Qin Jincheng, Liu Zhifu, Ma Mingsheng, Liu Feng, Qi Ze-Ming, Li Yongxiang
CAS Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China.
Center of Materials Science and Optoelectronics Engineering, The University of Chinese Academy of Sciences, Beijing 100049, China.
ACS Appl Mater Interfaces. 2021 Apr 21;13(15):17817-17826. doi: 10.1021/acsami.1c01909. Epub 2021 Apr 9.
Structure and dielectric properties of gillespite-type ceramics ACuSiO (A = Ca, Sr, Ba) were investigated by crystal structure refinement, far-infrared reflectivity spectroscopy, and microwave dielectric measurements. A series of (CaSr)CuSiO (0 < < 1) ceramics with relative permittivities of 5.70-5.82, × values of 20391-48794 GHz (@ ∼ 13.5 GHz), and τ of -46.3 to -38.9 ppm/°C were synthesized. By Ca substitution for Sr at the A-site, the rigid double-layered copper silicate framework remains stable, resulting in the nearly unchanged relative permittivity, while the [(Ca,Sr)O] dodecahedron undergoes shrinkage and distortion, which is correlated to the changes in the × and τ values. The normalized bond valence sums indicate that almost all ions are rattling, weakening the bond strengths and enlarging the molecular dielectric polarizability. The fitting of far-infrared reflectivity spectra reveals that the local structure changes suppress the intermediate and low-frequency vibrational modes significantly and improves the contribution from electronic polarization to permittivity. Symmetry breaking of the [(Ca,Sr)O] dodecahedron conforms to the elevated restoring forces acting on the ions and improves the τ value. The large span in × value may have intricate correlations to local structure changes and defects. Machine learning methods were introduced to explore the decisive structural factors for the × value. A × value prediction model correlated with the A-O2 bond length and the variance of A-O bond lengths was established. The × values of isostructural (BaSr)CuSiO ceramics were predicted and verified by experiments.
通过晶体结构精修、远红外反射光谱和微波介电测量，研究了硅铜钡石型陶瓷ACuSiO（A = Ca、Sr、Ba）的结构和介电性能。合成了一系列相对介电常数为5.70 - 5.82、×值为20391 - 48794 GHz（@ ∼ 13.5 GHz）且τ为 - 46.3至 - 38.9 ppm/°C的（CaSr）CuSiO（0 < < 1）陶瓷。通过在A位用Ca取代Sr，刚性双层硅酸铜骨架保持稳定，导致相对介电常数几乎不变，而[(Ca,Sr)O]十二面体发生收缩和畸变，这与×值和τ值的变化相关。归一化键价和表明几乎所有离子都在晃动，削弱了键强并增大了分子介电极化率。远红外反射光谱的拟合表明，局部结构变化显著抑制了中频和低频振动模式，并提高了电子极化对介电常数的贡献。[(Ca,Sr)O]十二面体的对称性破缺符合作用于离子的增强恢复力，并提高了τ值。×值的大跨度可能与局部结构变化和缺陷有复杂的相关性。引入机器学习方法来探索×值的决定性结构因素。建立了与A - O2键长和A - O键长方差相关的×值预测模型。通过实验预测并验证了同结构（BaSr）CuSiO陶瓷的×值。
