Microstructure and colossal permittivity of CaTiO₃ ceramics covered with nano-sized CuO and TiO₂ by the hydrothermal method

Abstract

In this work, the CaTiO3-based powders covered with nano-sized CuO and TiO2 particles were obtained by the hydrothermal method (CuO/CaTiO3 (molar ratio) =0.2, and TiO2/CaTiO3 (molar ratio) =0, 0.05, 0.10,...

Giant dielectric response and grain heterogeneity of Y2/3Cu3Ti4O12–TiO2 composite ceramics fabricated by hydrothermal process

“…The specific impedance fit data for the different samples are shown in Table S2. Earlier studies have verified that the intra‐grain domain boundary or subgrain boundary barrier can form the nano‐barrier layer capacitive structure (NBLC), which can be observed by the fitted RC element in the high‐frequency region 23,25 . It can still be seen from Figure 4 that obvious subgrain boundaries in the YCTO−TiO 2 ceramics, which may be the main driving factor for the electrical heterostructure of the grains, and the corresponding response areas are shown in Figure 5E.…”

“…This process co‐occurred during the in situ solid‐state reaction and ceramic sintering due to the lower activation energy required and the high activity of nano‐TiO 2 , resulting in a difference in the TiO 6 octahedron and unit cell size, consistent with the above analysis. Furthermore, according to our previous studies, 23 the $${\rm{Ti}}_{{\rm{Cu}}}^{ \bullet \bullet }$$ donor defect can also appear in the YCTO‐TiO 2 ceramics, drastically increasing the weakly trapped electrons. The YCTO crystal and these defects are shown in Figure 3.…”

“…Earlier studies have verified that the intra-grain domain boundary or subgrain boundary barrier can form the nano-barrier layer capacitive structure (NBLC), which can be observed by the fitted RC element in the high-frequency region. 23,25 It can still be seen from Figure 4 that obvious subgrain boundaries in the YCTO−TiO 2 ceramics, which may be the main driving factor for the electrical heterostructure of the grains, and the corresponding response areas are shown in Figure 5E. Electron conduction at subgrain boundaries is a thermally activated process, and this interface is beneficial for the improvement of dielectric properties.…”

“…[20][21][22] Moreover, the nanoscale barrier layer capacitance structure formed by special interfacial barriers in the CCTO composite ceramic grains substantially improves dielectric properties while maintaining relatively low dielectric loss. [23][24][25][26] However, it is still unclear whether there are similar structures in other ACTO system ceramics and whether it motivates the heterogeneity of YCTO grains. In addition, excess TiO 2 can promote the electron hopping between Cu + /Cu 2+ and Ti 3+ /Ti 4+ ions in CCTO to enhance the grain semiconducting properties, ultimately leading to an increase in dielectric constant (see Table S1 for details).…”

“…Recent studies have shown that grain heterogeneity is more pronounced in pure‐phase YCTO ceramic than in CCTO and has not been effectively elucidated 20–22 . Moreover, the nanoscale barrier layer capacitance structure formed by special interfacial barriers in the CCTO composite ceramic grains substantially improves dielectric properties while maintaining relatively low dielectric loss 23–26 . However, it is still unclear whether there are similar structures in other ACTO system ceramics and whether it motivates the heterogeneity of YCTO grains.…”