phase wurtzite structure, except for the 10 mol % dopant concentration. Blue-shift was detected in 5 mol% Ce doping, and this was found to be the optimum concentration for achieving the maximum dye degradation and sensing performances. The 5 mol% Ce doped ZnO expressed the complete MO degradation under UV light illumination, but the decrease in MO degradation with 10 mol% Ce doped ZnO was suggested to suppress the Ce3+ character in the sample. Facile redox couple Ce3+/Ce4+ appeared to improve the charge separation of Ce-doped ZnO upon UV illumination, forming the basis for release of O2, leading to increased catalytic and PA sensing performances.

Structural changes of Nd- and Ce-doped ammonium diuranate microspheres during the conversion to U1−yLnyO2±x

The structural changes of ammonium diuranate (ADU) microspheres, prepared by the sol–gel route via internal gelation, were investigated during thermal treatments in oxidative and reducing conditions. In particular, in-situ simultaneous thermogravimetric analyses and in-situ high-temperature scanning electron microscopy investigations were carried out on un-doped ADU microspheres, and ADU microspheres doped with 10 mol% neodymium or 10 mol% cerium. Calcination in air caused the surface of the particles to crack, but with increasing temperature up to 900 °C some healing, and additionally, shrinkage occurred. The extent of the fractures and the amount of shrinkage was, however, significantly more pronounced in a particle prepared with a tetravalent Ce precursor, as compared to particles prepared with a trivalent Nd or Ce precursor. The macroscopic behaviour could be related to the release of volatile decomposition products and the calcined compositions were identified as (Ln-doped) α−U3O8by X-ray powder diffraction. During thermal treatment in reducing conditions a transition from a (Ln-doped) α−U3O8phase to a (Ln-doped) UO2±x phase was observed. After exposure to a hydrogen containing gas mixture, this transition occurred rapidly in un-doped particles, and in particles prepared with trivalent Nd or Ce dopant precursors at 700 °C. Despite the fast reduction reaction, severe fractures appeared in the particles above temperatures of 850 °C, indicating that such behaviour is mainly attributed to sintering effects and less to the phase transition. In contrast, a more delayed reduction reaction was observed in particles prepared with a tetravalent dopant precursor and the described effects appeared less severe.