# Fileset

[Ba3Bi2MoO9-comment-030424.doc](https://mdr.nims.go.jp/filesets/88f47049-5174-4402-ab93-50de9eef9bbf/download)

## Creator

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

## Rights

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

## Other metadata

[Comments on the paper “Development of a novel triple perovskite barium bismuth molybdate material for thermistor-based applications”](https://mdr.nims.go.jp/datasets/a9e20ac3-d814-41cf-b2a0-31a91fa0b849)

## Fulltext

Comments on the paper “Influence of Ba-doping on the structural and physical properties of Sr2−xBaxFeVO6 double perovskites”Comments on the paper “Development of a novel triple perovskite barium bismuth molybdate material for thermistor-based applications”Alexei A. BelikResearch Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, JapanE-mail: Alexei.Belik@nims.go.jpAbstractThe title paper (Materials Science & Engineering B 296 (2023) 116616) claimed the preparation and detailed characterization by different methods of a novel triple perovskite compound, Ba3Bi2MoO9. In this comment, it is shown that the phase Ba3Bi2MoO9 does not exist. We show that the absence of the phase analysis resulted in erroneous claims. We demonstrate that the sample in the title paper is mainly a mixture of BaBiO3 and BaMoO4.Keywords: X-ray diffraction; phase analysis; lattice parameters; errorsA recent paper claimed the synthesis of a novel triple perovskite compound with a chemical composition of “Ba3Bi2MoO9“ [1]. “Ba3Bi2MoO9“ was prepared using a conventional solid-state method from a stoichiometric mixture of 3BaCO3, MoO3, and Bi2O3 by annealing in air at 1123 K for 5 h and at 1153 K for 5 h. Reflections on an X-ray powder diffraction pattern of “Ba3Bi2MoO9“ were indexed by the authors in a monoclinic system with lattice parameters of a = 8.95886 Å, b = 7.2799 Å, c = 7.50595 Å, and ( = 104.312(. Therefore, the authors of Ref. [1] concluded that a new nearly single-phase compound was prepared.An X-ray powder diffraction pattern of “Ba3Bi2MoO9“, reported on Figure 1a of Ref. [1], is reproduced on Figure 1a of this commentary. Our phase analysis clearly identified two main phases in “Ba3Bi2MoO9“, which are BaBiO3 (International Center for Diffraction Data (ICDD) Powder Diffraction File (PDF) record 79-1864) and BaMoO4 (PDF 29-1093). There were a number of other weak reflections, but it was difficult to identify them unambiguously. For example, very broad reflections at 2( ( 23.95( (d = 3.71 Å) and 2( ( 34.33( (d = 2.61 Å) could be assigned to BaCO3 (PDF 45-1471). Narrow reflections at 2( ( 27.44( (d = 3.25 Å) and 2( ( 32.58( (d = 2.75 Å) could be assigned to Bi12Mo0.12O18+d (PDF 43-0198). A broad reflection at 2( ( 30.07( (d = 2.97 Å) could be explained by a cubic perovskite-type phase with a = 4.20 Å.Therefore, an ideal reaction should look like:3BaCO3 + MoO3 + Bi2O3 + 0.5O2 = 2BaBiO3 + BaMoO4 (+ 3CO2 ()However, the annealing time or temperature (or both) was not enough to reach phase equilibrium in Ref. [1]; therefore, intermediate and/or initial compounds could remain in small amounts. For example, the reported EDX results in Ref. [1] showed the presence of mainly Bi and O, which could originate from Bi12Mo0.12O18+d.Figure 1b shows calculated X-ray powder diffraction patterns for BaBiO3, BaMoO4, and BaCO3 to illustrate contributions of each phase to the total X-ray powder diffraction pattern reported on Figure 1a. The calculated patterns were obtained using the RIETAN-2000 program [2] and Inorganic Crystal Structure Database (ICSD) for BaBiO3 (code 67077), BaMoO4 (code 136884), and BaCO3 (code 15196). We also used different profile parameters of each phase to reflect different widths of reflections on the experimental X-ray powder diffraction pattern. We note that symmetry, lattice parameters, and oxygen content of BaBiO3 could strongly depend on annealing conditions. The observed reflections for BaBiO3 correspond to a fully stoichiometric sample, which usually crystallizes in space group I2/m (PDF 79-1864).Therefore, a mixture of (partly) known phases was investigated in Ref. [1] instead of a new compound, “Ba3Bi2MoO9”. The authors in Ref. [1] did not perform any standard phase-analysis procedures, wrongly assumed that a new (nearly) single-phase compound was obtained, and performed indexing attempts; all of these resulted in erroneous conclusions. Considering the presence of BaBiO3, BaMoO4, and some intermediate/initial compounds, other results reported in Ref. [1] have no scientific value. We also would like to mention another paper by the same authors, where the preparation of “Sr3Bi2MoO9” was claimed [3]. However, no X-ray powder diffraction data or other experimental evidence were reported in Ref. [3] to support such a claim raising doubts in the existence of “Sr3Bi2MoO9”.No new experimental data were generated for this paper. Calculated X-ray powder diffraction patterns will be available on request.References[1] D. Panda, S. S. Hota, R. N. P. Choudhary, Development of a novel triple perovskite barium bismuth molybdate material for thermistor-based applications. Materials Science & Engineering B 296 (2023) 116616. doi: 10.1016/j.mseb.2023.116616[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] D. Panda, S. S. Hota, R. N. P. Choudhary, Development of a complex strontium bismuth molybdate material: Microstructural, electrical, and leakage current characteristics for storage and electronic device application. Mater. Res. Bull. 174 (2024) 112727. doi: 10.1016/j.materresbull.2024.112727  Figure 1. (a) An experimental X-ray powder diffraction pattern of a “Ba3Bi2MoO9” sample from Figure 1a of Ref. [1]. (b) Calculated X-ray diffraction patterns of BaCO3 (the green curve and the first row (from top) of green tick marks), BaMoO4 (the blue curve and the second row of blue tick marks), and BaBiO3 (the black curve and the third row of black tick marks for possible Bragg reflection positions). The calculated patterns (intensity ratios) were adjusted to match with the experimental X-ray powder diffraction pattern. Figure 1a is reproduced with the permission from Elsevier.4