Journal of Alloys and Compounds 863 (2021) 158500 
Contents lists available at ScienceDirect 
Journal of Alloys and Compounds 
journal homepage: www.elsevier.com/locate/jalcom 
Composition and temperature dependent structural investigation of the 
perovskite-type sodium-ion solid electrolyte series Na ]] 1/2−xLa1/2−xSr2xZrO3 ]]]]]]]] 
Frederick Z.T. Yanga, Vanessa K. Petersonb,c, Siegbert Schmida,⁎ 
a School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia 
b Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia 
c Institute for Superconducting and Electronic Materials, University of Wollongong, Squires Way, North Wollongong, NSW 2500, Australia    
a r t i c l e  i n f o   a b s t r a c t   
Article history: Owing to their vast chemical and structural flexibility, crystalline perovskite-type metal oxides (ABO3) are 
Received 14 September 2020 amongst the most promising solid electrolytes for use in all-solid-state batteries for large scale energy 
Received in revised form 21 December 2020 storage applications. The perovskite-type sodium-ion solid electrolyte series Na1/2-xLa1/2-xSr2xZrO3 have the 
Accepted 22 December 2020 highest reported ionic conductivities, and we re-examine their room temperature crystal structures using 
Available online 7 January 2021  
X-ray and high-resolution neutron powder diffraction. In contrast to a previous report, four members of the 
series, x = 1/16, 1/8, 1/6, and 1/4, were found to adopt orthorhombic symmetry with the space group Pbnm. 
Keywords: 
Solid-electrolyte Variable temperature neutron diffraction data (room temperature to 1100 °C) were used to probe tem-
All-solid-state batteries perature-dependent structural changes for the member of the series with the highest reported ionic con-
Na-ion battery ductivity (x = 1/6). A phase transition from orthorhombic Pbnm to tetragonal I4/mcm was identified at 
Perovskite-type 800 °C. 
Phase transition Crown Copyright © 2021 Published by Elsevier B.V. All rights reserved.    
1. Introduction the A-site and Ti4+ occupies the B-site. LLT showed high total ionic 
conductivity of 2 × 10−5 S cm−1 at room temperature, which was 
The development of high-performance sodium-ion batteries further increased by 50% through the introduction of Sr2+ onto the 
(SIBs) has recently attracted a lot of attention owing to the natural A-site [13]. This was due to an expansion in cell dimensions driven 
abundance of sodium resources [1,2]. This is particularly important by the larger ionic radius of Sr2+ (1.44 Å [14]) compared to Li+ and 
3+ 
for large scale energy storage, e.g. grid storage of sustainably sourced La (0.90 Å and 1.36 Å, respectively [14]), which improved the size 
+ 
energy or electric vehicles [3,4]. Current rechargeable battery tech- of the bottleneck in the diffusion pathway for Li ions. This system 
nologies’ reliance on highly flammable organic based liquid elec- has been extensively investigated with high ionic conductivity re-
trolytes presents major safety concerns, in particular for electric ported upon various A- and B-site cation substitutions [15,16]. In 
vehicles [5–7]. To address these safety issues, the organic liquid addition, concerted octahedral rotations in these systems have been 
electrolytes can be replaced by solid electrolytes to form all-solid- considered important for ionic conductivity [17,18]. 
state batteries (ASSBs). Solid electrolytes offer many advantages over Four members of the perovskite-type solid electrolyte system, 
organic electrolytes. As no liquid is used in ASSBs, their packing may Na1/2–xLa1/2–xSr2xZrO3 (NLSZ), a sodium analogue to LLT, were 
be simplified resulting in smaller size and increased energy density  recently synthesised and characterised by Zhao et al. [19]. The 
[8–11]. Importantly, the removal of highly flammable organic elec- structures of four representatives were reported to adopt cubic 
trolytes allows for the safe operation of the battery over larger symmetry with the space group P213. The assignment of this sym-
temperature ranges. metry was based on a wrong structure for SrZrO3, which has instead 
Perovskite-type oxides (ABO3) are among the most intensively been shown many times to adopt Pnma symmetry at room 
studied classes of solid electrolyte materials, owing to the flexibility temperature [20,21]. The cubic symmetry also appears highly unu-
and stability of this structure type. Inaguma et al. [12] synthesised sual since both theoretical end members of the series, i.e. SrZrO3 
and characterised Li La + 3+ 0.33 0.55TiO3 (LLT), where Li and La occupy (x = 0.5) and Na1/2La1/2ZrO3 (x = 0), adopt orthorhombic symmetry 
with Pnma space group [21,22]. There is no report in the literature of 
any substitutional perovskite solid solution where a member of the 
solid solution has a higher symmetry than both end members. 
