Abstract Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed that the (C2H5NH3)2MnCl4 crystal undergoes α-β-γ phase transitions at approximately TC2 = 225 K and TC1 = 424 K, remains stable until 470 K, and displays a weight loss of 25.24% at around 579 K due to partial thermal decomposition. Cation dynamics near these temperatures was investigated by MAS 1H NMR and MAS 13C NMR experiments. The small changes in the 1H chemical shift for C2H5 near TC2 are consistent with the transition from the orthorhombic γ-phase to the orthorhombic β-phase. Also, the abrupt changes in NMR signals near TC1 correspond to structural change from the orthorhombic β-phase to the tetragonal α-phase. The 13C spin-lattice relaxation time in the rotating frame (T1ρ) below TC2 is shorter for CH3 than that for CH2, due to the greater mobility at the free end of the alkyl chain. In addition, the temperature-dependent ferroelastic domain structure was studied near the α-β phase transition. There was no noticeable temperature dependence in 1H and 13C T1ρ values at TC1 and TC2, whereas the change in the domain wall was prominent near TC1.

中文翻译：

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钙钛矿 (C2H5NH3)2MnCl4 晶体的 α→β→γ 相变中的热稳定性、阳离子动力学和铁弹性畴壁

摘要 差示扫描量热法 (DSC) 和热重分析 (TGA) 证实 (C2H5NH3)2MnCl4 晶体在大约 TC2 = 225 K 和 TC1 = 424 K 时发生 α-β-γ 相变，在 470 K 之前保持稳定，并显示出由于部分热分解，在 579 K 附近重量损失 25.24%。通过 MAS 1H NMR 和 MAS 13C NMR 实验研究这些温度附近的阳离子动力学。TC2 附近 C2H5 的 1H 化学位移的微小变化与从正交 γ 相到正交 β 相的转变一致。此外，TC1 附近 NMR 信号的突然变化对应于从正交 β 相到四方 α 相的结构变化。TC2以下旋转坐标系中的13C自旋晶格弛豫时间（T1ρ），CH3比CH2短，由于在烷基链的自由端具有更大的流动性。此外，研究了α-β相变附近的温度依赖性铁弹性域结构。TC1 和 TC2 的 1H 和 13C T1ρ 值没有明显的温度依赖性，而畴壁的变化在 TC1 附近很明显。