Abstract: CaCu3Ti4O12 (CCTO) barrier layer ceramic capacitor was prepared by a two-step sintering
process. The CCTO powders were pre-synthesized at 900oC by solid-state reaction and the effects of the
amount of CuO on the formation of the CCTO powders were investigated. The CCTO ceramics were
prepared by the second-step sintering. It was found that the abnormal grain growth and inhomogeneous
microstructure are controlled by the amount of excessive CuO. The optimized CuO content in the
composites is ~14 wt%. The maximum permittivity is 115,000 (1 kHz, 210oC).
Abstract: CaCu3Ti4O12 (CCTO) ceramics were prepared by cold isostatic press (CIP) forming combined
with the conventional sintering method. The effects of calcining temperature on properties of CCTO
ceramics were investigated. The dielectric properties as the function of temperature at typical frequencies
were measured in the temperature range from 243 to 363 K. In addition, the dielectric properties and
complex impedances at room temperature were analyzed in a frequency range from 20 Hz to 106 Hz. The
results showed that CCTO ceramics with dielectric constant higher than 104 were obtained. Compared
with the dry press forming, CCTO ceramics prepared by CIP had more homogeneous grains, less porosity
and better dielectric properties.
Abstract: CaCu3Ti4O12 (CCTO) ceramic thick films have been prepared on Copper substrate, using
ceramic powders by an aerosol deposition method (ADM). The ceramic powders are prepared by
traditional solid state reaction processing at 1100 oC for 5 h. X-ray diffraction and scanning electron
microscopy are used to investigate the microstructure and the phase composition of the deposited films.
The results indicate that thick films are pure CCTO phase and homogenous. The dielectric impedance
spectra indicate that the dielectric constant of CCTO thick film can reach 3×103.
Abstract: CaCu3(Ti1-xZrx)O12 ceramics (x = 0.02, 0.04, 0.06, 0.08) were prepared by the conventional
solid-state reaction method. Phase compositions, microstructure and dielectric properties were examined
by XRD, SEM and impedance spectroscopy, respectively. The experimental results indicated that there is
no obvious effect on microstructure characteristic by substituting Zr4+ for Ti4+. It was found that the
values of the dielectric constant for all of the samples dropped into the order of 102, which is significantly
lower than the order of 105 that of normally reported in the literature. It was suggested that the presence of
impurity phases played an important role for the degeneracy of dielectric properties.
Abstract: Ba5(Nb1-xVx)4O15 (0≤x≤0.1) ceramics doped with H3BO3 were prepared by solid-state reaction.
The effects of H3BO3 additives on the sinterability and microwave dielectric properties of the ceramics
were investigated. The formation of a single phase was identified with the X-ray powder diffraction
patterns of Ba5(Nb1-xVx)4O15 ceramics in the composition x from 0 to 0.025. Minor phases including
Ba3(VO4)2 were formed as the secondary phase for the compositions with x>0.025. The dielectric
constants (εr) of the ceramics increased firstly from 38.7 to 39.69 with x increasing from 0 to 0.01, and,
then decreased to 36.91 with x=0.1, meanwhile, the unloaded quality factor and temperature coefficient
of resonance frequency (τf) decreased as the x value increased from 0 to 0.1. Microwave dielectric
properties, εr=36.91, Q×f =16,167GHz and τf =35ppm/°C, were obtained for Ba5(Nb0.9V0.1)4O15 ceramics
with 1wt% H3BO3 sintered at 900°C for 2h.
Abstract: In this study, it would be interesting to investigate ceramic material based on
Sr0.4Ba0.6Nb2O6 composition, V2O5 was used to substitute Nb2O5 to form the compositions of
Sr0.4Ba0.6Nb2-xVxO6, where 0 ≤ x ≤ 0.3. The prepared Sr0.4Ba0.6Nb2-xVxO6 ceramics were sintered
from 1060oC to 1300oC, and the needed sintering temperatures were dependent on V2O5 content. The
SEM micrographs showed that even 1220oC was used as the sintering temperature of Sr0.4Ba0.6Nb2O6
ceramics, the pores were still observed. The crystal intensities of some (h,k,l) planes, for example
(3,2,0) and (5,5,0) planes, apparently increased with the increase of V2O5 content and slightly
decreased with the increase of sintering temperatures. The temperature-dependent dielectric
characteristics were measured from 25oC to 300oC at 1MHz as a function of sintering temperatures
and V2O5 content. The studied results would show that the sintering temperatures and V2O5 content
also had large influence on the maximum dielectric constants (revealed at Curie temperatures) and the
temperature-dielectric curves of Sr0.4Ba0.6Nb2-xVxO6 ceramics.
Abstract: With citric acid as chelating agent, ethylene alcohol as etherification agent and water as
solvent, NaNbO3 nanopowder was synthesized by citrate sol-gel method. The effects of amount of CA
and EG, pH value on the stability of the precursor sol were investigated. The evolution of NaNbO3 crystal
phase was also investigated by XRD and TG-DTA. The results showed that a homogeneous precursor sol
was formed at in the case of n(CA) : n(metal ion)=3:1, n(CA) : n(EG)=1: 2 and 1:3 and pH=7.5. Sintering
process largely influences the morphology of the prepared products. Grain-like nanoparticles could be
obtained with a rapid temperature rising rate, while nanorods were obtained with a slow rate. The forming
mechanism of different morphologies of the prepared nanoparticles was also discussed.
Abstract: Ca(Al1/2Nb1/2)O3 (CAN) and Ca(Fe1/2Nb1/2)O3 (CFN) were prepared by solid reaction route.
With the sintering temperature increased, the Q×f value of CAN changes from 7 200 to 17 500 GHz due to
the changing of the ordering degree, whereas, the dielectric constant and Q×f value of CFN decrease
remarkably without structural changing. The reason of this phenomenon is that the difference in size of
two B-site ions in CAN is larger than that in CFN. As a result, the ordering degree of CAN is more
sensitive to the conditions of sample preparation, compared with CFN.
Abstract: (1–x)CaTiO3–xNdAlO3 (CTNA) microwave dielectric ceramics have a high Q value and a low
temperature coefficient of resonant frequency ( τf ). CTNA ceramic powder was synthesized using a
polymeric precursor derived from a mixed-metal ethylenediaminetetraacetic acid (EDTA) / ethylene
glycol solution. The precursors and derived oxide powders were characterized by thermogravimetric
analysis and X-ray diffraction. When x = 0.3, CTNA was synthesized at 900°C for 3 h in air. Compared
with that prepared by the solid-state reaction method in literatures, the CTNA ( x = 0.3 ) ceramics with
better microwave properties could be obtained at lower calcination and sintering temperatures by EDTA
Abstract: The variations of dc conductivities (σ) of the Sr2-xLixFeMnO6 double perovskite system over a
range of temperatures (100 ~ 300 K) and for several concentrations (0≤ x ≤ 0.4) of incorporated Li+ ions
are well described by the equation σ = (B/T) exp(−Ea/kT) and show a decrease with decreasing
temperature for a given doping. At a given temperature, σ tends to decrease with increasing x. The derived
activation energy shows a gradual increase with x with a range of values that are lower than what is
usually reported. The measured ac impedance is used to extract the relaxation frequencies as a function of
composition and temperature.