Thermal expansion of FeWO$_4$ (Ferberite) and FeWO$_4$:Fe$_2$WO$_6$ (7:1): a comparative X-ray and neutron diffraction study

D. Errandonea; D. Vie; E. Matesanz; J. Gonzalez-Platas; L. Ca\~nadillas-Delgado; O. Fabelo

arxiv: 2605.14792 · v1 · pith:RDKRCXDHnew · submitted 2026-05-14 · ❄️ cond-mat.mtrl-sci

Thermal expansion of FeWO₄ (Ferberite) and FeWO₄:Fe₂WO₆ (7:1): a comparative X-ray and neutron diffraction study

O. Fabelo , L. Ca\~nadillas-Delgado , D. Vie , E. Matesanz , J. Gonzalez-Platas , D. Errandonea This is my paper

Pith reviewed 2026-06-30 20:24 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci

keywords thermal expansionFeWO4ferberiteX-ray diffractionneutron diffractionlattice parametersthermodynamic modelstungsten compounds

0 comments

The pith

The FeWO4:Fe2WO6 mixture shows a thermal expansion coefficient roughly 40 percent smaller than pure ferberite, with a reduced reference volume.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper measures lattice parameters of natural FeWO4 ferberite and a synthetic 7:1 mixture with Fe2WO6 from 2 K to 1123 K using single-crystal X-ray, powder X-ray, and neutron diffraction. It fits the unit-cell volume data to the Kroll and Berman thermodynamic models and reports that the mixed phase expands substantially less and starts from a smaller reference volume. A sympathetic reader would care because reliable thermal expansion values matter for predicting dimensional stability in minerals and synthetic materials exposed to wide temperature swings. The authors link the observed difference to possible microstructural or phase-coexistence effects inside the samples.

Core claim

Significant differences are observed between the behavior of ferberite and FeWO4:Fe2WO6, which has a ~40% smaller thermal expansion coefficient and a reduced reference volume. All datasets are well reproduced within their respective temperature intervals by the Kroll and Berman approaches as implemented in EoSFit7.

What carries the argument

High-precision lattice parameters obtained from combined single-crystal X-ray, powder X-ray, and neutron powder diffraction, fitted to physically based thermodynamic models for unit-cell volume versus temperature.

If this is right

The Kroll and Berman models describe the temperature dependence of the unit-cell volume for both phases across the full measured range.
Phase coexistence inside the mixed sample produces a measurably lower thermal expansion coefficient and smaller reference volume.
The results supply a complete set of lattice-parameter data for FeWO4-based materials from cryogenic to above 1100 K.
Microstructural features can alter the effective thermal expansion of tungsten-based compounds without changing the average composition.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Controlling the ratio of Fe2WO6 could offer a route to tune the thermal expansion of related iron-tungsten oxides for high-temperature use.
Natural ferberite samples may show different expansion behavior depending on their geological history of phase mixing or defect density.
Repeating the measurements on other mixture ratios would test whether the 40 percent reduction scales continuously with Fe2WO6 content.

Load-bearing premise

The measured differences in expansion and volume arise from intrinsic microstructural or phase-coexistence effects in the samples rather than from experimental artifacts, impurities, or unmodeled temperature-dependent changes in diffraction conditions.

What would settle it

Performing identical diffraction measurements on a pure synthetic FeWO4 crystal or powder and checking whether its thermal expansion coefficient matches the natural ferberite value or the smaller mixed-phase value.

Figures

Figures reproduced from arXiv: 2605.14792 by D. Errandonea, D. Vie, E. Matesanz, J. Gonzalez-Platas, L. Ca\~nadillas-Delgado, O. Fabelo.

**Figure 1.** Figure 1: View of the single crystal of ferberite used in the SC-XRD experiment in the Bruker D8 diffractometer. 2.3 X-ray powder diffraction X-ray diffraction measurements on the powdered ferberite sample and synthetic FeWO4 were carried out using an X’Pert diffractometer equipped with Cu Kα radiation and an X’Celerator detector at Universidad Complutense de Madrid. Low-temperature measurements in the 15–300 K rang… view at source ↗

**Figure 2.** Figure 2: Temperature evolution of the unit-cell volume for the ferberite sample determined by X-ray diffraction. Single-crystal measurements (circles) were collected between 40 and 500 K, while powder X-ray diffraction measurements on the corresponding ground sample (squares) were [PITH_FULL_IMAGE:figures/full_fig_p007_2.png] view at source ↗

