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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Ceramic Society
Journal Basic Information
Journal DOI :
The Korean Ceramic Society
Editor in Chief :
Volume & Issues
Volume 28, Issue 12 - Dec 1991
Volume 28, Issue 11 - Nov 1991
Volume 28, Issue 10 - Oct 1991
Volume 28, Issue 9 - Sep 1991
Volume 28, Issue 8 - Aug 1991
Volume 28, Issue 7 - Jul 1991
Volume 28, Issue 6 - Jun 1991
Volume 28, Issue 5 - May 1991
Volume 28, Issue 4 - Apr 1991
Volume 28, Issue 3 - Mar 1991
Volume 28, Issue 2 - Feb 1991
Volume 28, Issue 1 - Jan 1991
Selecting the target year
Microstructure and Electrical Properties in
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 347~352
The effects of Ta2O3 doping on the microstructure, electrical properties and thermal expansion in Pb(Zr0.525Ti0.475)O3 ceramics were studied. Density, average grain size, electromechanical coupling factor kp and thermal expansion coefficient of unpoled and poled samples were measured as a function of Ta2O5 content. Average grain size was decreased and density increased above 0.6 mol% Ta2O5 addition. In case of 0.2 mol% addition, density showed minimum according to grain growth. Dielectric constant and electromechanical coupling factor kp were the lowest in 0.2 mol% addition increased with Ta2O5 addition.
Direct Preparation of fine Powders of Bi-Pb-Sr-Ca-Cu-O by Ultrasonic Spray Pyrolysis
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 353~358
Fine powders of the 2212 superconducting phase of bismuth system have been prepared directly from solution using ultrasonic spray pyrolysis. The fine superconducting powders produced by pyrolysis were characterized for the size, shape, and crystalline phase by SEM and XRD. The pyrolysis temperature, flow rate of the carrier gas, residence time of the droplets greatly influenced the size, shape, and crystalline phase. The optimum temperature and flow rate of the carrier gas for the preparation of fine powders of the 2212 superconduting phase were found to be 830
and 3ι/min, respectively.
Low-Temperature Sinterbility of Semiconducting
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 359~364
The effects of Pb5Ge3O11 on the sinterbility and lattice variation of the semiconducting 0.15 mol% Y2O3 doped BaTiO3 have been investigated as functions of additive contents (from 0.25 mol% to 2.5 mol%) and sintering temperatures (from 110
). As the amount of Pb5Ge3O11 increases, the sinterbility of BaTiO3 increases abruptly at around 115
. During the sintering, the most of Pb+2 ions in additives penetrate into BaTiO3 lattices and Ge+4 ions present at grain boundaries. Therefore the c lattice of the BaTiO3 increases largely and then the tetragonality increases due to the diffusion of the Pb+2 ions.
Phase Formation and Rheological Characteristics of LAS Derived from the Monophasic Sol-Gel Route
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 365~372
LAS (lithium aluminosilicate) sol was synthesized using the hydrolysis-condensation reaction of TEOS, chelated Al(OBus)3 and Li-salt with H2O in alcohol (EtOH+2-Propanol) medium. Effects of important reaction parameters on the properties of sol and gel-derived LAS were examined. The crystallization of the sol-gel derived LAS with
-spodumene composition began at ∼600
, and a series of polymorphic transformations occurred as temperature was increased to 1100
: amorphous LAS\longrightarrowhexagonal LiAl(SiO3)2\longrightarrow
-spodumene. Lowering Li content in the gel enhanced densification and retarded the crystallization significantly. Optimum reaction conditions of LAS sol formation for thin coating applications were derived from rheological measurements, and these can be summarized as: H2O/total alkoxides molar ratio=4, pH=∼2.5, and aging time of ∼250h.
Effect of Ca/P Mole Ration on Mechanical Properties of Alumina added Hydroxyapatite
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 373~382
The effect of Ca/P mole ratio (Ca/P=1.60, 1.67, 1.75) in the initial solution on the mechanical properties of alumina added hydroxyapatite was investigated. Hydroxyapatite was synthesized by precipitation method using Ca(NO3)2
4H2O and (NH4)2HPO4 as starting materials and 5 wt% of
-Al2O3 was added to precipitation solution. The powder was calcined at 800
and sintered at 1,150∼1,400
under water vapor atmosphere. With the increasing of Ca/P mole ration in the initial solution, the amount of tricalcium phosphate formed from the decomposition of hydroxyapatite reduced and the sinterability and mechanical properties were increased. The bending strength and Vickers hardness of the specimen sintered at 1,300
with the Ca/P mole ratio of 1.75 in the initial solution were 230 MPa and 650 kg/
, respectively. The improvement of mechanical properties was attributed to not only the effect of Ca/P mole ratio but also the strengthening of sintered body by Al substitution for P ions.
The Analysis of Degradation Phenomena in Piezoelectric Ceramics by Equivalent Circuit Analysis Method
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 383~389
The analysis of degradation phenomena of poled PZT ceramics was investigated relate to piezoelectric equivalent circuit elements. As a result, in the case of impressed mechanical shock on poled specimen of degradation phenomena was explained by domain rearrangement, and in the case of left in air, degradation phenomena was explained by space charge diffusion.
