Supplemental Materials



Crystal chemistry and ion-irradiation resistance of Ln2ZrO5 compounds with Ln = Sm, Eu, Gd and Tb


Robert D. Aughterson, Gregory R. Lumpkin, Zhaoming Zhang, Maxim Avdeev, Linggen Kong


Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW Australia



















Figure S1 shows SEM backscattered images of Nd2ZrO5 and Dy2ZrO5 materials. Close inspection of these images reveals a secondary phase, sub-micron domains, appearing as lighter grey contrast. A higher magnification was used for the image in Figure S1-b to aid with distinguishing these sub-micron domains. Due to the small size of these secondary phase domains quantitative analysis via SEM energy dispersive X-ray spectroscopy was not possible. At a qualitative level the secondary phase was richer in the lanthanide relative to zirconium, whilst the matrix had a lower Ln:Zr ratio than the target 2:1. This would indicate limited solubility in the solid solution between Ln2ZrO5 to Ln2Zr2O7. Previous studies have found this to be the case for the Nd2O3–ZrO2 system where two cubic phases are found around the 50 mol% Nd2O3 phase region.S1 In a previous study on the pseudo-binary Dy2O3–ZrO2 system it was found that sintering at 1150 °C gave a multi-phase material for 50 mol % Dy2O3 / 50mol % ZrO2 (i.e., nominally Dy2ZrO5), whilst sintering at 1450 °C for 16 days was sufficient to fabricate Dy2ZrO5 in single phase form with cubic, fluorite symmetry.S2 This previous study used X-ray diffraction for structure and phase analysis so it may be possible that the presence of a secondary phase with subtly different cation ratio may have been missed. These subtle variations in cation ratio were relatively easily identified in our study using the back-scattered imaging approach (Figure S1). It is also possible that the lower sintering temperature, 1400 °C, and shorter sintering time, 24 h, used in our study was insufficient to facilitate the complete conversion of precursors to the target Dy2ZrO5 single phase material. However, the fabrication of other single phase Ln2ZrO5 materials at 1400 °C for 24 h sintering highlights the improved reaction kinetics achieved for some zirconates via the wet-chemistry approach applied in this study.
    A phase relationship diagram based on multiple 1600 °C sintering in air for 5 plus 2–3 days developed by Withers et alS3 included various Ln2ZrO5 compounds and further confirmed that the targeting Nd2ZrO5 resulted in multi-phase, and also established Dy2ZrO5 as a single phase with cubic type structure using XRD and TEM characterization. The phase relation study of Dy2O3–ZrO2 by Pascual and DuranS2 established a transition from multi-crystal structure to single fluorite phase for Dy2ZrO5 occurred at or above 1450 °C, however the precursors were initially either sintered above 1800 °C or melted to ensure complete reaction.



FIGURE S1 SEM annular selective backscattered images for the multi-phase, mixed stoichiometry, compounds fabricated (a) Nd2ZrO5, and (b) Dy2ZrO5. Black regions are pores. Submicron domains of secondary phase appear as variation in grey contrast. Figure (b) is at higher magnification to aid in highlighting the secondary phase. Porosity measurement on SEM back-scattered images using ImageJ software.



FIGURE S2 SEM backscattered images of (a) Sm2ZrO5 fabricated via wet-chemistry route, (b) image contrast adjusted via threshold in preparation for image analysis of porosity.



FIGURE S3 SEM backscattered images of (a) Sm2ZrO5 fabricated via conventional mixed oxide route, (b) image contrast adjusted via threshold in preparation for image analysis of porosity.

TEM-EDS analyses

The cation errors are based on two standard deviations. The number of anions, oxygen, is calculated based on cation ratios and their expected oxidation states, Ln3+ and Zr4+. The TEM EDS system was calibrated with numerous titanate based standards including pyrochlores and zirconolites.