**Figure 3.** Figure 3: (Top) Rietveld refinement of the neutron powder diffraction pattern of synthetic FeWO₄ measured at D20 at 300 K (λ = 1.54119(3) Å). The experimental data and calculated profile are shown as red and black lines, respectively, while the blue curve represents the difference. Vertical green, orange, and red ticks indicate the Bragg reflection positions of the different phases. The second phase corresponds to V… view at source ↗

**Figure 4.** Figure 4: Results from the experiments performed in synthetic FeWO4. Volume behavior between 2 and 470 K measured using neutrons in D20 diffractometer at ILL (circles) and 15-473 K results obtained from powder XRD (squares). Error bars are smaller than symbols. The lines show the fit of the data to Kroll model. A reduced unit-cell volume in the synthesized material could in principle indicate either the presence of … view at source ↗

read the original abstract

The thermal expansion of natural FeWO$_4$ (ferberite) and synthetic FeWO$_4$:Fe$_2$WO$_6$ (7:1) was investigated over the 2-1123 K temperature range combining single-crystal and powder X-ray diffraction together with neutron powder diffraction. High-precision lattice parameters were obtained for both samples. The temperature dependence of the unit-cell volume was analysed using physically based thermodynamic models, including the Kroll and Berman approaches as implemented in EoSFit7. All datasets are well reproduced within their respective temperature intervals. However, significant differences are observed between the behavior of ferberite and FeWO$_4$:Fe$_2$WO$_6$, which has a \~40% smaller thermal expansion coefficient and a reduced reference volume. Possible origins, including microstructural and phase-coexistence effects, are discussed. The results provide a comprehensive description of the thermal expansion behavior of FeWO$_4$ across a wide temperature range.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper delivers new comparative lattice data showing ~40% lower thermal expansion in the synthetic FeWO4:Fe2WO6 mixture versus natural ferberite, backed by multi-technique diffraction over 2-1123 K.

read the letter

The key point here is straightforward: they measured high-precision lattice parameters for natural ferberite and a 7:1 synthetic mix with Fe2WO6 using single-crystal XRD, powder XRD, and neutron diffraction across 2-1123 K, then fit the volumes with standard Kroll and Berman models in EoSFit7. Both datasets fit the models well, and the mixture shows a roughly 40% smaller thermal expansion coefficient plus a smaller reference volume.

What stands out as new is the direct side-by-side comparison on these exact compositions over that full temperature span, which had not been reported before. The work does a solid job on the experimental side by combining techniques for better precision and covering both very low and high temperatures where data are often missing.

The soft spots are mostly in the presentation and interpretation. The abstract gives no error bars, no tables of raw parameters, and limited detail on sample purity or how they handled possible impurities or phase coexistence. That makes it hard to judge how much of the 40% difference is intrinsic versus tied to microstructure or experimental conditions. The discussion of origins is mentioned but not expanded in the summary we have, so the causal claim stays observational rather than tightly pinned down.

This is the kind of paper that matters for people who need concrete numbers for tungsten minerals in materials applications or mineral physics, not for anyone looking to shift broad theory. A reader working on thermal properties of oxides or specific Fe-W compounds would get usable data from it.

I would send it to peer review. The measurements are the main contribution, the methods are appropriate, and the difference is large enough to be worth checking in detail even if some sample characterization needs tightening.

Referee Report

1 major / 0 minor

Summary. The manuscript reports a comparative study of the thermal expansion of natural FeWO₄ (ferberite) and synthetic FeWO₄:Fe₂WO₆ (7:1) over 2–1123 K, using single-crystal and powder X-ray diffraction together with neutron powder diffraction. High-precision lattice parameters are extracted for both samples and fitted to the Kroll and Berman thermodynamic models as implemented in EoSFit7. The synthetic mixture is reported to exhibit a ~40% smaller thermal expansion coefficient and a reduced reference volume relative to natural ferberite; possible microstructural and phase-coexistence origins are discussed.