⁎ Corresponding author. Amongst the investigated compositions, the x = 1/6 member of the 
E-mail address: siegbert.schmid@sydney.edu.au (S. Schmid). 
https://doi.org/10.1016/j.jallcom.2020.158500 
0925-8388/Crown Copyright © 2021 Published by Elsevier B.V. All rights reserved.   
F.Z.T. Yang, V.K. Peterson and S. Schmid Journal of Alloys and Compounds 863 (2021) 158500 
system, Na1/3La1/3Sr1/3ZrO3, was reported to have the highest ionic via conventional solid-state techniques and their structures 
conductivity of 1.025 × 10−5 S cm−1 at room temperature [19]. characterised using XRPD and NPD data. 
Given the very high sodium-ion conductivity of these phases and 
the scarcity and importance of such materials for future sodium-ion 3.1. X-ray powder diffraction 
batteries, a careful re-investigation of the structures is warranted, 
given the unusual symmetry previously published [19]. This manu- XRPD patterns of the samples collected at room temperature 
script reports the synthesis and renewed structural characterisation showed peak splitting as well as several very weak reflections, as can 
of the NLSZ solid electrolyte series at room temperature using both be seen in Fig. 1. It is evident that these weak reflections do not match 
X-ray and neutron powder diffraction data. In addition, structural the previous cubic model well (red peak markers) [19]. The combi-
changes for the member of the system with the highest reported nation of weak reflections and peak splitting, however, suggests the 
ionic conductivity, i.e. Na1/3La1/3Sr1/3ZrO3 (x = 1/6), are probed over a series adopts a lower symmetry than previously reported. Indeed, it 
wide range of temperatures using neutron powder diffraction. was possible to index the XRPD data for the four members of the 
series investigated here to an orthorhombic symmetry described by 
2. Experimental the same space group, Pbnm (note that Pbnm is an alternate setting for 
Pnma). This is therefore in agreement with the symmetry of both 
Members of the Na La Sr O system (x = 1/16, 1/8, 1/6, 1/4) theoretical end members, SrZrO3 and Na1/2La1/2ZrO3, as mentioned 1/2-x 1/2-x 2x 3 
were synthesised via solid-state reaction. Bulk amounts of starting above [21,22]. Hence, the presence of weak reflections between 
reagents Na2CO3 (Merk, 99.9%), SrCO3 (Aldrich 99.9%), and ZrO
~15 and ~24° 2θ is characteristic of the orthorhombic symmetry of a 
2 
(Aldrich 99%) were dried at 200 °C with the exception of La O perovskite-type structure, rather than impurity phases previously 2 3 
(Aithaca 99.98%), which was heated at 1000 °C for 15 h to remove reported (Figs. 1 and 2). 
any traces of moisture or carbon dioxide. Stoichiometric amounts of 
reagents were ground using a mortar and pestle, adding 10 wt% 
excess of Na2CO3 to compensate for possible sodium loss at high 
temperatures. The polycrystalline mixtures were annealed at 900 °C 
for 10 h, reground, and then pressed into ~5 cm rods using a hy-
drostatic press before being annealed at 1300 °C for a further 10 h. 
All samples were characterised using X-ray powder diffraction 
(XRPD) at Sydney Analytical. Samples were loaded into glass capil-
laries (0.5 mm diameter) and mounted on a spinning capillary stage. 
Data were collected on a STOE STADI P diffractometer using Mo-Kα1 
radiation (λ = 0.70932 Å) in Debye-Scherrer geometry over the range 
5° < 2θ < 55° with triple MYTHEN 1K detectors at room temperature 
(20-minute scans). 
