Zinc-cobalt oxide spinels with precursor-controlled degree of inversion

Petrov, Κ.; Markov, L. K.; Ioncheva, R.; Rachev, P.

doi:10.1007/bf01174050

Cited by 13 publications

(4 citation statements)

References 19 publications

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“…With m greater than 0.18, solid Zn m Co 5 - m (OH) 8 (NO 3 ) 2 solutions are formed . All these precursors decompose topotactically below 300 °C, yielding the corresponding M x Co 3 - x O 4 (0 ≤ x ≤ 1; M = Cu, Ni, Zn) binary spinel cobaltites. , Therefore, it is reasonable to expect that more complex M m M‘ n Co 2 - ( m + n ) (OH) 3 NO 3 hydroxide nitrate precursors might convert into M x M‘ y Co 3 - ( x + y ) O 4 ( x = 3 m /2, y = 3 n /2) spinels. In the present paper we report the synthesis and characterization of the ternary precursors Cu m M n Co 2 - ( m + n ) (OH) 3 NO 3 (M = Ni, Zn) and their corresponding Cu x M y Co 3 - ( x + y ) O 4 spinel products obtained by thermolysis of the hydroxide nitrate solid solutions.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Cation Distribution of the Spinel Cobaltites Cu_xM_yCo₃_-₍_x₊_y₎O₄ (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

1999

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A series of hydroxide nitrate solid solutions with a simple layered structure and general formula Cu m M n Co 2-(m+n) (OH) 3 NO 3 , (M ) Ni, Zn) has been synthesized by double jet precipitation technique, from the corresponding aqueous metal nitrate solutions and NaOH. X-ray diffraction, infrared spectroscopy, and thermal analysis studies have shown that they are single phases which decompose thermally at about 200 °C, yielding the corresponding single-phase spinel-type oxides Cu x M y Co 3-(x+y) O 4 (x ) 3m/2, y ) 3n/2). The cation distribution in these complex spinels has been calculated on the basis of the tetrahedral and octahedral M-O distances determined by X-ray Rietveld refinement of their structures.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Cation Distribution of the Spinel Cobaltites Cu_xM_yCo₃_-₍_x₊_y₎O₄ (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

1999

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“…However, considering a mixed occupancy (Al/Ge) between these two sites, the refinements converged to reliable ADPs (Table 1 and Table ), leading to reduce the Rwp from 10 – 12 to 2 – 3%. Such exchanged occupation of cations on two different sides is well‐known for spinel phases 62,78–83 as degree of inversion and depends on thermodynamic parameter at least from the synthesis temperature 78,79,82 . As such, considering the degree of inversion to the alumogermanate mullite‐type O10 phases, the cation distribution can be treated as a dynamic equilibrium according to the following interchange reaction, where octahedral and pyramidal sites are given as superscripted ‘O’ and ‘P’ respectively:

^{normalO} Al +^{normalP} Ge ⇄^{normalO} Ge +^{normalP} Al

…”

Section: Resultsmentioning

confidence: 99%

Aluminum to germanium inversion in mullite‐type RAlGeO₅: Characterization of a rare phenomenon for R = Y, Sm–Lu

et al. 2021

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Mullite-type RMn 2 O 5 (R = Y, rare-earth element) ceramics are of ongoing research attentions because of their interesting crystal-chemical, physical, and thermal properties. We report a detailed structural, spectroscopic and thermal analysis of the series of mullite-type RAlGeO 5 (R = Y, Sm-Lu) phases. Polycrystalline samples are prepared by solid-state synthesis methods. Each sample is characterized by X-ray powder diffraction followed by Rietveld refinements, showing that they are isotypic and crystallize in the space group Pbam. The change of the metric parameters is explained in term of the lanthanide contraction effect. A rare inversion of Al/Ge between octahedral and pyramidal sites have been observed for these mullite-type so called O10 compounds, and the inversion parameter found to be between 0.22(1) and 0.30(1) for different R-cations. The bond distances and their bond valence sums (BVSs) support the respective inversions.Density functional theory (DFT) calculated phonon density of states (PDOS) and electronic band structures are compared for the vibrational and electronic band gap features respectively. Analysis of UV/Vis absorption spectra using both derivation of absorption spectra fitting (DASF) and Tauc's methods demonstrates that each of the RAlGeO 5 O10 compounds is high bandgap semiconductor, possessing direct transition between 4.1(1) and 5.4(1) eV. Both Raman and Fourier transform infrared spectra show clear red shift (quasi-harmonic) of the vibrational wavenumbers with respect to the ionic radii of the R-cations. Selective Raman bands at higher wavenumber region further complement the inversion of Al/Ge between two coordination sites. The higher decomposition temperature of the RAlGeO 5 compounds, compared to those of RMn 2 O 5 phases, is explained in terms of higher bond strength of Al/Ge-O than those of Mn-O. Irrespective to the inversion between Al-and Ge-sites, the decomposition temperature also depends on the type of R-cation in RAlGeO 5 .

