Vibrational properties of CaO(CaMnO₃)_m (m = 1, 2, 3, and ∞) thermoelectric (TE) oxides for high-temperature energy conversion applications are studied both experimentally and computationally. Density functional theory (DFT) calculations reveal strong scattering events involving dispersive acoustic phonons and non-dispersive optical modes in the frequency range of 3–5 THz. We demonstrate that the low frequency parts of the phonon spectra are strongly dominated by Ca-sublattice oscillations for all compounds of the CaO(CaMnO₃)_m (m = 1,2,3, ∞) series, which predicts enhanced phonon scattering upon Ca-sublattice site substitution defects. Accordingly, laser flash analysis (LFA) indicates considerable decrease of thermal conductivity (κ) due to La- substitution for Ca, whereas Nb- substitution for Mn-sites does not affect κ noticeably. It is found that thermal conductivity of CaO(CaMnO₃)_m compounds is governed by phonon scattering on CaO/CaMnO₃ boundaries for m = 1, 2, and 3 and by Umklapp processes for m = ∞. Thermal transport in this system is strongly dominated by acoustic phonon modes possessing much larger Grüneisen parameters (γ) compared to optical ones.

通过实验和计算研究了用于高温能量转换应用的CaO（CaMnO ₃）_m（m = 1、2、3和∞）热电（TE）氧化物的振动特性。密度泛函理论（DFT）计算揭示了在3–5 THz频率范围内涉及色散声子和非色散光学模式的强散射事件。我们证明，对于CaO（CaMnO ₃）_m的所有化合物，声子谱的低频部分主要由Ca亚晶格振荡决定（m = 1,2,3，∞）级数，它预测在Ca-亚晶格位点置换缺陷后声子散射会增强。因此，激光闪光分析（LFA）表明，由于La取代Ca，导致热导率（κ）大大降低，而Mn部位的Nb取代则对κ没有明显影响。已经发现，对于m = 1、2和3 ，CaO（CaMnO ₃）_m化合物的导热系数受CaO / CaMnO ₃边界上的声子散射影响，对于m =∞则受Umklapp过程控制。该系统中的热传输主要由声子声子模式主导，声子声子模式与光学参数相比具有更大的Grüneisen参数（γ）。