All samples were further analysed using neutron powder dif-
fraction (NPD) at the Australian Centre for Neutron Scattering 
(ACNS) of the Australian Nuclear Science and Technology 
Organisation (ANSTO). NPD was carried out using the high-resolu-
tion neutron powder diffractometer Echidna [23] with the La11B6 Fig. 1. Diagnostic section of the XRPD patterns of the Na1/2−xLa1/2−xSr2xZrO3 series 
(NIST SRM 660b) standard reference material. All samples were showing signs of splitting (marked by #) and weak reflections (from x = 1/4 top to 1/ 
sealed in 9 mm vanadium cans and data collected using a neutron 16 bottom). The red peak markers indicate Bragg reflections expected for the cubic 
P2 3 perovskite model of Zhao et al. [19] and the green peak markers indicate the 
wavelength of 2.4394(5) Å from 5° < 2θ < 160° 2θ over a period of 5 h 1Bragg reflections consistent with the orthorhombic space group Pbnm. Data are offset 
at room temperature. in y for clarity. (For interpretation of the references to colour in this figure legend, the 
Variable temperature NPD data for Na1/3La1/3Sr1/3ZrO3 were ob- reader is referred to the web version of this article.) 
tained using the high intensity neutron powder diffractometer 
Wombat [24] from room temperature to 1100 °C. The sample was 
sealed in a 9 mm vanadium can and inserted into a 1600 °C ILL-type 
high-vacuum furnace. Data were collected using a neutron wave-
length of 2.4132(4) Å with the 331 reflection of a vertically focusing 
Ge monochromator at a heating rate of 5 °C per minute from room 
temperature to 400 °C and 1 °C per minute from 400 to 1100 °C with 
1 min scans per degree step during heating and cooling. 
Structural characterisation was performed with both XRPD and 
NPD data using the Rietveld method implemented in software 
package TOPAS Academic (v5) [25]. The background was fitted using 
a Chebyshev polynomial with eight terms. 
3. Results and discussion 
Members of the Na1/2-xLa1/2-xSr2xO3 system with x = 1/16, 1/8, 1/6, 
and 1/4, were previously reported with unusual cubic symmetry and Fig. 2. Rietveld refinement profile using XPRD data of Na1/3La1/3Sr1/3ZrO3. The ob-
high ionic conductivity, which reached 1.025 × 10−5 S cm−1 at room served pattern is marked by (o), the calculated pattern is shown by the red line and 
temperature for the x = 1/6 phase [19]. Owing to the enormous the difference between calculated and observed patterns is shown in blue. Bragg 
interest in such Na-ion conductors and the inherent connection positions for the orthorhombic Pbnm symmetry are indicated by the green tick marks. Rwp is the weighted profile R-factor. The black diamond marks an impurity reflection 
between ionic conductivity and symmetry, the structures of these assigned to ZrO2. (For interpretation of the references to colour in this figure legend, 
materials were re-investigated. The phases were synthesised the reader is referred to the web version of this article.) 
2 
F.Z.T. Yang, V.K. Peterson and S. Schmid Journal of Alloys and Compounds 863 (2021) 158500 
Table 1 
Unit cell parameters, in the pseudo-cubic setting, obtained from Rietveld refinement 
against XRPD data for Na1/2−xLa1/2−xSr2xZrO3, and the cubic unit cell parameters re-
ported by Zhao et al. [19].        
x a (Å) b (Å) c (Å) Volume (Å3) Zhao et al. (Å)  
1/16 4.08944(4) 4.07775(4) 4.06179(4) 67.73325(2) 4.07056 
1/8 4.09045(4) 4.07931(4) 4.06115(4) 67.76522(2) 4.07675 
1/6 4.08977(4) 4.08188(4) 4.06491(4) 67.85941(2) 4.08145 
1/4 4.09367(4) 4.08587(4) 4.07075(4) 68.08819(2) 4.08841    
In particular, the weak reflection at ~16.5° 2θ corresponds to the 
reflection at ~36° 2θ in Zhao et al.’s Fig. 2a. There it is identified as a 
La2Zr2O7 reflection. That reflection, however, would appear at ~33° 
2θ, should be lower in intensity than the reflection at ~29° 2θ and 
Fig. 3. Rietveld refinement profile using NPD data of Na La Sr ZrO . The ob-
these two reflections should not change relative intensity across 1/4 1/4 1/2 3served pattern is marked by (o), the calculated pattern shown in red and the differ-
the four patterns. Na, La, and Sr share the A-site in the centre of the ence between calculated and observed patterns is shown in blue. Bragg positions for 
unit cell, while Zr occupies the B-site on the corners of the unit cell. the orthorhombic Pbnm symmetry are indicated by the green tick marks. The inset 
◦ 
The orthorhombic symmetry has two crystallographically in- from 50 < 2θ < 70
◦ highlights the superlattice reflections that are characteristic of 
octahedral tilting within a perovskite-type structure. Rwp is the weighted profile R- dependent oxygen sites that form the octahedron around the B-site factor. (For interpretation of the references to colour in this figure legend, the reader is 
cation. The Zr‒O distances are ~2.09 Å to O1 (x2) and ~2.09 Å to referred to the web version of this article.) 