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“…The higher the sintering temperature was, the more likely Mo occupied the tetrahedral site. Generally, the site preference of the different cations in spinels can be fine-tuned by adjusting the strain (lattice mismatch), self-doping, and annealing in thin films and selecting suitable precursors, sintering temperature, and nanostructuring in bulk samples. The wealth of the experimental know-how in synthesizing ferrites can undoubtedly come handy in developing thermoelectric TMFe 2 O 4 , especially for nanostructuring as a mean of reducing the lattice thermal conductivity and enhancing thermoelectric response …”

Section: Resultsmentioning

confidence: 99%

High-Performance Thermoelectric Oxides Based on Spinel Structure

Assadi

Moreno

Fronzi

2020

ACS Appl. Energy Mater.

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High-performance thermoelectric oxides could offer a great energy solution for integrated and embedded applications in sensing and electronics industries. Oxides, however, often suffer from low Seebeck coefficient when compared with other classes of thermoelectric materials. In search of highperformance thermoelectric oxides, we present a comprehensive density functional investigation, based on GGA+U formalism, surveying the 3d and 4d transition-metal-containing ferrites of the spinel structure. Consequently, we predict MnFe 2 O 4 and RhFe 2 O 4 have Seebeck coefficients of ∼ ±600 µV K −1 at near room temperature, achieved by light hole and electron doping. Furthermore, CrFe 2 O 4 and MoFe 2 O 4 have even higher ambient Seebeck coefficients at ∼ ±700 µV K −1 . In the latter compounds, the Seebeck coefficient is approximately a flat function of temperature up to ∼ 700 K, offering a tremendous operational convenience. Additionally, MoFe 2 O 4 doped with 10 19 holes /cm 3 has a calculated thermoelectric power factor of 689.81 µW K −2 m −1 at 300 K, and 455.67 µW K −2 m −1 at 600 K. The thermoelectric properties predicted here can bring these thermoelectric oxides to applications at lower temperatures traditionally fulfilled by more toxic and otherwise burdensome materials.

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Zinc-cobalt oxide spinels with precursor-controlled degree of inversion

Cited by 13 publications

References 19 publications

Synthesis and Cation Distribution of the Spinel Cobaltites Cu_xM_yCo₃_-₍_x₊_y₎O₄ (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

Synthesis and Cation Distribution of the Spinel Cobaltites Cu_xM_yCo₃_-₍_x₊_y₎O₄ (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

Aluminum to germanium inversion in mullite‐type RAlGeO₅: Characterization of a rare phenomenon for R = Y, Sm–Lu

High-Performance Thermoelectric Oxides Based on Spinel Structure

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Zinc-cobalt oxide spinels with precursor-controlled degree of inversion

Cited by 13 publications

References 19 publications

Synthesis and Cation Distribution of the Spinel Cobaltites CuxMyCo3-(x+y)O4 (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

Synthesis and Cation Distribution of the Spinel Cobaltites CuxMyCo3-(x+y)O4 (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

Aluminum to germanium inversion in mullite‐type RAlGeO5: Characterization of a rare phenomenon for R = Y, Sm–Lu

High-Performance Thermoelectric Oxides Based on Spinel Structure

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Synthesis and Cation Distribution of the Spinel Cobaltites Cu_xM_yCo₃_-₍_x₊_y₎O₄ (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

Synthesis and Cation Distribution of the Spinel Cobaltites Cu_xM_yCo₃_-₍_x₊_y₎O₄ (M = Ni, Zn) Obtained by Pyrolysis of Layered Hydroxide Nitrate Solid Solutions

Aluminum to germanium inversion in mullite‐type RAlGeO₅: Characterization of a rare phenomenon for R = Y, Sm–Lu