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[Sr2FeVO6-comment-210823.doc](https://mdr.nims.go.jp/filesets/b057fd8d-4e49-4059-89e5-e1fb65229dbc/download)

## Creator

[Alexei A. Belik](https://orcid.org/0000-0001-9031-2355)

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[In Copyright](http://rightsstatements.org/vocab/InC/1.0/)

## Other metadata

[Comments on the paper “Multifunctional feature of double perovskite strontium iron vanadate for storage device”](https://mdr.nims.go.jp/datasets/0f432d24-0c35-4751-98d3-ef280df225e4)

## Fulltext

Comments on the paper “Multifunctional feature of double perovskite strontium iron vanadate for storage device”Alexei A. BelikInternational Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, JapanE-mail: Alexei.Belsik@nims.go.jpAbstractBy these comments we would like to bring attention of the scientific community to erroneous results reported in the commented paper on the double perovskite “Sr2FeVO6”. We showed that the claimed compound does not exist (at least, when prepared at ambient pressure and in air) either in the double perovskite modification or any other modifications. We showed that a mixture of Sr3(VO4)2, cubic perovskite SrFeO3−(, and SrFe12O19 was obtained in the commented paper instead. The observed room-temperature ferromagnetic properties are most probably originated from the presence of ferrimagnetic SrFe12O19.Keywords: double perovskites; X-ray diffraction; phase analysis; lattice parameters; errorsS. Bhattacharjee et al. [1] reported the conventional solid-state synthesis in air of the claimed double perovskite “Sr2FeVO6”. The synthesis was performed from a stoichiometric mixture of 4SrCO3, Fe2O3, and V2O5 at 1473 K for 5 h (pellets for measurements were additionally annealed at 1523 K for 6 h). The authors used a commercial indexing program to index reflections observed on an experimental X-ray diffraction pattern. They found a monoclinic cell with a = 6.602 Å, b = 13.764 Å, c = 5.382 Å, and β = 106.770(, which could explain nearly all observed reflections as claimed in Table 1 of Ref. [1]. Therefore, the authors concluded that a single-phase sample with the Sr2FeVO6 composition was prepared. Then, the obtained sample was intensively characterized by different methods including the observation of room-temperature ferromagnetic-like properties through the observation of M-H hysteresis loop.We tried to reproduce the results reported in Ref. [1]. We annealed a stoichiometric mixture of 4SrCO3, Fe2O3, and V2O5 at 973 K for 12 h + 973 K for 60 h + 1073 K for 18 h + 1173 K for 16 h as powder in an Al2O3 crucible, where the sample was reground after each step marked by “+”, and X-ray powder diffraction data were measured to follow the evolution of the reaction. X-ray powder diffraction data were collected at room temperature with a RIGAKU MiniFlex600 diffractometer [CuK( radiation; a 2( range of 10(80(; a step of 0.02(, and scan speed of 3 (/min]. We obtained nearly the same X-ray diffraction pattern (after the final annealing at 1173 K) as reported on Figure 1 of Ref. [1] (see Figure 1 of this comment) with very good matches of reflection positions even near 80( – this fact shows that zero-shift corrections should be very small (or at least, the same) for both data sets. However, we identified three known phases from our X-ray diffraction pattern: Sr3(VO4)2 (ICDD PDF 29-1318 and 81-1844), cubic perovskite SrFeO3−( (ICDD PDF 40-0905), and SrFe12O19 (ICDD PDF 33-1340). This was further confirmed by the Rietveld fitting using the structural parameters for the corresponding phases (ICSD codes 73258, 91062, and 66402, respectively) (Figure 1b). The Rietveld analysis was performed using the RIETAN-2000 program [2] (we note that the refined zero-shift parameter of 4.0(5)(10(3 was indeed small for our data). The weight fractions of the phases estimated from the refined scale factors in the Rietveld fit were 62 % for Sr3(VO4)2, 27 % for SrFeO3−(, and 11 % for SrFe12O19. No other phases were detected in our sample. However, weak reflections of additional phases were observed in Ref. [1] (for example, a peak indexed as (200) and a peak near 12.1( (Figure 1a)). From the comparison of our X-ray diffraction results we can say that peaks indexed as (050), (032), (242), (143), (403), and (453) belong to cubic perovskite SrFeO3−(; peaks indexed as (220) and (112) are the strongest reflections of SrFe12O19. Therefore, we conclude that a mixture of Sr3(VO4)2, cubic perovskite SrFeO3−(, and SrFe12O19 was investigated in Ref. [1] as a new compound “Sr2FeVO6”. SrFe12O19 is a well-known ferrimagnetic material