TABLE S1 The TEM–EDS analyses of Sm2ZrO5 compound.
	Sm2ZrO5 
	Atomic %

	Spectrum
	Zr
	Sm
	O

	1
	12.25
	25.3
	62.45

	2
	12.47
	25.04
	62.49

	3
	12.51
	24.99
	62.5

	4
	11.94
	25.67
	62.39

	5
	12.32
	25.22
	62.46

	6
	12.56
	24.93
	62.51

	7
	12.56
	24.92
	62.51

	8
	12.19
	25.37
	62.44

	9
	12.47
	25.04
	62.49

	10
	12.62
	24.86
	62.52

	11
	11.84
	25.79
	62.37

	12
	12.28
	25.26
	62.46

	13
	12.74
	24.71
	62.55

	14
	11.81
	25.83
	62.36

	15
	12.45
	25.06
	62.49

	16
	11.78
	25.86
	62.36

	17
	12.64
	24.83
	62.53

	18
	11.92
	25.7
	62.38

	19
	11.51
	26.19
	62.3

	20
	12.71
	24.75
	62.54

	21
	12.58
	24.9
	62.52

	22
	12.34
	25.19
	62.47

	23
	11.55
	26.14
	62.31

	24
	12.42
	25.1
	62.48

	25
	12.03
	25.56
	62.41

	26
	13.33
	24.01
	62.67

	27
	11.67
	26
	62.33

	28
	12.42
	25.09
	62.48

	29
	12.21
	25.35
	62.44

	30
	11.85
	25.77
	62.37

	
	
	
	

	Average
	12.27
	25.28
	62.45

	Maximum
	13.33
	26.19
	62.67

	Minimum
	11.51
	24.01
	62.30

	Standard deviation
	0.40
	0.48
	0.08

	
	
	
	

	Average cation - anion
	0.97
	2.00
	4.94

	plus or minus
	0.06
	0.08
	0.01




TABLE S2 The TEM–EDS analyses of Eu2ZrO5 compound.
	Eu2ZrO5 
	Atomic %

	Spectrum
	Zr
	Eu
	O

	1
	11.67
	25.99
	62.33

	2
	12.19
	25.38
	62.44

	3
	11.95
	25.66
	62.39

	4
	11.57
	26.11
	62.31

	5
	12.5
	25
	62.5

	6
	11.71
	25.95
	62.34

	7
	11.84
	25.8
	62.37

	8
	11.89
	25.73
	62.38

	9
	11.72
	25.93
	62.34

	10
	11.91
	25.70
	62.38

	11
	11.85
	25.78
	62.37

	12
	11.81
	25.83
	62.36

	13
	12.24
	25.32
	62.45

	14
	11.77
	25.87
	62.35

	15
	12.59
	24.89
	62.52

	16
	11.76
	25.89
	62.35

	17
	11.83
	25.8
	62.37

	18
	11.89
	25.73
	62.38

	19
	11.98
	25.62
	62.4

	20
	11.79
	25.85
	62.36

	21
	11.86
	25.76
	62.37

	22
	11.72
	25.93
	62.34

	23
	11.86
	25.77
	62.37

	24
	11.99
	25.61
	62.4

	25
	11.74
	25.91
	62.35

	26
	11.94
	25.67
	62.39

	27
	12.22
	25.33
	62.44

	28
	11.88
	25.74
	62.38

	29
	12.32
	25.21
	62.46

	30
	12.08
	25.5
	62.42

	
	
	
	

	Average
	11.94
	25.68
	62.39

	Maximum
	12.59
	26.11
	62.52

	Minimum
	11.57
	24.89
	62.31

	Standard deviation
	0.24
	0.28
	0.05

	
	
	
	

