Effects of CuO Doping on the Microstructural and Dielectric Properties of Ba_0.6Sr_0.4TiO₃ Ceramics

Abstract

This study investigates the effect of CuO on the sintering behavior, dielectric properties, and microstructures of Ba0.6Sr0.4TiO3 (BST) ceramics. The ceramics were sintered in air at temperatures ranging from 1000° to 1230°C. It is found that a small amount of added CuO (0.6 mol%) can significantly increase the density and improve the dielectric properties of BST ceramics. Doped BST ceramics can be sintered to a density >95% of the theoretical density at 1150°C. scanning electron microscopic observations show that the BST grain sizes increase with increasing amounts of CuO. No secondary phases in the BST ceramics are observed using X‐ray diffraction pattern for CuO additions up to 0.9 mol%. However, compositional analysis using transmission electron microscopy‐EDX for the BST ceramics with 0.9 mol% CuO sintered at 1150°C showed that a small level of secondary phase formation is present. On the other hand, large dislocations are observed for BST with 0.6 mol% CuO addition as a result of lattice distortion, which creates the vacancy condensation because of the atomic mismatch in the solid solutions. Optimal CuO doping concentrations can reduce the loss tangents of BST that can also ensure a high dielectric constant. When the doping concentration of CuO is 0.6 mol% and the ceramic is sintered at 1150°C, the BST ceramic has the following properties at 1 MHz: dielectric constant=4094, tan δ=0.55%.

Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O3 lead-free ceramics

“…Moreover, the average grain sizes increase from about 2.8 to 11.0 lm with the increase of sintering temperature from 1200°C to 1475°C. The increase of grain sizes should be attributed to the part occupation of Li + for the lattice of ABO 3 perovskite structure, which generates proper oxygen vacancies in BCTZL ceramics, and these defects can accelerate the mass transport process, further promoting the grain growth [23]. On the other hand, the ceramics can be well sintered at a relatively low temperature range (1350-1450°C) by doping with Li + (vs BCTZ, 1540°C [12]).…”

Dielectric behavior of perovskite glass ceramics

“…The value of e r increases with increasing amount of CuO up to 0.6 mol% but it decreases at 0.9 mol% due to formation of secondary phase. The Curie temperature for Cu-doped BST is 5.0°C, which is lower than that of undoped sample (T c = 7.1°C) [151].…”

Electrical and magnetic properties of low-temperature sintered xBa0.6Sr0.4TiO3+(1−x)Ni0.2Cu0.2Zn0.62O(Fe2O3)0.98 composite ceramics

“…For all samples, r values increase with increasing sintering temperature and then decrease slightly after reaching their respective maximum values. The each peak position shifts to a higher temperature with an increase of BST content x, due to a higher sintering temperature of BST (1350 • C) [24]. The relative densities of all specimens are above 95% when the sintering temperature is higher than 925 • C, indicating that the BST + NiCuZn ferrite composite ceramics can be sintered within a large temperature range (925-1050 • C).…”

“…This may be explained by the fact that some of Ni 2+ (coordination number N = 6, ionic radius r = 0.69 Å) or Cu 2+ (N = 6, 0.73 Å) ions [23] enter the Ti 4+ (N = 6, 0.605 Å) site of perovskite BST, resulting in an increase of unit cell volume with a shift of diffraction peaks toward lower angles. However, the solubility limit of active Cu 2+ ion in BST is only 0.6 mol%, which leads to the unobvious change for the most strong diffraction peak (2 2 0) of BST when the BST content is more than 10 wt.% [24]. In addition, the most intense diffraction peak (3 1 1) of the ferrite shifts toward higher angles for the composite ceramics.…”

“…This is partly due to a decrease of dielectric loss of BST in a case that some of Ni 2+ or Cu 2+ ions substitute for Ti 4+ in BST (Fig. 1) [24]. which gives the behavior of materials when excited by an external magnetic field.…”