## 3 Results and Discussion
### In-Situ XRD Studies of the Electrode Materials
According to the dilatometric data, a transition in the linear thermal expansion coefficient values from 5.6-7.1 to 11.4-14.8 \(\times\) 10\({}^{-6}\) K\({}^{-1}\) was observed at approximately 400 \({}^{\circ}\)C in air. The difference between the data on thermal expansion obtained by different methods is caused by the anisotropy of the layered R-P structure [28]. Figure 5 shows the concentration dependencies of the lattice parameters and the unit cell volume for all the samples after the treatment in the different gas atmospheres. The general trend is the same: the \(a\) and \(b\) parameters gradually decrease with increasing copper content; the \(c\) parameter and the unit cell volume steadily increase for the samples with low copper content (for the NCNCO01 and NCNCO2 samples) and then sharply increase for the NCNCO03 and NCNCO04 samples. The difference between the same lattice parameters after the treatment in different gas atmospheres reflects a change in the oxygen stoichiometry and/or in the structure, namely, the re-distribution of oxygen, as was shown by NPD. A representative value in this sense is an orthorhombic distortion (Table 4), which shows a degree of the difference between the \(a\) and \(b\) parameters. Regarding this, from the point of decreasing the strain in the structure, orthorhombic distortion is lower in the presence of the interstitial oxygen (the NCNCO00-NCNCO02 samples after the \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \multirow{3}{*}{**Sample**} & **UCP (Å)** & **UCP (Å)** & **Orthorhombic** & **T\({}_{pl}\) (\({}^{\circ}\)C)** & **T\({}_{pl}\) (\({}^{\circ}\)C)** & **VTEC** & \(\times\)10\({}^{-6}\) (K\({}^{-1}\)) & \(\times\)10\({}^{-6}\) (K\({}^{-1}\)) \\  & **UCV (Å)** & **UCV (Å)** & **Distortion 1** & **Air Flow** & **He Flow** & **Air Flow** & **Air Flow** & **He Flow** \\  & **after Treatment** & **after Treatment** & **after Synthetic** & **Heating/** & **Heating/** & **Bmab** sp.gr/ & _Bmab_ sp.gr/ \\  & **in Synthetic Air** & **in He Flow** & **Air/ after He** & **Coiling** & **Coiling** & **I4/mmm** sp.gr & _I4/mmm_ & **sp.gr** \\ \hline \multirow{4}{*}{NCNCO00} & \(a\) = 5.3253 (1) & \(a\) = 5.3191 (1) & \multirow{4}{*}{1.13/1.53} & \multirow{4}{*}{430/375} & \multirow{4}{*}{385/485} & \multirow{4}{*}{9.0/11.7} & \multirow{4}{*}{9.3/12.0} \\  & \(b\) = 5.3862 (1) & \(b\) = 5.4018 (1) & & & & & \\  & \(c\) = 12.2690 (2) & \(c\) = 12.2558 (2) & & & & & \\  & \(V\) = 351.916 (7) & \(V\) = 352.144 (7) & & & & & \\  & \(a\) = 5.3172 (2) & \(a\) = 5.3118 (1) & & & & & \\  & \(b\) = 5.3840 (2) & \(b\) = 5.3956 (1) & 1.24/1.56 & 410/365 & 365/440 & 7.8/9.1 & 8.2/9.2 \\  & \(c\) = 12.3121 (5) & \(c\) = 12.3009 (2) & & & & & \\  & \(V\) = 352.47 (2) & \(V\) = 352.56 (2) & & & & & \\  & \(a\) = 5.3070 (2) & \(a\) = 5.3042 (2) & & & & & \\  & \(b\) = 5.3789 (2) & \(b\) = 5.3901 (2) & 1.34/1.59 & 420/400 & 430/445 & 8.7/10.0 & 8.0/10.4 \\  & \(c\) = 12.3600 (4) & \(c\) = 12.3475 (3) & & & & & \\  & \(V\) = 352.83 (1) & \(V\) = 353.01 (2) & & & & & \\  & \(a\) = 5.2974 (3) & \(a\) = 5.2971 (2) & & & & & \\  & \(b\) = 5.3757 (3) & \(b\) = 5.3778 (2) & 1.46/1.50 & 400–500/ & 400–500/ & n/a & n/a \\  & \(c\) = 12.4470 (7) & \(c\) = 12.4341 (4) & & & & & \\  & \(V\) = 354.46 (6) & \(V\) = 352.41 (3) & & & & & \\  & \(a\) = 5.2946 (1) & \(a\) = 5.2948 (1) & & & & & \\  & \(b\) = 5.3740 (1) & \(b\) = 5.3749 (1) & 1.48/1.49 & 400–500/ & 400–500/ & n/a & n/a \\  & \(c\) = 12.4498 (3) & \(c\) = 12.4488 (3) & & & 400–500/ & 400–500/ & \\  & \(V\) = 354.24 (2) & \(V\) = 354.28 (2) & & & & & \\ \hline \end{tabular}  
* _a_/_b_*100%; \({}^{2}\) slope of (V(T)\({}^{1/3}-V(RT)\)\({}^{1/3})/V(RT)\({}^{1/3}-\) T.  
\end{table} 
Table 4: Results of the in-situ XRD study of the NCNCO00-NCNCO04 samples: unit cell parameters (UCP) and unit cell volume (UCV) (collected at room temperature), temperatures of the phase transition (_T\({}_{pl}\)_), and calculated values of the volumetric thermal expansion coefficient (VTEC).