• 한국세라믹학회지
• /
• 제29권10호
• /
• pp.822-826
• /
• 1992

SiO2 doped sapphire single crystals were grown by Verneuil method using feed material which prepared by adding SiO2 in Al2O3. Crystal growing were attempted with varing doping amount of SiO2 from 0.01 to 1.0 wt% and when the doping amount of SiO2 were 0.01~0.04 wt%, single crystals could be attained. Starting materials for feed powder were 99.99% purity alumina and extra pure SiO2 powder. Mixing these two materials by wet milling for 24 hours and drying the mixture and then was calcined at 900~110$0^{\circ}C$ for 2~4 hours. The grown crystals had yellowish color and were somewhat transparent. During growing process the flow range of oxygen was 5~7.5ι/min and of hydrogen was 13~25ι/min, the average growth rate was 7.0~11 mm/hr. The pressure of gases were fixed at 5psi. The color of crystal was appeared and mechanical property of sapphire was developed by doping of SiO2.

• 한국재료학회지
• /
• 제24권1호
• /
• pp.33-36
• /
• 2014

This study was aimed at synthesizing and characterizing cerium-doped titania. Cerium-doped anatase titania powders were prepared by sol-gel process, with ammonium (IV) nitrate and titanium (IV) butoxide as the raw materials. The characteristics of pure $TiO_2$ and cerium-doped $TiO_2$ were investigated by XRD, TG/DTA, FE-SEM, and UV-vis spectroscopy. The results of this study show that anatase type of $TiO_2$ was obtained in as-prepared and calcined $TiO_2$ and Ce-$TiO_2$ powder. A DTA curve was also observed as the crystallization temperature decreased with increasing cerium contents. We found that the crystallite size of the obtained anatase particles decreased from 55 nm to 25 nm and the particle size decreased with increasing cerium contents. Moreover, UV-vis spectra showed that anatase titania powders with various cerium contents effectively extend the light absorption properties to the visible region.

• 한국정보전자통신기술학회논문지
• /
• 제1권2호
• /
• pp.27-32
• /
• 2008

A current research basically diverted towards an increase in the operational output with the minimization of the materials used, which ultimately scaled down the dimensions of ceramic electronic components. In this direction the nano-technology pave the revolutionary changes in particular the electronic industries. The applications of nano-sized particles or nano-sized materials are hence, playing a significant role for various purposes. The PZT(lead, zirconium, titanium) based ceramics which, are reported to be ferroelectric materials have their important applications in the areas of surface acoustic waves (SAW), filters, infrared detectors, actuators, ferroelectric random access memory, speakers, electronic switches etc. Moreover, these PZT materials possess the large electro mechanical coupling factor, large spontaneous polarization, low dielectric loss and low internal stress etc. Hence, keeping in view the unique properties of PZT piezoelectric ceramics we also tried to synthesize indigenously the small sized PZT ceramic powder in the laboratory by using the modified sol-gel approach. In this paper, propyl alcohol based sol-gel method was used for preparation of PZT piezoelectric ceramic. The powder obtained by this sol-gel process was calcined and sintering to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology was determined by high resolution scanning electron microscopy.

• 한국전기전자재료학회논문지
• /
• 제37권6호
• /
• pp.662-667
• /
• 2024

In this study, the electrical properties of a C0G (class 1 ceramic) dielectric composition with internal reducibility, specifically (Ba_0.27CaSr)(Zr_0.95Ti_0.05)O₃, were investigated by fixing Ba at the A site and varying the Ca/Sr molar ratio. The potential application of this composition in high-permittivity C0G MLCCs was examined. The powder was calcined at 1,150℃ for 2 hours, as determined by TG-DTA analysis, and the resulting powder was ground to achieve a particle size (D50) of 0.35 to 0.4 ㎛ and a specific surface area (BET) of 4.5 to 5.0 g/m². With a Ca/Sr molar ratio of 0.3, the composition (Ba_0.27Ca_0.17Sr_0.56) (Zr_0.95Ti_0.05)O₃ exhibited electrical properties with a permittivity of 41.9, a loss of less than 0.008%, and an insulation resistance exceeding 2.2×10¹³ Ω. The feasibility of using this composition for high-capacitance C0G MLCCs was confirmed.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
• /
• pp.245-246
• /
• 2006

A propyl alcohol based sol-gel method was used as to replace the 2-methoxyethanol with 1,1,1 tris (hydroxymethyl) ethane for preparation of pzt piezoelectric ceramic. The powder obtained by this sol-gel process were calcined at $900^{\circ}C$ and followed by the sintering at $1100^{\circ}C$ for ca2 hrs as to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology were determined by high resolution scanning electronmicroscopy. Further, the prepared small sized pzt thin powders are likely to be used m various applications.

