• Proceedings of the Korean Ceranic Society Conference
• /
• 2000.10a
• /
• pp.84.1-84
• /
• 2000

• Proceedings of the KIEE Conference
• /
• 1987.07a
• /
• pp.385-388
• /
• 1987

• Journal of the Korean Ceramic Society
• /
• v.27 no.6
• /
• pp.713-720
• /
• 1990

The effects of substituting Zn+2 for Ni+2 ion on dielectric and piezoelectric prooperties of Pb(Zn1/3Nb2/3)O3-Pb(Ni1/3Nb2/3)O3-PZT ceramics were investigated. With increasing Zn2+ contents the tetragonality was appreciably enhanced and the grain size decreased. Both Curie temperature and thermal stability were increased with increase in Zn2+ contents since the Zn+2 partial substition for Ni+2 could form solid solution in almost range of the composition investigated. Piezoelectric prooperties showed the maximum($\varepsilon$ T/$\varepsilon$0=5014, kp=0.56, d31=250$\times$10-12m/V) in 4.5Pb(Zn1//3Nb2/3)O3-40.5Pb(Ni1/3Nb2/3)O3-55PZT composition sintered at 125$0^{\circ}C$ and then decreased again due to the phase boundary movement for tetragonal phase of the solid solution of Zn2+ amount.

• Journal of Sensor Science and Technology
• /
• v.11 no.1
• /
• pp.60-65
• /
• 2002

$ZnGa_2O_4$ thin film phosphors have been deposited using a pulsed laser deposition method on Si(100) substrates at a substrate temperature of $550^{\circ}C$ with oxygen pressures of 100mTorr, and subsequently to investigate their photoluminescence characteristics after post-annealed at $600^{\circ}C$ and $700^{\circ}C$. As a result for X-ray diffraction, $Ga_2O_3$ shape appeared with increasing annealing temperature. The luminescent spectra show a broad band extending from 350 to 600nm peaking at 460nm. A post-annealing treatment of $ZnGa_2O_4$ thin films led to the different shape of luminescent intensity and grain size.

• Journal of the Korean Society for Heat Treatment
• /
• v.26 no.3
• /
• pp.113-119
• /
• 2013

Grain growth behaviors of hot-rolled AZ31 (Mg-3%Al-1%Zn) and AZ31-0.3%CaO alloys at elevated temperatures have been investigated in order to clarify the effect of CaO addition on grain stability of Mg-Al-based wrought alloy. The grain size of CaO-free alloy increased steeply from 673 K with an increase in annealing temperature from 573 to 773 K, whereas the grains of CaO-containing alloy were relatively stable up to 723 K. The activation energies for grain growth ($E_g$) were 12.2 and 18.3 kJ/mole between 573 and 673 K and 119.2 and 126.9 kJ/mole between 673 and 773 K in the AZ31 and AZ31-0.3%CaO alloys, respectively. This result indicates that grains in the CaO-added alloy possess higher thermal stability than CaO-free alloy. SEM observations on the annealed alloy samples revealed that higher grain stability resulting from CaO addition would be associated with the suppression of grain growth by Ca-related precipitate particles distributed in the microstructure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.22-22
• /
• 2010

0.1~5.0 at% CuO doped ZnO specimens were fabricated by a commercial ceramic process and sintered at 900~$1200^{\circ}C$ for 3h in air. The relative densities were over 97% for all samples and average grain size increased with CuO doping. The defect trap levels i.e. ionization energies of defects were increased linearly with CuO contents as 0.2 eV to 0.7 eV by using admittance spectroscopy and dielectric functions. The apparent activation energies of grain boundaries were varied but in the range of 0.96~1.1 eV. Dielectric constant were increased with CuO contents and sintering temperatures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.3
• /
• pp.165-169
• /
• 2015

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties ($d_{33}=422pC/N$, $d_{31}=161pC/N$, ${\varepsilon}_r=1,905$, $k_p=0.55$, $Q_m=160$) were obtained.

• Journal of the Korean Ceramic Society
• /
• v.26 no.4
• /
• pp.487-492
• /
• 1989

The microstructure and electrical properties of ZnO-Bi2O3 system with Bi2O3(0.5~5mol%) content have been investigated in relatin to sintering temperature and atmosphere. The grain size of ZnO increases sharply with Bi2O3(0.5~5mol%) content, but over 0.5mol% Bi2O3 increased less rapidly when sintered at 120$0^{\circ}C$. Electrical characteristics varied with sintering atmosphere and air-sintered conditions showed comparatively lower nonlinear exponents than the double-crucible conditions. Calculated barrier voltage was about 1.7V.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.6
• /
• pp.538-548
• /
• 2003

We studied effects by Re$_2$O$_3$(R=Dy, Gd, Ho) addition on the properties of Mn-Zn ferrite. The doping concentration range from 0.05 wt% to 0.25 wt%. All samples were prepared by standard fabrication of ceramics. With increasing the rare earth oxides, specific density and initial permeability increased on the whole. But, the tendencies such as upper result had the measured value on limitation and characteristics saturated or decreased properties after that. In case of excessive addition of additive beyond some level, initial permeability properties of ferrite have gone down in spite of anomalous grain. With increasing the content of additive, both the real and imaginary component of complex permeability and the magnetic loss (tan$\delta$) increased. Because the increased rate of real component had higher than imaginary component, magnetic loss increased none the less for increasing the real component related with magnetic permeability. But, the magnetic loss of ferrite doped with the rare earth oxides was lower than that of Mn-Zn ferrite at any rate. The small amount of present rare earth oxides in Mn-Zn ferrite composition led to enhancement of resistivity in bulk, and more so in the grain boundary. It was seem to be due to the formation of mutual reaction such as between iron ions and rare earth element ions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.505-509
• /
• 1997

Praseodymium-based ZnO varistor containing 2.0mol% and 4.0mol% $Y_2$O$_3$ were fabricated, respectively and its microstructure and electrical properties were investigated. Yttrium distributed nearly in the grain boundaries and cluster phase at nodal point but more in cluster phase. The average grain size of the 2.0%mol% and 4.0mol% $Y_2$O$_3$-added samples was 14.8${\mu}{\textrm}{m}$ and 8.6${\mu}{\textrm}{m}$, respectively. Compared to 2.0mol% $Y_2$O$_3$, 4.0mol% $Y_2$O$_3$-added varistors showed very good I-V characteristics exhibiting highly nonlinear exponent(87.4) and low leakage current(46.7nA). These results are the important experimental fact in this paper.