with a high Curie temperature of 733 K [3] – the presence of this phase could explain the observation of a room-temperature ferromagnetic-like hysteresis loop in Ref. [1].The indexing results reported in Table 1 of Ref. [1] are not correct. The first four reflections were reported to have the exact match between the observed and calculated values (in addition to a few other reflections) – this is an alarming match. Some reflections had a huge difference between the observed and calculated values, for example, the reported (220) reflection had 2( = 30.57( (experimental) and 2( = 31.11( (calculated). Most importantly, the reported list of the observed experimental reflections (Table 1 in Ref. [1]) does not match with the observed experimental pattern (Figure 2). We also tried to perform indexing of the reported experimental data (using 2( values from Table 1 in Ref. [1]) using TREOR [4], but we failed to get any solutions (even when the 30.57( reflection was removed) with reasonable agreement factors. Zero shifts were mentioned above as they could have significant effects of indexing results and indexing success. Therefore, the absence of any phase analysis, a wrong assumption that a single-phase sample was obtained, and a wrong indexing resulted in erroneous results/claims in Ref. [1].Problems with the existence of “Sr2FeVO6” and “Ba2FeVO6” perovskites and solid solutions between them have already been highlighted in the literature [5, 6]. Nevertheless, papers continue to appear with wrong claims about the existence of such compounds [1, 7, 8]. Therefore, further commentaries are needed (as this one) to correct the scientific literature.References[1] S. Bhattacharjee, B Mohanty, R.K. Parida, B.N. Parida, Multifunctional feature of double perovskite strontium iron vanadate for storage device. Mater. Chem. Phys. 275 (2022) 125254.[2] F. Izumi, T. Ikeda, A Rietveld-analysis program RIETAN-98 and its applications to zeolites. Mater. Sci. Forum 321–324 (2000) 198–205.[3] R. C. Pullar, Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics. Prog. Mater. Sci. 57 (2012) 1191–1334.[4] P. E. Werner, L. Eriksson, M. Westdahl, TREOR, a semi-exhaustive trial-and-error powder indexing program for all symmetries. J. Appl. Crystallogr. 18 (1985) 367−370.[5] P. E. Tomaszewski, Comments on the paper on Ca-modified double perovskite Ba2FeVO6 by S. Bhattacharjee et al. and published in Physica B 624 (2022) 413373. Physica B: Physics of Condensed Matter 631 (2022) 413708.[6] P. E. Tomaszewski, Comments on the paper on vanadium based double perovskite BaSrFeVO6 by S. Bhattacharjee et al. and published in "Mat. Sci. Semicon. Proc." 123 (2021) 105503. Mat. Sci. Semicon. Proc. 142 (2022) 106466.[7] Z. W. Wu, K. Yi, Q. K. Tang, J. Y. Gu, X. H. Zhu, Influence of Ba-doping on the structural and physical properties of Sr2−xBaxFeVO6 double perovskites. J. Alloy. Comp. 930 (2023) 167431.[8] S. Bhattacharjee, F. Brahma, R. K. Parida, B. N. Parida, Correction to: Synthesis and characterization of revived double perovskite Ba0.5Sr1.5FeVO6. J. Mater. Sci.: Mater. Electron. 33 (2022) 16710–16711     -505101510 20 30 40 50 60 70 80(a)  (b)  Intensity (counts/10 3 )  2     (deg): Cu K   Figure 1. (a) An experimental X-ray diffraction pattern of a “Sr2FeVO6” sample from Figure 1 of Ref. [1]. (b) Experimental (black crosses), calculated (red line), and difference (blue line at the bottom) room-temperature X-ray diffraction patterns of our sample, which is a mixture of Sr3(VO4)2 (the first row of brown tick marks for possible Bragg reflection positions), cubic perovskite SrFeO3−( (the second row of blue tick marks), and SrFe12O19 (the third row of green tick marks). Figure 1a was reproduced with the permission from Elsevier.   -3391513 18 23 28 33 38 43Intensity (counts/10 3 )  2     (deg): Cu K   (1)  (2)  Figure 2. A fragment (between 13( and 44.4() of an experimental (black crosses) and calculated (red line) X-ray diffraction patterns of our sample (measured with Cu K( radiation). The first row (1) of blue Bragg reflections is taken from Table 1 of Ref. [1] as positions of experimental reflections for “Sr2FeVO6”. The second row (2) of green Bragg reflections shows expected positions for a (primitive) monoclinic cell with a = 6.602 Å, b = 13.764 Å, c = 5.382 Å, and β = 106.770( (for Cu K(1 radiation). There are discrepancies between the experimental pattern and those Bragg positions.Highlights:· A “Sr2FeVO6” perovskite was attempted to synthesize in air.· A mixture of Sr3(VO4)2, SrFeO3−(, and SrFe12O19 was obtained.· SrFe12O19 ferrimagnet is responsible to room-temperature magnetic properties.2