Quantifying oxygen vacancies in neodymium and samarium doped ceria from heat capacity measurements

Neilsen, Grace; Rosen, Peter F.; Dickson, Matthew S.; Popovic, Marko; Schliesser, Jacob; Hansen, Lee D.; Navrotsky, Alexandra; Woodfield, Brian F.

doi:10.1016/j.actamat.2020.02.055

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…This equation is very similar to eq except that it substitutes the Schottky term in eq with a linear term. Linear terms denote electronic heat capacity in metals, but we assumed that it represented the contribution of lattice vacancies to the heat capacity in these samples. , We initially fit the [Zn–Al–X] LDH samples using eq , but this fit resulted in unacceptable systematic deviations. Equation provided a much better fit using a Schottky term to account in these data.…”

Section: Resultsmentioning

confidence: 99%

Role of Anions in Stabilizing the [Zn–Al] Layered Double Hydroxides: A Thermodynamic Study

et al. 2023

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Room-temperature acid solution calorimetry, high-temperature oxide melt solution calorimetry, and low-temperature heat capacity measurements were employed to calculate the thermodynamic stabilities of the [Zn–Al–X] layered double hydroxides (LDH) containing different anions (X = Cl–, CO3 2–, and SO4 2–). Cryogenic heat capacity measurements demonstrated a Schottky-type anomaly in the heat capacity of all three LDHs below 11 K. This anomaly is attributed to the tunneling of protons between adjacent oxygen atoms in the LDH interlayer as this creates an energy system similar to a two-level system modeled with a Schottky term. These heat capacity measurements were also used to determine vibrational entropies which, when combined with configurational entropies, provide standard entropies of these LDHs. Enthalpies of formation of LDHs from binary components were determined and combined with the entropies of formation to calculate Gibbs free energies. Based on these values, the order of stability is [Zn–Al–SO4] > [Zn–Al–CO3] > [Zn–Al–Cl]. This trend results from a combination of the interlayer spacing, amount of water in the interlayer, interactions among the interlayer species, and interactions between the metal hydroxide layer and the interlayer.

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Section: Resultsmentioning

confidence: 99%

Role of Anions in Stabilizing the [Zn–Al] Layered Double Hydroxides: A Thermodynamic Study

et al. 2023

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“…According to this relation the number of vacancies for the flux sample should be smaller, contradicting the TGA/DTA data collected. The ordering of these vacancies can have an impact on the predictability of this theory, which would indicate the presence of defect clustering for these samples …”

Section: Resultsmentioning

confidence: 99%

“…The ordering of these vacancies can have an impact on the predictability of this theory, which would indicate the presence of defect clustering for these samples. 55 Thus, the more exotic phenomenon for the proposed linear term is ruled out by plotting the combined Debye and Einstein phonon contribution. One can see this fits the data almost identically to the linear fit.…”

Section: ■ Methodsmentioning

confidence: 99%

Optimization of PbTiO₃ Single Crystals with Flux and Laser Floating Zone Method

Pressley

Sinha

Vivanco

et al. 2022

Crystal Growth & Design

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PbTiO 3 is an established high temperature ferroelectric and component of multiferroic devices. Single crystal growth of clean PbTiO 3 has largely been limited to flux growth, in part due to the volatility of PbTiO 3 near the melting point. We demonstrate the ability to grow single crystals of PbTiO 3 using the laser diode floating zone technique. Crystal quality is examined using Laue, powder, and single crystal X-ray diffraction. Low temperature specific heat and annealing experiments using thermogravimetric analysis/differential thermal analysis were used to compare the disorder and vacancies generated in the laser diode floating zone with those produced by flux growth. Samples grown using the floating zone method showed minimal oxygen deficiency, while samples grown via flux had a higher density of vacancies and metal impurities (determined using glow discharge mass spectrometry), resulting in room temperature ferromagnetic behavior. The use of laser diodes as a heating source in the optical floating zone technique is essential in the stability of the zone growth and could be applied for production and zone refinement of other volatile materials.

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“…Indeed, REM cations possess high ionic radii (Sm 3+ , 0.958 Å; Eu 3+ , 0.947 Å; Gd 3+ , 0.938 Å) [48], considerably higher with respect to Ni 2+ (0.69 Å) [48] and Al 3+ (0.535 Å) [48]. Therefore, the substitution of the nickel cations generates the defects on cationic lattice sites and additionally may force oxygen vacancies [49][50][51]. Consequently, the induced structural disorder is responsible for the increased particles sizes and thus smaller surface area.…”

Section: Photocatalytic Activity Studymentioning

confidence: 99%

Rare-Earth Metals-Doped Nickel Aluminate Spinels for Photocatalytic Degradation of Organic Pollutants

et al. 2020

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Visible-light-activated photocatalysts based on samarium-doped, europium-doped, and gadolinium-doped nickel aluminates (SmNA, EuNA, GdNA) were synthesized. The spinel crystalline structures of the doped mixed metal oxides were demonstrated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The presence of the rare-earth metals (REMs) was confirmed by the energy-dispersive X-ray (EDX) studies. Ultraviolet-visible-near-infrared (UV-Vis-NIR) spectra revealed that the REMs-doped catalysts absorb in the full solar spectrum range covering both visible and near infrared wavelengths. Scanning electron microscopy (SEM) visualized the profound morphological alterations of the doped nickel aluminate samples. Consequently, the pore volume and the Brunauer-Emmett-Teller (BET) surface area decreased, while nanoparticles sizes increased. Fourier-transform infrared spectroscopy (FTIR) exposed that surfaces of REMs-doped nickel aluminates are rich in hydroxyl groups. Finally, the photocatalytic performance was notably increased through doping nickel aluminate (NA) with REMs; the highest activity was observed for EuNA.

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Quantifying oxygen vacancies in neodymium and samarium doped ceria from heat capacity measurements

Cited by 9 publications

References 19 publications

Role of Anions in Stabilizing the [Zn–Al] Layered Double Hydroxides: A Thermodynamic Study

Role of Anions in Stabilizing the [Zn–Al] Layered Double Hydroxides: A Thermodynamic Study

Optimization of PbTiO₃ Single Crystals with Flux and Laser Floating Zone Method

Rare-Earth Metals-Doped Nickel Aluminate Spinels for Photocatalytic Degradation of Organic Pollutants

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Quantifying oxygen vacancies in neodymium and samarium doped ceria from heat capacity measurements

Cited by 9 publications

References 19 publications

Role of Anions in Stabilizing the [Zn–Al] Layered Double Hydroxides: A Thermodynamic Study

Role of Anions in Stabilizing the [Zn–Al] Layered Double Hydroxides: A Thermodynamic Study

Optimization of PbTiO3 Single Crystals with Flux and Laser Floating Zone Method

Rare-Earth Metals-Doped Nickel Aluminate Spinels for Photocatalytic Degradation of Organic Pollutants

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Product

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About

Optimization of PbTiO₃ Single Crystals with Flux and Laser Floating Zone Method