Page 329 - Read Online

Fujii et al. Microstructures 2023;3:2023045 https://dx.doi.org/10.20517/microstructures.2023.43 Page 5 of 14

Figure 2. P-E loops measured at room temperature for (A) undoped BaTiO ceramics with a grain size of 1.2 µm and 76 µm, (B)
3
-9
-9
-2
-2
undoped BaTiO ceramics sintered at 10 atm pO and 10 atm pO , (C) formulated BaTiO ceramics sintered 10 atm pO and 10
2
3
3
2
2
atm pO , and (D) model MLCCs with various grain sizes. The ac frequency was 10 Hz.
2

Figure 3. Temperature and the ac field dependence of the dielectric constant of a BaTiO ceramics with a grain size of 1.2 mm. The ac
3
field frequency was 100 Hz. The peaks in the permittivity correspond to the phase transition in BaTiO ; on increasing temperature, the
3
material transforms from a rhombohedral ferroelectric to an orthorhombic ferroelectric to a tetragonal ferroelectric to a paraelectric
cubic structure.
nonlinearity is observed in the rhombohedral, orthorhombic, and tetragonal ferroelectric phases of BaTiO .
3
Although not shown here, the domain wall motion contributions to the small signal properties are gradually
lost as the temperature approaches 0 K .
[29]

The magnitude of the temperature dependence of the extrinsic contributions to the properties is a function
of the grain size of the ceramics, as can be seen in comparing the data in Figures 3-5 (Figure 3 uses the same
data as Figure 5, and Figure 5 has more data). Figure 4 shows selected data for the dielectric nonlinearity for
a large-grained (76 mm average grain size) BaTiO ceramics. One consequence of the increased domain wall
3
mobility in large-grained materials is that the electric fields at which the materials transition from Rayleigh-