	Average cation - anion
	0.93
	2.00
	4.86

	plus or minus
	0.04
	0.04
	0.01





TABLE S3 The TEM–EDS analyses of Gd2ZrO5 compound.
	Gd2ZrO5 
	Atomic %

	Spectrum
	Zr
	Gd
	O

	1
	11.73
	25.92
	62.35

	2
	11.77
	25.88
	62.35

	3
	12.13
	25.44
	62.43

	4
	11.81
	25.83
	62.36

	5
	11.88
	25.74
	62.38

	6
	11.87
	25.76
	62.37

	7
	11.93
	25.68
	62.39

	8
	12.08
	25.50
	62.42

	9
	11.84
	25.79
	62.37

	10
	11.77
	25.87
	62.35

	11
	11.83
	25.81
	62.37

	12
	11.73
	25.92
	62.35

	13
	11.82
	25.82
	62.36

	14
	11.83
	25.81
	62.37

	15
	12.25
	25.3
	62.45

	16
	11.64
	26.04
	62.33

	17
	12.08
	25.5
	62.42

	18
	11.63
	26.04
	62.33

	19
	13.12
	24.26
	62.62

	20
	11.76
	25.89
	62.35

	21
	11.95
	25.66
	62.39

	22
	11.75
	25.9
	62.35

	23
	11.92
	25.7
	62.38

	24
	11.77
	25.88
	62.35

	25
	11.87
	25.76
	62.37

	26
	11.82
	25.82
	62.36

	27
	11.67
	26
	62.33

	28
	10.85
	26.97
	62.17

	29
	11.74
	25.91
	62.35

	30
	11.86
	25.77
	62.37

	
	
	
	

	Average
	11.86
	25.77
	62.37

	Maximum
	13.12
	26.97
	62.62

	Minimum
	10.85
	24.26
	62.17

	Standard deviation
	0.33
	0.39
	0.06

	
	
	
	

	Average cation - anion
	0.92
	2.00
	4.84

	plus or minus
	0.05
	0.06
	0.01




TABLE S4 The TEM–EDS analyses of Tb2ZrO5 compound.
	Tb2ZrO5 
	Atomic %

	Spectrum
	Zr
	Tb
	O

	1
	12.62
	24.85
	62.52

	2
	12.9
	24.52
	62.58

	3
	12.77
	24.68
	62.55

	4
	12.87
	24.55
	62.57

	5
	12.52
	24.98
	62.5

	6
	13.09
	24.29
	62.62

	7
	13.17
	24.20
	62.63

	8
	12.51
	24.98
	62.5

	9
	12.89
	24.54
	62.58

	10
	13.89
	23.33
	62.78

	11
	13.55
	23.74
	62.71

	12
	12.84
	24.59
	62.57

	13
	13.03
	24.36
	62.61

	14
	12.45
	25.06
	62.49

	15
	12.78
	24.66
	62.56

	16
	12.9
	24.52
	62.58

	17
	12.86
	24.57
	62.57

	18
	12.11
	25.46
	62.42

	19
	13.07
	24.31
	62.61

	20
	12.82
	24.62
	62.56

	21
	12.68
	24.78
	62.54

	22
	12.93
	24.49
	62.59

	23
	12.63
	24.84
	62.53

	24
	12.86
	24.57
	62.57

	25
	13.17
	24.2
	62.63

	26
	13.5
	23.8
	62.7

	27
	12.32
	25.22
	62.46

	28
	12.77
	24.68
	62.55

	29
	12.81
	24.63
	62.56

	30
	12.88
	24.55
	62.58

	
	
	
	

	Average
	12.87
	24.55
	62.57

	Maximum
	13.89
	25.46
	62.78

	Minimum
	12.11
	23.33
	62.42

	Standard deviation
	0.35
	0.42
	0.07

	
	
	
	

	Average cation - anion
	1.05
	2.00
	5.10

	plus or minus
	0.06
	0.07
	0.01




References
S1. 	Ohtani H, Matsumoto S, Sundman B, Sakuma T, Hasebe M. Equilibrium between fluorite and pyrochlore structures in the ZrO2–Nd2O3 system. J Mater Trans. 2005;46:1167–1174.
S2.	Pascual C, Duran P. Phase relations and ordering in the dysprosia-zirconia system. J Mater Sci. 1980;15:1701–1708.
S3.	Withers RL, Thompson JG, Barlow PJ. An electron, and X-ray powder, diffraction study of cubic, fluorite-related phases in various ZrO2–Ln2O3 systems. J Solid State Chem. 1991;94:89–105.
2

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