List of Figures
xxv
tie-lines while red dashed lines are tie-lines at the outer edges of
the three-phase regions. The blue dotted line represents a phase
transition from the cubic rocksalt to the layered rocksalt
structures. b The phase diagram for samples heated in flowing
oxygen obtained by regular cooling from 800
◦ C ...................
62
Fig. 5.3
A partial phase diagram obtained in air with regular cooling.
Regions showing severe lithium loss were avoided. Filled points
represent single-phase samples while empty points show
coexistence of multiple phases ........................................
63
Fig. 5.4
The Gibbs triangle with labels used throughout this chapter.......
63
Fig. 5.5
X-ray diffraction (XRD) patterns of a few single-phase spinel
structures. Samples E 5 and F 5 are labeled in Fig. 5.4. The
database peaks shown are for spinel NiMn 2 O 4 , from JCPDS
#84-0542. For clarity, only every third data point is shown........
64
Fig. 5.6
X-ray diffraction (XRD) patterns obtained for single-phase spinel
structures. Points E 5 and F 5 are labeled in Fig. 5.4 (left). XRD
patterns near the boundary of the spinel region; the blue arrow
matches that shown in Fig. 5.4 and indicates the position of the
layered (104) peak here. The other peak is the spinel (400) (right)
64
Fig. 5.7
Contour plots of the lattice parameter in the cubic spinel region.
Filled points indicate single-phase samples while open symbols
are used to denote coexistence of multiple phases. The green
dashed line represents the stoichiometric spinel composition line:
LiNi x Mn 2−x O 4 ; x ≤ 0.5 ...............................................
65
Fig. 5.8
Stack of X-ray diffraction (XRD) patterns for single-phase
structures obtained by regular cooling in oxygen (left panel). The
same scans lines in the left panel are for Ni 6 MnO 8 from JCPDS
reference # 89-4619. C 5 and D 5 refer to compositions defined in
Fig. 5.4 ...................................................................
67
Fig. 5.9
The c/a lattice parameter ratio as a function of Li fraction for
three different manganese fractions obtained by regular cooling
in oxygen and fitting the X-ray diffraction (XRD) patterns as
hexagonal structures ....................................................
68
Fig. 5.10 Contour plots of the cubic lattice parameter in the rocksalt region.
Open symbols show phase separation while the closed symbols
represent single-phase samples........................................
69
Fig. 5.11 Ordered rocksalt phases obtained in oxygen along the line
Li = 0.2. Ordering is more pronounced in the slower cooled
samples. The expected peaks for Ni 6 MnO 8 (JCPDS #89-4619)
are shown as vertical lines. The coordinates are (Li, Mn)..........
71
Fig. 5.12 A comparison of the angles α and α c obtained for a point X,
(0.30, 0.66). The spinel lattice parameter at point X was 8.225 ±
0.003 Å such that extrapolation between lattice parameters along
the boundary defines point X c (left). α c as a function of α for
samples throughout the coexistence region. The line,
α c = 1.03α − 1.2 is a linear fit to the data (right) .................
72
xxv
tie-lines while red dashed lines are tie-lines at the outer edges of
the three-phase regions. The blue dotted line represents a phase
transition from the cubic rocksalt to the layered rocksalt
structures. b The phase diagram for samples heated in flowing
oxygen obtained by regular cooling from 800
◦ C ...................
62
Fig. 5.3
A partial phase diagram obtained in air with regular cooling.
Regions showing severe lithium loss were avoided. Filled points
represent single-phase samples while empty points show
coexistence of multiple phases ........................................
63
Fig. 5.4
The Gibbs triangle with labels used throughout this chapter.......
63
Fig. 5.5
X-ray diffraction (XRD) patterns of a few single-phase spinel
structures. Samples E 5 and F 5 are labeled in Fig. 5.4. The
database peaks shown are for spinel NiMn 2 O 4 , from JCPDS
#84-0542. For clarity, only every third data point is shown........
64
Fig. 5.6
X-ray diffraction (XRD) patterns obtained for single-phase spinel
structures. Points E 5 and F 5 are labeled in Fig. 5.4 (left). XRD
patterns near the boundary of the spinel region; the blue arrow
matches that shown in Fig. 5.4 and indicates the position of the
layered (104) peak here. The other peak is the spinel (400) (right)
64
Fig. 5.7
Contour plots of the lattice parameter in the cubic spinel region.
Filled points indicate single-phase samples while open symbols
are used to denote coexistence of multiple phases. The green
dashed line represents the stoichiometric spinel composition line:
LiNi x Mn 2−x O 4 ; x ≤ 0.5 ...............................................
65
Fig. 5.8
Stack of X-ray diffraction (XRD) patterns for single-phase
structures obtained by regular cooling in oxygen (left panel). The
same scans lines in the left panel are for Ni 6 MnO 8 from JCPDS
reference # 89-4619. C 5 and D 5 refer to compositions defined in
Fig. 5.4 ...................................................................
67
Fig. 5.9
The c/a lattice parameter ratio as a function of Li fraction for
three different manganese fractions obtained by regular cooling
in oxygen and fitting the X-ray diffraction (XRD) patterns as
hexagonal structures ....................................................
68
Fig. 5.10 Contour plots of the cubic lattice parameter in the rocksalt region.
Open symbols show phase separation while the closed symbols
represent single-phase samples........................................
69
Fig. 5.11 Ordered rocksalt phases obtained in oxygen along the line
Li = 0.2. Ordering is more pronounced in the slower cooled
samples. The expected peaks for Ni 6 MnO 8 (JCPDS #89-4619)
are shown as vertical lines. The coordinates are (Li, Mn)..........
71
Fig. 5.12 A comparison of the angles α and α c obtained for a point X,
(0.30, 0.66). The spinel lattice parameter at point X was 8.225 ±
0.003 Å such that extrapolation between lattice parameters along
the boundary defines point X c (left). α c as a function of α for
samples throughout the coexistence region. The line,
α c = 1.03α − 1.2 is a linear fit to the data (right) .................
72