## 2 Experimental Part
The  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**T, K**} & \multicolumn{2}{c}{**C\({}^{0}_{\text{p}}\)(T), J/(mol\(\cdot\)K)**} \\ \cline{2-3}  & **Our Data** & **Data in [26]** \\ \hline
180 & 44.50 & 43.83 \\
230 & 64.86 & 61.18 \\
250 & 70.37 & 67.08 \\
280 & 77.07 & 74.82 \\
300  
results of the heat capacity study of BaTiO\({}_{3}\), presented in Table 4 and Figure 7, cover the temperature range of 298.15-673 K. These data allow the comparison of phase transitions in BaTiO\({}_{3}\) with similar processes in neodymium manganites, evaluating the similarities and differences in heat capacity behavior and structural transitions between these materials. It should be noted that the experimentally obtained standard heat capacity value for BaTiO\({}_{3}\), equal to 101 \(\pm\) 7 J/(mol\(\cdot\)K), aligns well with the reference value of 102.45 J/(mol\(\cdot\)K), calculated based on the temperature dependence equation for heat capacity [J/(mol\(\cdot\)K)] [28]:  
\[\mathrm{C^{0}_{p}=121.46+8.535\times 10^{-3}\;T-19.163\times 10^{5}\;T^{-2}\;(298.1 5-1800\;K).} \tag{4}\]  
The experimental value of \(\mathrm{C^{0}_{p}(298.15)}\) for BaTiO\({}_{3}\) aligns well with its calculated value of 100.3 J/(mol\(\cdot\)K), determined using the method of ionic entropy increments [29] according to the scheme:  
\[\mathrm{S^{0}(298.15)\;BaTiO_{3}=S^{i}Ba^{2+}+S^{i}TiO_{3}{}^{2-},} \tag{5}\]  
where \(S^{i}Ba^{2+}\) and \(S^{i}TiO_{3}{}^{2-}\) are the ionic entropy increments, equal to 28.4 and 71.9 J/(mol\(\cdot\)K), respectively [29]. \begin{table}
\begin{tabular}{c c c c c c} \hline
**T, K** & \(\mathbf{C_{p}\pm\overline{\delta}}\) & \(\mathbf{C^{0}_{p}\pm\frac{\circ}{\Delta}}\) & **T, K** & \(\mathbf{C_{p}\pm\overline{\delta}}\) & \(\mathbf{C^{0}_{p}\pm\frac{\circ}{\Delta}}\) \\ \hline
298 & 0.4319 \(\pm\) 0.0114 & 101 \(\pm\) 7 & 498 & 0.4331 \(\pm\) 0.0036 & 101 \(\pm\) 3 \\
323 & 0.4583 \(\pm\) 0.0120 & 107 \(\pm\) 8 & 523 & 0.4669 \(\pm\) 0.1229 & 109 \(\pm\) 4 \\
348 & 0.47083 \(\pm\) 0.0105 & 110 \(\pm\) 7 & 548 & 0.5041 \(\pm\) 0.0087 & 118 \(\pm\) 8 \\
373 & 0.49223 \(\pm\) 0.0102 & 115 \(\pm\) 7 & 573 & 0.5110 \(\pm\) 0.0069 & 119 \(\pm\) 9 \\
398 & 0.5330 \(\pm\) 0.0049 & 124 \(\pm\) 3 & 598 & 0.5382 \(\pm\) 0.0107 & 126 \(\pm\) 7 \\
423 & 0.3279 \(\pm\) 0.0083 & 76 \(\pm\) 5 & 623 & 0.5801 \(\pm\) 0.0112 & 135 \(\pm\) 8 \\
448 & 0.3563 \(\pm\) 0.0084 & 83 \(\pm\) 5 & 648 & 0.6000 \(\pm\) 0.0134 & 140 \(\pm\) 7 \\
473 & 0.3992 \(\pm\) 0.0084 & 93 \(\pm\) 4 & 673 & 0.6210 \(\pm\) 0.0095 & 145 \(\pm\) 6 \\ \hline \end{tabular}
\end{table} 
Table 4: The experimental values of BaTiO\({}_{3}\) heat capacity [\(\mathrm{C_{p}\pm\overline{\delta}}\), J/(g\(\cdot\)K); \(\mathrm{C^{0}_{p}\pm\frac{\circ}{\Delta}}\), J/(mol\(\cdot\)K)]. Figure 7: Temperature dependence of the heat capacity of BaTiO\({}_{3}\). \(\overline{\delta}\)—experimental data, \(\bullet\)—calculated data. As shown in Figure 7 and Table 4, BaTiO\({}_{3}\) exhibits a phase transition at 398 K (125 \({}^{\circ}\)C). According to the literature data [19], this transition occurs at 393 K (120 \({}^{\circ}\)C), where the tetragonal modification of BaTiO\({}_{3}\) transforms into a cubic structure, reaching the Curie point. In [19], the temperature dependence of the specific heat capacity of BaTiO\({}_{3}\) was also studied at heating rates of 1, 3, and 5 K/min, where the phase transition was observed at 395 K, 394.1 K, and 390.9 K, respectively. Given that the \(\Pi\)-C-400 calorimeter measures heat capacity in increments of only 25 K (within the range of 373-398 K), the phase transition temperature of 398 K appears to be accurate. Based on the phase transition temperature (398 K), equations were derived describing the temperature dependence of heat capacity in [J/(mol\(\cdot\)K)].