Significance. If the reported differences are confirmed to be intrinsic, the work supplies a wide-temperature-range experimental dataset on FeWO₄ thermal expansion obtained by complementary diffraction methods and physically motivated model fits. Such data are useful for mineralogical and materials applications where phase coexistence or microstructure may modulate thermal response.

major comments (1)

[Abstract] Abstract: the central claim of a ~40% smaller thermal expansion coefficient for the synthetic sample is stated without error bars, tabulated raw lattice parameters, sample-purity characterization, or explicit data-reduction steps. These omissions make the magnitude and statistical significance of the difference only partially verifiable from the information provided.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive assessment and the helpful comment on the abstract. We address the point below and agree that a minor revision to the abstract will improve standalone clarity while preserving the manuscript's focus.

read point-by-point responses

Referee: [Abstract] Abstract: the central claim of a ~40% smaller thermal expansion coefficient for the synthetic sample is stated without error bars, tabulated raw lattice parameters, sample-purity characterization, or explicit data-reduction steps. These omissions make the magnitude and statistical significance of the difference only partially verifiable from the information provided.

Authors: The detailed lattice parameters (with e.s.d.s from the refinements), sample synthesis and purity characterization (via chemical analysis and phase identification), and data-reduction procedures are fully described in the Experimental Methods and Results sections, with all fitted coefficients and uncertainties reported in the tables and figures. The abstract follows standard practice as a concise summary of the key finding. To improve verifiability of the central claim directly from the abstract, we will revise it to include approximate uncertainties on the thermal expansion coefficients and the percentage difference (derived from the Kroll/Berman model fits), while directing readers to the full datasets and supplementary tables for raw values. revision: yes

Circularity Check

0 steps flagged

No significant circularity; results are direct experimental observations

full rationale

The paper's central claims consist of high-precision lattice parameters measured via combined XRD and neutron diffraction over 2-1123 K, followed by post-hoc fitting of standard Kroll and Berman models (implemented in EoSFit7) to the volume-temperature data. The reported ~40% difference in thermal expansion coefficient and reduced reference volume between the two samples is an empirical observation from the measured datasets, with no feedback from the fits into the raw measurements or reported differences. No self-citations, ansatzes, or uniqueness theorems are invoked to derive or justify the load-bearing results; the models are applied after data collection and serve only for parameterization. The derivation chain is therefore self-contained against external benchmarks (diffraction data), with no reduction of predictions or claims to fitted inputs by construction.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

Analysis rests on fitting measured volumes to two established thermodynamic models whose parameters are adjusted to each dataset; no new physical entities are introduced.

free parameters (1)

reference volume and thermal-expansion coefficients
Fitted separately for each sample inside the Kroll and Berman implementations in EoSFit7 to reproduce the observed volume-temperature curves.

axioms (1)

domain assumption The Kroll and Berman models, as coded in EoSFit7, correctly capture the temperature dependence of unit-cell volume for these materials.
Invoked to analyze all datasets and to claim that both are well reproduced within their temperature intervals.

pith-pipeline@v0.9.1-grok · 5755 in / 1259 out tokens · 28140 ms · 2026-06-30T20:24:18.647719+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

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Drebushchak, V . A. (2020) J. Thermal Anal. Calor. 142, 1097–1113. S1 SUPPORTING INFORMATION Thermal expansion of FeWO₄ (Ferberite) and FeWO4:Fe2WO6 (7:1): a comparative X-ray and neutron diffraction study O. Fabelo 1, L. Cañadillas -Delgado1, D. Vie 2, E. Matesanz 3, J. Gonzalez- Platas4, and D. Errandonea5,* 1 Institut Laue-Langevin, 71 avenue des Marty...

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[1] [1]

(2026) J

Muñoz, A., Radescu, S., Mujica, A., & Errandonea, D. (2026) J. Phys. Chem. 130, 9, 3201– 3225

2026

[2] [2]

(1968) Zeitschrift für Kristallographie 127, 61-72

Cid-Dresdner, H. (1968) Zeitschrift für Kristallographie 127, 61-72

1968

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E., López-Moreno, S., Turnbull, R., Manjón, F

Diaz-Anichtchenko, D., Aviles-Coronado, J. E., López-Moreno, S., Turnbull, R., Manjón, F . J., Popescu, C., & Errandonea D. (2024) Inorg. Chem. 63, 6898-6908

2024

[4] [4]

A., Lorenz, T., & Khomskii, D

Heyer, O., Hollmann, N., Klassen, I., Jodlauk, S., Bohatý, L., Becker, P ., Mydosh, J. A., Lorenz, T., & Khomskii, D. (2006= J. Phys.: Condens. Matter 18, L471−L475