• 한국세라믹학회지
• /
• 제47권2호
• /
• pp.177-182
• /
• 2010

To synthesize $Gd_2O_3:Eu^{3+}$ phosphor, gadolinium-europium oxalate precursors were prepared from oxalic acid, NaOH or aqueous ammonia via coprecipitation method. The obtained precursors were heat-treated and then characterized by XRD, SEM and PL. The kinds and amounts of coprecipitant (NaOH or aqueous ammonia) were found to affect the powder morphology and properties of gadolinium-europium oxalate precursors. Two crystalline precursors and one amorphous precursor were synthesized. The nanometer-sized amorphous gadolinium-europium oxalate precursor was first prepared using the oxalate coprecipitation technique. The calcined powders obtained from the amorphous precursor were nearly spherical in shape, and a narrow size distribution was obtained. The NaOH coprecipitant was more effective in the preparation of nanometer-sized spherical powders. A thermal decomposition process was conducted for the three kinds of precursors. The photoluminescence property was also measured as a function of europium content, and concentration quenching occurred for samples with europium concentrations of over 10 mol%.

• 한국세라믹학회지
• /
• 제29권3호
• /
• pp.211-215
• /
• 1992

Crack free PbTiO3 ceramics were produced by sol-gel processing using alkoxide, which has not been reported to be successful. The PbTiO3 gels were prepared from Ti alkoxide and lead acetate without any dopants. They were calcined at $600^{\circ}C$ and miled to produce fine PbTiO3 powder. It was pressed into discs and they were sintered at 110$0^{\circ}C$ for a few hours. The sintered ceramics were relativley hard and dense as having about 96% of theoretical density of PbTiO3. Fabrication of pure PbTiO3 ceramics by sol-gel processing is possibly due to their small grain size and uniform distribution of residual stress created during cubic-tetragonal transition over large number of small grains in fine grain PbTiO3 ceramics.

• 한국세라믹학회지
• /
• 제32권1호
• /
• pp.1-10
• /
• 1995

Effects of calcination temperature on microstructure and electric-magnetic properties of Mg-ferrite were investigated. As the calcination temperature increase, the green density and the sintered density increase due to the enhancement of densification of calcined powder. The grain size in the sintered ferrite increases with increasing the calcination temperatures from 800 to 100$0^{\circ}C$, but decreases from 1000 to 120$0^{\circ}C$. The resistivity decreases with increasing the calcination temperatures from 800 to 110$0^{\circ}C$, but increases from 1100 to 120$0^{\circ}C$ due to the microstructure which consists of small, uniform grian size and pores at grain boundaries. Magnetization increases slightly due to the increasement of the sintered density while Curie temperature is almost constant regardless of calcination temperatures.

• The Korean Journal of Ceramics
• /
• 제6권1호
• /
• pp.58-63
• /
• 2000

The preparation of Y-doped $SrZrO_3$powder by ultrasonic spray pyrolysis was investigated as a representative system, in order to produce fine, single phase multicomponent oxide powders. A precursor solution containing metal nitrates, citric acid and ethylene glycol was atomized glycol was atomized with an ultrasonic spray nozzle. Gel particles formed by organic functional groups were pyrolyzed and subsequently calcined at $800^{\circ}C$ to obtain well-crystallized, single perovskite phase. Most of large particles exhibited macroscopic pores and weak agglomeration between primary particles. However, strong agglomeration was observed in the surfaces of large particles. The effect of the microstructures of these particles on size reduction to submicron particles was described.

• 한국세라믹학회지
• /
• 제26권1호
• /
• pp.109-115
• /
• 1989

The properties of the powders of ZrO2-MgO system prepared by co-precipitation method using ZrOCl2.8H2O and MgCl2.6H2O as starting materials were investigated after calcination from $600^{\circ}C$ to 120$0^{\circ}C$. The crystallization temperature of amorphous ZrO2 was increased as MgO contents increased. The crystallite size of ZrO2 was increased with increasing calcination temperature. The crystallite size of tetragonal ZrO2 calcined at 100$0^{\circ}C$ for 1hr wa about 45nm, and MgO contributed effectively to promoting stability of tetragonal Zirconia.