Abstract: Hexagonal MgAl2O4 spinel fibers were synthesized at 1500oC for 6h in nitrogen atmosphere.
The structure and morphology of the fibers were investigated using X-ray diffraction (XRD) and scanning
electron microscopy (SEM). The fibers grew via vapor- liquid- solid mechanism. The twin mechanism
was suggested to play a key role in the formation process of the hexagonal fibers.
Abstract: Dielectric constant and dielectric dissipation of MgAl2O4 transparent nano-ceramics were
measured at different frequencies. The results indicated that the transparent nano-ceramic has a very low
dielectric constant and low dielectric dissipation in frequency range of 1K~9MHz, but the dissipation of is
independent of frequency. The dielectric constant of the transparent nano-ceramic does not vary signifycantly
Abstract: To determine the optimal doping concentration, a series of Mn:MgAl2O4 were successfully
prepared through vacuum-sintering with the highest doping concentration up to 35%. Samples with a low
doping concentration exhibit a light green color. When the doping concentration increases, its color
becomes deeper and deeper and when the doping concentration reaches 14%, their colors become brown
and deeper brown when their concentrations further increase. The crystal phases of the samples were
manifested by XRD measurements and their photoluminescence properties were studied. Combined with
phase analysis, optimal doping concentration of transparent ceramics has been determined. In addition,
the mechanism for fluorescence of Mn:MgAl2O4 transparent ceramics has also been discussed.
Abstract: 5.0at% and 10.0at% Mn-doped MgAl2O4 transparent ceramics have been prepared through
vacuum sintering (1750°C /2h) and subsequent hot isostatic pressing (HIP) (1650°C /2h). The effect of
microstructure on the light transmittance of the sintered MgAl2O4 is discussed. Results showed that the
grains became dense and grain boundary became clear and most of pores inside and between grains were
removed, so the transmittance of two samples increased. The optical transmittance of the 5.0at%
specimens was increased by one times in the visible light wavelength region. HIP treatment has a great
effect on improving the transparency of samples with low doping concentrations.
Abstract: Yttrium aluminum garnet (YAG) nanopowders were synthesized by n-amyl co-precipitation
method. Transparent YAG ceramics were achieved by sintering the green body at 1800°C and then
1600°C for ten hours with TEOS as sintering additive. The transmittance of the sample was 75% at visible
wavelength of 800nm.
Abstract: Pure-phase 2at% Nd:YAG powder was synthesized by alcohol-water co-precipitation method.
2at% Nd:YAG ceramics were sintered at 1780 °C for 10 h under vacuum using the powder. Sintering
ability of the powder was studied by comparing the results of alcohol-water solvent with those of distilled
water solvent. The effects of different volume ratios of alcohol to water (R) on transparent ceramics have
been also studied. Transparent ceramics having a transmittance of 40% in the visible wavelength have
been sintered without sintering additive using the powder (R=0.8), which is much better than ceramics
(16%) prepared using the powder derived from distilled water solvent under the same sintering
conditions. In addition, the different R does not have much influence on the transmittance of ceramics in
the present work. Compared with the results of distilled water solvent, the powders, using alcohol-water
mixtures with different R as solvent, are more beneficial to the sintering of high transparent ceramics.
Abstract: In this paper, pure phase Nd-doped YAG powders were prepared by co-precipitation method
with different amount of MgO (0~ 0.6 wt %) as additive. Transparent Nd:YAG ceramics were fabricated
by vacuum sintering at 1750°C for 10 hours using the powders. Microstructure of the surfaces of
thermally etched Nd:YAG ceramics was observed by SEM. Transmittance of the transparent Nd:YAG
ceramics was measured over the wavelength region from 600nm to1200nm. The results showed that
MgO as sintering aid can restrain abnormal grain growth and reduce pores in grains and at the same time,
optical transmittance of the ceramics was increased. The optimal weight percentage of MgO added can be
determined as 0.3wt % for the fabrication of transparent Nd:YAG ceramics.
Abstract: By means of co-precipitation, pure YAG phase was synthesized from the reaction of aluminum
yttrium and cerium nitrates with ammonia as precipitator. In order to obtain the special coating oxide
precursor, the metal ions solution and ammonia were respectively added with fixed ratio by two
peristaltic pumps to maintain an expired pH value and reaction rate. The as-received precursor was
annealed at 700°C and 900°C respectively. The structure, phase evolution and morphology of the
as-prepared YAG nanopowders were tested by XRD, BET and SEM. At lower temperature (900°C),
coating oxide precursor was directly transformed to nanopowders of pure YAG phase. The high salt
solution concentration was critical for the control of chemical homogeneity within the precursors. The
YAG nanopowders were less-aggregated and better-dispersed. The luminescent properties were
examined and discussed.
Abstract: Nd:Gd2O3-HfO2 powder has been prepared with a co-precipitation method. The size of
Nd:Gd2O3-HfO2 powder is near 50nm. Transparent Nd:Gd2O3-HfO2 ceramics were successfully fabricated
by sintering the powder compact at 1800°C under H2 atmosphere. The synthesis process and optical
properties were investigated in detail. By measuring the optical properties of transparent Nd:Gd2O3-HfO2
ceramics, we found that the absorption bond of Nd ions near 808nm is enlarged, and the FWHM of the
emission bond near 1060nm is near 25nm. It was believed that Nd:Gd2O3-HfO2 transparent ceramic is
potential laser material for the usage in solid-state heat-capacity laser(SSHCL) application.
Abstract: Single-phase aluminum oxynitride powders were obtained by varying the holding temperature
(T) and the weight percentage of α-Al2O3 in Al2O3 (X) with nano-sized Al2O3 and AlN powders as raw
materials. Influences of T and X on the phase composition of obtained powders were studied. The results
showed that the content of aluminum oxynitride increased with increasing T or X. When X was 50% and
T was 1750°C, obtained powders had better properties than those of others.