O2 (x4), confirming that the octahedra are almost regular (see  
Table S1). 
It is evident that as Na+ and La3+ ions were substituted by Sr2+, the Table 2 
diffraction peaks shifted towards lower 2θ angles (Fig. 1). This shift Space group and refined atomic parameters for Na1/2−xLa1/2−xSr2xZrO3 using Echidna 
2+ + data collected at room temperature. Figures of merit are the Bragg R-factor R and indicates an expansion of the unit cell as Sr is substituted for Na Bragg the reduced chi-squared χ2.       
and La3+ on the A-site. This is expected given the relative differences 
in effective ionic radii (Na+ = 1.39 Å, La3+ = 1.36 Å, Sr2+ = 1.44 Å, all Sample (x) 1/16 1/8 1/6 1/4 
Space Group Pbnm Pbnm Pbnm Pbnm 
three in 12-fold coordination [14]), and is consistent with trends re-
ported for perovskite-type Li-ion solid electrolytes [13]. The unit cell Na/La/Srx -0.00449 (3) -0.00396 (3) -0.00408 (3) -0.00680 (4) 
parameters of the orthorhombic Pbnm perovskite can be described in Na/La/Sry 0.48161 (3) 0.47745 (4) 0.47429 (4) 0.47494 (4) 
terms of the ideal cubic perovskite given by a ~ 2 a , b ~ 2 a and Na/La/Srz 0.25 0.25 0.25 0.25 p p,
c ~ 2ap, where ap is the length of an ideal cubic perovskite unit cell. 
Biso 1.12853(1) 1.27822(1) 1.03462(1) 0.75763(2) 
Zrx 0 0 0 0 
Unit cell parameters obtained from Rietveld refinement for each Zry 0 0 0 0 
member of the series were converted to the pseudo-cubic values for Zrz 0 0 0 0 
ease of comparison with those reported by Zhao et al. [19] (Table 1). Biso 0.35313(2) 0.51755(1) 0.23168(2) 0.29730(2) 
The unit cell volume increases with increasing Sr2+ substitution O1x 0.07872(3) 0.07746(3) 0.07790(3) 0.07317(4) 
O1y 0.01513(3) 0.01534(4) 0.01734(4) 0.01598(4) 
O1z 0.25 0.25 0.25 0.25 
Biso 0.27249(1) 0.75695(1) 0.67026(1) 0.38328(2) 
3.2. Neutron powder diffraction O2x 0.21113(4) 0.21065(4) 0.20997(4) 0.21176(4) 
O2y 0.28895(4) 0.28882(4) 0.29023(5) 0.28700(4) 
The weak superstructure reflections observed in the XRPD data O2z -0.03964(4) -0.03867(4) -0.03779(3) -0.03690(4) 
Biso 0.92204(1) 0.99471(1) 0.85226(2) 0.77680(2) 
are due to tilting of octahedra, which cause the oxygen atoms to RBragg (%) 5.58 4.27 4.08 2.02 
move from their high-symmetry positions. For a detailed analysis of χ2 6.89 7.05 7.20 3.21 
the octahedral tilting within the perovskite structure, NPD data were 
used owing to the relatively larger scattering from oxygen compared 
to the heavier metal atoms. High-resolution NPD data collected at 3.2.1. Variable temperature structural characterisation 
room temperature on Echidna for all members of the series showed Variable temperature NPD data were collected for the member of 
the presence of R-point and M-point superlattice reflections, with the Na1/2-xLa1/2-xSr2xZrO3 series with the highest ionic-conductivity, 
h, k, l = odd, odd, even, and odd, even, even, indices in the pseudo- x = 1/6 (Na1/3La1/3Sr1/3ZrO3) as previously reported [19], using the 
cubic double-perovskite setting, respectively, indicative of the pre- Wombat diffractometer from ambient temperature to 1100 ◦C. Re-
sence of both in- and out-of-phase tilting of the BO6 octahedra. The flections in the diffraction patterns were found to shift towards 
combination of both tilts within the structure resulted in the ap- lower 2θ angles on heating, indicating expansion of the unit cell with 
pearance of additional X-point reflections (Fig. 3). Using Rietveld increasing temperature (Fig. 5). 