Mechanical Properties of
-Sialon Ceramics Prepared from Wando Pyrophyllite and an Alkoxide
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 390~398
-Sialon powder was prepared from Wando pyrophyllite by the carbothermic reduction and nitridation at 135
for 10 h nitrogen atmosphere. Amorphous silica prepared from Si(OC2H5)4 was added to Wando pyrophyllite powder in order to control the final Z value. Two different methods were applied for synthesis of
-sialon powders. In Process A, the amorphous silica prepared from Si(OC2H5)4 was admixed to Wando pyrophyllite powder. Process B was started from the mixture of Wando Y2O3 was added to the synthesized
-Sialon powders as a sintering aid, and the mixed powders were hot pressed at 175
for 120 min in nitrogen atmosphere under 30 MPa. Their mechanical properties were compared. The maximum values of M.O.R., hardness and KIC were 667 MPa, 16 GPa and 6.3 MN/m3/2, respectively, and they are the values obtained form
-Sialon ceramics prepared by process A of Z=0.5.
Synthesis and Mechanical Properties of Mullite-PSZ Composites by Sol-Gel Process
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 399~405
Mullite-PSZ powders were synthesized by the sol-gel process using Al(sec-OC4H9)3, Si(OC2H5)4, ZrOCl2
8H2O and YCl3 solution and the characteristics of synthesized powders were studied. The sinterability and mechanical properties of powder compacts sintered at 1670
for 4hr were also studied for various PSZ contents.
-Al2O3(Al-Si spinel) formed at 980
from amorphous dried gel, and mullite as well as ZrO2 formed above 1200
. At the room temperature, ZrO2 was a mixture of tetragonal and monoclinic phases. The specimens were densified to 97∼98% except the specimen containing 25 vol% PSZ which showed the relative density of 94%. The K1c value increased with the PSZ content and showed a maximum value of 4.1 MN/m3/2 at 25 vol% PSZ; this value was about 50% higher than that of the mullite without PSZ. Flexural strength had a maximum value of 280 Mn/㎡ at 20 vol% PSZ. In contrast, at 25 vol%, the flexural strength was even lower than that of the mullite possibly due to higher porosity of 6%.
A Study on the Transparent Glass-Ceramics on the MgO-
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 406~414
The composition of base glass was selected as MgO 8, Al2O3 24, SiO2 68 in weight percent. TiO2 and ZrO2 were added to the base glass to investigate their effects as nucleating agents. In the case of ZrO2 addition, the optimum temperature for nucleation, which was related to the precipitation of tetragonal ZrO2, was 80
. The optimum growth condition for the crystal was 87
for 8 hrs, and the major crystal phases precipitated in the samples were
-quartz ss. and mullite. The light transmissivity turned out to be around 80 per cent. On the other hand, when the TiO2 was added, it was difficult to determine the nucleating temperature, because the samples turned easily into translucency during the heat treatment. Therefore, it was almost impossible to retain transparency in the samples. The light transmissivity was below 30 per cent.
A Study on the Microstructural Control of LAS Ceramics (I):
Frit Addition on the Microstructure and Thermal Expansion of
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 415~421
Influence of Li2O.4B2O3 frit addition on the microstructure and thermal expansion properties of
-eucryptite ceramics was studied. With 1.0~10.0wt% frit addition, sintering temperature range was enlarged and densified body was obtained. Thermal expansion was increased from -6.67
-1 of pure sintered body to 1.03
-1 of 6 wt% added body, but this increasement was accompanied by inhibition of thermal expansion anisotropy, so that improved microcracking property.
Microstructure and Mechanical Properties of
-Nb Composites Prepared by Reaction Sintering
Journal of the Korean Ceramic Society, volume 28, issue 5, 1991, Pages 422~428
The reaction sintering of Al2O3-ZrO2-Nb composite has been investigated using Al2O3, and ZrAl2 powders. Two kinds of specimens, 78.3Al2O3-14.0Nb2O5-7.7ZrAl2 in wt.% (AZN-5) and 72.3Al2O3-13.8Nb2O5-7.5ZrAl2-6.4ZrO2(AZN-10), were prepared. Powder compacts were sintered at various temperatures between 1
for 30 min in Ar. DTA and X-ray analysis have showen that a reaction between Nb2O5 and ZrAl2 started at 149
to form Al2O3, ZrO2, and Nb. The sintered density increased with the sintering temperature. AZN-10 specimen showed higher density than AZN-5 specimen for almost all the experimental conditions. Al2O3-ZrO2-Nb composite hot pressed after reaction sintering showed higher toughness and lower hardness than hot pressed Al2O3-ZrO2. The crack propagated through many metallic Nb particles which showed plastic deformation, and this is the cause of the increase in toughness of Al2O3-ZrO2-Nb composite over Al2O3-ZrO2.