Crystal growth and thermodynamic investigation of Bi2M2+O4 (M = Pd, Cu)

Wolff, Nora; Klimm, D.; Habicht, Klaus; Fritsch, Katharina

doi:10.1039/d1ce00220a

Cited by 5 publications

(5 citation statements)

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“…Figure 6 also clearly shows that excessive CuO phase precipitates at the grain boundaries as the amount of Cu ions exceeds the solubility limit of KNN when y ⩾ 1.5 mol%. The reported phase diagram 40,41) and previous studies on CuO doping in KNN 38,42) suggest that the CuO phase exists as a liquid phase under atmospheric oxygen partial pressure at 1020 °C-1060 °C at which the coarsening of the KNN single crystals have been observed. In general, the liquid phase present at grain boundaries accelerates grain growth through the promoting elemental diffusion.…”

Section: Sn1015-3mentioning

confidence: 68%

“…1 and 2 was not detected in the calcined powder. From the phase diagram of the CuO and Cu 2 O system, 40) Cu 2 O is likely to be generated above 1040 °C. Cu 2 O, which is formed by a partial phase transition of a large amount of CuO segregated near the crystal growth interface under elevated temperature, acts as the liquid phase, which promotes the crystal growth in the same manner as CuO.…”

Section: Sn1015-3mentioning

confidence: 99%

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Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO₃ single crystals

Morimoto

Shimono

Yoshiichi

et al. 2022

Jpn. J. Appl. Phys.

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We investigated the effects of 0.5 mol% to 6.0 mol% CuO addition on crystal growth by the rapid solid-state crystal growth method to synthesize large unitary rectangular (K,Na)NbO3 (KNN) single crystals several square centimeters within 24 h. X-ray photoelectron spectroscopy and X-ray powder diffraction measurements revealed that CuO and Cu2O segregated in the region near the coarsened single crystal/polycrystal boundary. A positive correlation between crystal growth and the addition of CuO up to 1.5 mol% was observed; however, for CuO amounts larger than 1.5 mol%, this correlation became negative. To investigate these phenomena, a high-precision synchrotron powder diffraction measurement was performed. Significant precipitation of the CuO phase was detected in the calcined powders with a CuO addition larger than 1.5 mol%. The effects of this precipitation on the growth mechanism for coarsening the single crystals were discussed.

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Section: Sn1015-3mentioning

confidence: 68%

Section: Sn1015-3mentioning

confidence: 99%

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO₃ single crystals

Morimoto

Shimono

Yoshiichi

et al. 2022

Jpn. J. Appl. Phys.

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“…Most experimental articles describe phase diagrams for Bi 2 O 3 –CuO systems or similar two- or three-component systems. − They all consider different stoichiometric mixtures and liquid phases, making it difficult to compare the same stability region of solid stoichiometric CBO.…”

Section: Resultsmentioning

confidence: 99%

Theoretical Investigations on the Surface Stability of CuBi₂O₄ and CuFeO₂

Beßner,

Bogenrieder,

Neuhoff

et al. 2024

J. Phys. Chem. C

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CuBi 2 O 4 and CuFeO 2 are p-type semiconductors that recently have been suggested as profitable photocathode materials for photo(electro)chemical reactions, such as water splitting or carbon dioxide reduction. Currently, not much is known of the surfaces of CuBi 2 O 4 and CuFeO 2 , although surface properties are crucial for a better understanding of the photocatalytic performance. In this work, we perform electronic structure simulations using DFT + U to investigate the structures, electronic properties, and thermodynamic stability of CuFeO 2 and CuBi 2 O 4 surfaces. The calculations indicate higher stabilities for stoichiometrically terminated (001)-CuBi 2 O 4 and (012)-CuFeO 2 surfaces. Beyond that, the Bader charge analysis of surfaces with Cu-rich terminations yields charge fluctuations among multiple surface layers, giving rise to lower stability of Fe-deficient surfaces. In contrast, both materials' Cu-deficient surface terminations cover greater stability regions. The density of states shows surface states at the valence band maximum and conduction band minimum for cation-deficient surface terminations which can enable the separation of photogenerated electron−hole pairs. These effects could facilitate or complicate higher absorption efficiency for cation-deficient surfaces. Our results emphasize the importance of surface terminations for a better understanding of electronic properties and exhibit further theoretical findings of CuFeO 2 and CuBi 2 O 4 .

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“…Continuously, the melt must absorb O 2 (gas) from the atmosphere to facilitate the Me n /Me n+1 equilibrium in the melt, because the latter ion is permanently incorporated into the crystal. Possibly, this limits the maximum growth rate, but nevertheless, the growth of crystals with a high oxidation state, such as the initial example Ca 2 Fe 2 O 5 [29], or Bi 2 CuO 4 [44], is possible without severe problems. Figure 5b shows the opposite case where the average oxidation level of the crystal is lower than that of the melt.…”

Section: Discussionmentioning

confidence: 99%

“…With simultaneous DTA/TG measurements, it was found that melting is accompanied by a positive TG step, and the magnitude of this step ( 0.2%) is almost proportional to the oxygen concentration in the atmosphere during the measurement [40,41] 3+ 2 Pd 2+ O 4 , the mass rises, due to oxygen incorporation and partial oxidation of Cu + or Pd 0 to the two-valent state. Bi 2 CuO 4 single crystals up to 6 mm in diameter and 7 cm in length were obtained by OFZ [44].…”

mentioning

confidence: 99%

On Thermodynamic Aspects of Oxide Crystal Growth

Klimm

Wolff

2022

Applied Sciences

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Several metal oxide compounds, especially those containing metals possessing several valence states, are able to absorb or release oxygen under suitable thermodynamic conditions. Such behavior is found often in systems containing oxides of transition metals. It is important to note that the equilibrium oxidation level of those metal oxides can depend on the aggregation state, which may significantly impede crystal growth processes from the melt. If during the melt growth of such oxide crystals, the average valence state of the oxides is different in the molten and solid state, then crystallization is connected with the absorption of free oxygen from the ambient gas, or with the release of free oxygen into it. This phenomenon can be detected by simultaneous DTA/TG measurements and can deteriorate the stability of crystal growth. This holds especially if the average valence in the solid is smaller than in the melt, because oxygen release can lead to bubble formation at the crystallization front.

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Crystal growth and thermodynamic investigation of Bi₂M²⁺O₄ (M = Pd, Cu)

Abstract: The work establishes a connection between the thermodynamics and crystal growth of Bi2M2+O4 and reveals new insights into the description and understanding of the growth process and its optimization.

Cited by 5 publications

References 41 publications

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO₃ single crystals

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO₃ single crystals

Theoretical Investigations on the Surface Stability of CuBi₂O₄ and CuFeO₂

On Thermodynamic Aspects of Oxide Crystal Growth

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Crystal growth and thermodynamic investigation of Bi2M2+O4 (M = Pd, Cu)

Abstract: The work establishes a connection between the thermodynamics and crystal growth of Bi2M2+O4 and reveals new insights into the description and understanding of the growth process and its optimization.

Cited by 5 publications

References 41 publications

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO3 single crystals

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO3 single crystals

Theoretical Investigations on the Surface Stability of CuBi2O4 and CuFeO2

On Thermodynamic Aspects of Oxide Crystal Growth

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Crystal growth and thermodynamic investigation of Bi₂M²⁺O₄ (M = Pd, Cu)

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO₃ single crystals

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO₃ single crystals

Theoretical Investigations on the Surface Stability of CuBi₂O₄ and CuFeO₂