refinement against the NPD patterns for all four members of the The integrated intensities of the M- and R-point super lattice re-
series confirmed the orthorhombic symmetry described by the space flections at ~56◦ and ~59◦, respectively, were extracted from sequential 
group Pbnm, consistent with XPRD data analysis (Table 2). All single-peak analysis using TOPAS Academic (v5). The peak shape was 
members of the series were found to have out-of-phase tilting of the modelled using a pseudo-Voigt function. For the orthorhombic Pbnm 
BO6 octahedra about the [100]p and [010]p axes with an in-phase tilt phase, the integrated intensity of the M-point with hkl indices 120 and 
along the [001]p axis of the pseudo-cubic perovskite (Fig. 4), denoted 210, denoted by I(120 + 210)Pbnm, continuously decreased with in-
in Glazer’s notation as a- a- c+ [26]. The Goldschmidt tolerance factor creasing temperature. The intensity of I(120 + 210)Pbnm represents the 
was calculated to be 0.937, consistent with the tilts observed in this amplitude of the in-phase tilting of successive layers about the [001]p 
perovskite system [27]. Due to the mixed nature of the A-site, the axis of the pseudo-cubic perovskite. This corresponds to the M3 point of 
mean ionic radius of Na+, La3+, and Sr2+ was used to calculate the the cubic Brillouin zone [28]. This peak was undetectable from 800 °C 
tolerance factor. (Fig. 6a), consistent with an orthorhombic Pbnm to tetragonal I4/mcm 
phase transition. Integrated intensities of the R-point with hkl indices 
3 
F.Z.T. Yang, V.K. Peterson and S. Schmid Journal of Alloys and Compounds 863 (2021) 158500 
Fig. 4. Representation of octahedral tilting within the orthorhombic Pbnm space group. BO6 octahedra are blue, B-site metal position green and O atoms are red. (a) and (b) 
represent out-of-phase tilting along the [100]p and [010]p axes and (c) represents in-phase tilting along the [001]p axis with respect to the pseudo-cubic perovskite. (For in-
terpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 
R-point peak intensities I(121 + 211 + 103)Pbnm are now represented as I 
(211)I4/mcm as the structure undergoes a first order transition from or-
thorhombic Pbnm to tetragonal I4/mcm (Fig. 6b). No additional transi-
tions were found between 800 and 1100 °C, as reflected by the 
continuing presence of the R-point reflection. This is consistent with 
the previously reported high temperature Pbnm – I4/mcm transitions in 
perovskite structures [20,29,31]. 
Sequential Rietveld refinements were performed against the 
variable temperature Wombat data from room temperature to 800 ◦C 
in the orthorhombic space group Pbnm. Against data from 800 to 
1100 °C, structural models were refined in the space group I4/mcm 
(a0 a0 c-) with a single out-of-phase tilt along the [001]p axis (Fig. 7). 
In the high-temperature I4/mcm phase Na, La, and Sr occupy the 
A-site position in the centre of the unit cell, while Zr occupies the 
corners (Table 3). There are still two crystallographically in-
dependent oxygen sites in the structure, however, O1 now has no 
refinable positional parameters while O2 has only 1 instead 2. The 
Zr‒O distances are ~2.06 Å to O1 (x2) and ~2.09 Å to O2 (x4), 
confirming that the octahedra are slightly squashed along the 
c-direction (see Table S2). 
Fig. 5. Variable temperature NPD data for Na La Sr ZrO from Wombat between 4. Conclusion 1/3 1/3 1/3 3 
room temperature and 1100 °C using λ = 2.4132(4) Å neutrons. Intensity ranges from 
lowest (blue) to highest (red) and highlights the decrease in intensity of the M- and R- The perovskite-type sodium-ion solid electrolyte series 
point superlattice reflection with increasing temperature. (For interpretation of the Na1/2-xLa1/2-xSr2xZrO3 (x = 1/16, 1/8, 1/6, 1/4) was synthesised using 
references to colour in this figure legend, the reader is referred to the web version of 
this article.) solid-state techniques and the structures successfully determined. 
