The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y_2/3Cu₃Ti₄O₁₂ Ceramics

Abstract

The effects of La concentration on the electrical conductivity and electric modulus of Y2/3−xLaxCu3Ti4O12 ceramics (0.00 ≦ x ≦ 0.20) were investigated in detail. Proper amount of La substitution in Y2/3−xLaxCu3Ti4O12 ceramics made the dielectric loss decreased. When x = 0.10, Y2/3−0.10La0.10Cu3Ti4O12 ceramics exhibited the highest grain‐boundary resistance (0.893 MΩ) and the lowest dielectric loss (about 0.025 at 1 kHz), meanwhile the samples exhibited a relatively high dielectric constant above 6000 over a wide frequency range from 40 Hz to 1 MHz. The decreased dielectric loss was attributed to the enhanced grain‐boundary resistance. With the increase in La concentration, the dielectric relaxation behaviors correlated with the grain‐boundary effects were significantly enhanced. By La doping, the activation energies for the conduction in grain boundaries were slightly depressed, and the activation energies for the relaxation process in grain boundaries were slightly changed. Based on the activation values, it can be concluded that the doubly ionized oxygen vacancies VO∙∙ had substantial contribution to the conduction and relaxation behaviors in grain boundaries.

Low dielectric loss, dielectric response, and conduction behavior in Na-doped Y2/3Cu3Ti4O12 ceramics

“…The lattice distortion resulted from the substitution ions with larger radius may improve the formation of Cu-rich and Ti-poor grain-boundary layer, which can enhance the resistance of the grain boundaries. [12][13][14][15][16][17][18] Na ions have a much larger radius (0.102 nm) than that of Y ions (0.090 nm). Therefore, it is expected that the introduction of the Na ions to the Y sites in YCTO ceramics would tune the resistances of grain boundary and grain as well as realize the decrease of the dielectric loss.…”

Effects of Cu stoichiometry on the microstructure, electrical conduction, and dielectric responses of Y2/3Cu3Ti4O12

“…It can also be seen in Fig. 7 that by increasing x, the low-temperature dielectric loss humps (corresponding to Step 1) are intensified, which may be linked with the increased grain boundary resistance [20]. Therefore, it can be concluded that the low-temperature dielectric relaxation (Step 1) is attributed to the grain boundary effect.…”

“…For CCTO ceramics, the insulating grain boundary and semiconducting grain have been determined to be Cu-rich and Cu-deficient phase, respectively [9][10][11][12][13][14]. It is known that the lattice distortion derived from the substitution ions with larger radius may improve the formation of Cu-rich grain-boundary layer which could enhance the resistance of the grain boundaries [8,[15][16][17][18][19][20][21]. Since the existence of Cu-rich phase plays an important role in the formation of insulating grain boundary, it is wondered whether the resistance of grain boundary could be modified by changing Cu stoichiometry in YCTO ceramics.…”

Effects of Y doping ions on microstructure, dielectric response, and electrical properties of Ca1−3x/2Y x Cu3Ti4O12 ceramics

“…Furthermore, Ln 3? -doped ACu 3 Ti 4 O 12 ceramics have also been reported [21,23,29,32]. It was found that these Ln 3?…”

“…Unfortunately, the loss tangent (tand) values of CaCu 3 Ti 4 O 12 and related ceramic oxides are still higher than the standard value for capacitor applications, making them unsuitable for capacitor applications [1,5,6,8,10,13,23,28,29]. Investigation to reduce tand value is an important and urgent issue that should be intensively performed [8,10,14,21,[29][30][31]. To overcome this problem, the dielectric properties of CaCu 3 Ti 4 O 12 ceramics substituted by Ln 3? ions have been widely investigated, where Ln 3?…”