2006

[5] [5]

(2003) Eur

García-Matres, E., Stüßer, N., Hofmann, M., & Reehuis, M. (2003) Eur. Phys. J. B 32, 35−42

2003

[6] [6]

I., Daou, R., Chang, C

Maignan, A., Schmidt, M., Prots, Y ., Lebedev, O. I., Daou, R., Chang, C. F ., Kuo, C. Y ., Hu, Z., Chen, C. T ., Weng, C. C., Altendorf , S. G., Tjeng, L. H., & Grin, Y . (2022) Chem. Mat. 34, 789-797

2022

[7] [7]

(2012) Eur

Kroll H., Kirfel A., Heinemann R., & Barbier B. (2012) Eur. J. Miner. 24, 935-956

2012

[8] [8]

Salje E. K. H., Wruck B., & Thomas H. (1991) Zeitschrift für Physik B 82, 399-404

1991

[9] [9]

Berman R. G. (1988) J. Petrol. 29, 445-522

1988

[10] [10]

(2024) J

Fabelo, O., Gonzalez-Platas, J., Savvin, S., Botella, P ., & Errandonea, D. (2024) J. Appl. Phys. 136, 175901

2024

[11] [11]

Gonzalez-Platas, J., Alvaro, M., Nestola, F ., Angel, R. 2016, J. Appl. Cryst, 49, 1377-1382

2016

[12] [12]

Bruker. SAINT. Version 8.34a. Bruker AXS Inc. Madison, Wisconsin, EEUU (2014)

2014

[13] [13]

Le Bail, A., Duroy, H., & Fourquet, J. L. (1998) Mater. Res. Bull. 23, 447-452

1998

[14] [14]

(1993) Physica B 192, 55-69

Rodríguez-Carvajal, J. (1993) Physica B 192, 55-69

1993

[15] [15]

T. C. Hansen, P . F . Henry, H. E. Fischer, J. Torregrossa, and P . Convert, Meas. Sci. Technol., 2008, 19, 034001

2008

[16] [16]

W., Cox, D

Finger, L. W., Cox, D. E., & Jephcoat, A. P . (1994) J. Appl. Cryst. 27, 892–900

1994

[17] [17]

Available in the online ILL repository, https://code.ill.fr/fabelo/panda

[18] [18]

Qin, W., Nagase, T., Umakoshi, Y ., & Szpunar, J. A. (2008) Phil. Mag. Letters 88, 169–179

2008

[19] [19]

Akhlaghi, M., Steiner, T., Meka, S. R. & Mittemeijer, E. J. (2016) J. Appl. Cryst. 49, 69-77

2016

[20] [20]

L., & Tuan, W.H

Hsieh, C. L., & Tuan, W.H. & Mater. Sci. Eng. A 425, 349–360

[21] [21]

(2009) Mat

Takeda, M., Onishi, T., Nakakubo, S., & Fujimoto, S. (2009) Mat. Trans. 50, 2242-2246

2009

[22] [22]

Zou, Y ., Wang, P ., Li, Y ., Chen, H., Zhou, C., & Irifune, T, (2025) iScience 28, 111905

2025

[23] [23]

(2018) Ceram

Yang, G., Liu, X., Sun, X., Liang, E., & Zhang, W. (2018) Ceram. Int. 44, 22032-22035

2018

[24] [24]

Shannon, R. D. (1976) Acta Crystallogr. A 32, 751–767

1976

[25] [25]

Errandonea, D., & Manjon, F . J. (2008) Progress in Materials Science 53, 711-773. 20

2008

[26] [26]

A., Dubrovinsky, L

Dubrovinskaia, N. A., Dubrovinsky, L. S., Saxena, S. K., & Sundman, B. (1997) Calphad 21, 497-508

1997

[27] [27]

Drebushchak, V . A. (2020) J. Thermal Anal. Calor. 142, 1097–1113. S1 SUPPORTING INFORMATION Thermal expansion of FeWO₄ (Ferberite) and FeWO4:Fe2WO6 (7:1): a comparative X-ray and neutron diffraction study O. Fabelo 1, L. Cañadillas -Delgado1, D. Vie 2, E. Matesanz 3, J. Gonzalez- Platas4, and D. Errandonea5,* 1 Institut Laue-Langevin, 71 avenue des Marty...

2020