Using X-ray and neutron powder diffraction data collected at room 
temperature, all four investigated members of the series were found 
121, 211, and 103 denoted by I(121 + 211 + 103)Pbnm also decreased with to have orthorhombic symmetry described by the space group Pbnm 
increasing temperature (Fig. 6b). The intensity I(121 + 211 + 103)Pbnm is (a- a- c+). This is in contrast to the previous conclusion by Zhao et al.  
related to the amplitude of the out-of-phase tilting of the BO6 octa- [19] that this perovskite system adopts cubic P213 space-group 
hedra about the [100]p and [010]p direction of the pseudo-cubic per- symmetry. Our result is consistent with the structures for the the-
ovskite [20,29,30]. This corresponds to the R25 point of the cubic oretical endmembers x = 0 and x = 0.5, i.e. Na1/2La1/2ZrO3 and SrZrO3  
Brillouin zone, and can also be described as a single out-of-phase tilt [21,22], respectively, also adopting Pbnm space-group symmetry, and 
about the [110]p axis of the octahedron [28]. For the transition at with group theoretical considerations [28]. The progressive re-
800 °C, according to the group theoretical analysis by Howard and placement of Na+ and La3+ with the larger Sr2+ cation on the A-site 
Stokes [28], three space groups are possible with out-of-phase tilting resulted in an increase of the unit cell parameters. 
only, R3c (a- a- a-), Imma (a0 b- b-), or I4/mcm (a0 a0 c-). The x = 0.5 In addition, a structural phase transition was found for the x = 1/6 
theoretical end member SrZrO3 was found by Howard et al. [20] to member of the series (Na1/3La1/3Sr1/3ZrO3) using variable tempera-
have phase transitions from room temperature to 1230 °C of Pnma → ture neutron powder diffraction data collected from room tem-
Imma → I4/mcm → Pm3m. The continuity in the decrease of the R-point perature to 1100 °C. Through the analysis of integrated intensities, 
intensity suggests the structure might undergo a second order con- the structure of Na1/3La1/3Sr1/3ZrO3 was found to undergo a phase 
tinuous transition to Imma, i.e. following the high temperature phase transition from orthorhombic Pbnm (a- a- c+) to tetragonal I4/mcm 
transitions of SrZrO3. As both the Imma and I4/mcm space groups have (a0 a0 c-) at 800 °C. 
the same characteristic R-point reflections, the difference between the The accurate structure determination for this solid-electrolyte 
space groups was reported to be the splitting of the 002p diffraction system will allow for a better understanding of the structure ─ 
peak for SrZrO3 [20]. However, no splitting was observed for the 002p property relationship and targeted improvements through chemical 
diffraction peak in Na1/3La1/3Sr1/3ZrO3 around 800 °C. Hence, the and structural modifications. 
4 
F.Z.T. Yang, V.K. Peterson and S. Schmid Journal of Alloys and Compounds 863 (2021) 158500 
Fig. 6. Temperature dependence of integrated intensities of Na1/3La1/3Sr1/3ZrO3 reflections obtained from single peak fitting. (a) Orthorhombic M-point 120 and 210 reflections, I 
(120 + 210)Pbnm. (b) Orthorhombic R-point 121, 103, and 210 reflections, I(121 + 103 + 211)Pbnm as well as the tetragonal 211 reflection, I(211)I4/mcm. 
Fig. 7. Representation of the change in direction for the out-of-phase tilt from [100]p and [010]p axes to the [001]p axis for a first order discontinuous transition from Pbnm to I4/ 
mcm space group symmetry, representing the tilt system a0 a0 c-. BO6 octahedra are blue and O atoms are red. (For interpretation of the references to colour in this figure legend, 
the reader is referred to the web version of this article.) 
Table 3 CRediT authorship contribution statement 
Space group and refined atomic positions for Na1/3La1/3 
Sr1/3O3 from Wombat data collected at 850 °C.    The manuscript was written based on contributions from all 
Space group I4/mcm  authors. 
Na/La/Srx 0 
Na/La/Sry 0.5 
Na/La/Sr 0.25 Declaration of Competing Interest z 
Biso [Å2] 1.69081(1) 
Zrx 0 The authors declare that they have no known competing fi-
Zry 0 nancial interests or personal relationships that could have appeared 
Zrz 0 
B [Å2
to influence the work reported in this paper. 
iso ] 0.91370(1) 
O1x 0 
O1y 0 
O1z 0.25 
Acknowledgments 
B 2iso [Å ] 3.46111(1) 
O2x 0.29799 (3) We acknowledge and pay respect to the Gadigal people of the 
O2y 0.79799 Eora Nation, the traditional owners of the land on which this re-
O2z 0 
2 search was conducted. We thank Sydney Analytical, a core research Biso [Å ] 3.77866 (1) 
R [%] 5.96 facility at the University of Sydney, for help with characterisation of Bragg 
χ2 4.02    samples and financial support. Neutron powder diffraction data 
were collected at the Australian Centre for Neutron Scattering 
5 
F.Z.T. Yang, V.K. Peterson and S. Schmid Journal of Alloys and Compounds 863 (2021) 158500 
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