• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.10a
• /
• pp.20.2-20.2
• /
• 2011

BMNO dielectric materials with a pyrochlore structure have been chosen and they have quite high dielectric constants about 210 for the bulk material. In the case of thin films, 200-nm-thick BMNO films deposited at room temperature showed a low leakage current density of about $10^{-8}\;A/cm^2$ at 3 V and a dielectric constant of about 45 at 100 kHz. Because high dielectric constant BMNO thin films kept an amorphous phase at a high temperature above $900^{\circ}C$. High dielectric constant BMNO thin films grown at room temperature have many applications for flexible electronic devices. However, because the dielectric constant of the BMNO films deposited at room temperature is still low, percolative BMNO films (i.e., those were grown in a pure argon atmosphere) sandwiched between ultra-thin BMNO films grown in an oxygen and argon mixture have greater dielectric constants than standard BMNO films. However, they still showed a leakage problem at a high voltage application. Accordingly, a new nano-structure that uses BMNO was required to construct the films with a dielectric constant higher than that of its bulk material. The fundamental reason that the BMNO-Bi nano-composite films grown by RF-Sputtering deposition had a dielectric constant higher than that of the bulk material was addressed in the present study. Also we used the graphene as bottom electrode instead of the Cu bottom electrode. At first, we got the high leakage current density value relatively. but through this experiment, we could get improved leakage current density value.

• Journal of the Korean Ceramic Society
• /
• v.26 no.6
• /
• pp.802-810
• /
• 1989

The temperature dependence of piezoelectric strain constant and the electric field induced strain are investigated as a function of PT in 0.5[xPT-(1-x)PZ]-0.5PNN ceramics. The piezoelectric strain constant d31 has the highest value(360$\times$10-12m/V) at PT=0.68. The temperature dependence of d31 is improved as Curie temperature of sample is increased, and the electric field dependence of induced strain is decreased with the coercive field increased. This ceramic system shows both piezoelectric effect and electrostrictive effect under the applied electric field. The piezoelectric of tetragonal phase is higher than that of rhombohedral phase, and the magnitude of electrostrictive constant is appeared in the order of morphotropic, rhombohedral and tetragonal phase. The piezoelectric strain constant with applied field must be considered theelectrostrictive effect due to 90$^{\circ}$domain wall displacements, and the displacement of bimorph type actuator agrees with the calulated value well.

• Fire Science and Engineering
• /
• v.1 no.1
• /
• pp.11-18
• /
• 1987

This study is for calculating the equation of the inner temperature in the concrete, mainly by the theory or heat conduction in the solid. The results are as follow ; 1. The equation of the Fourier's heat diffusion is used formally to get the distribution of inner temperature or the concrete members, and this is programed by using the computer. 2. As study in the past, heat constant of concrete is calculated for function of temperature described recommendation heat constant value in comparison with the existing inner heating experimental result.

• Journal of the Korean Society of Tobacco Science
• /
• v.13 no.1
• /
• pp.13-18
• /
• 1991

This experiment carried out to review influence of relative humidity, temperature and net weight on cigarette hardness for the uniformal control of cigarette quality. Obtained results are as follows: 1. The difference in the cigarette physical properties of constant hardness control is considerably lower than that of constant net weight control. 2. Contribution rate for cigarette hardness is relative humidity > net weight > temperature. 3. The multiple regression equation of cigarette hardness related with relative humidity, temperature and net weight is calculated as follows.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.12
• /
• pp.101-107
• /
• 1995

To improve the leakage current, we developed two step sputtering method where PZT thin film in first deposited at room temperature followed by 600.deg. C deposition. The method used an amorphous PZT layer deposited at room temperature to keep a stable interface during sputtering at high temperature. PZT thin films were deposited on Pt/Ti/SiO$_{2}$/Si substrate at room temperature and 600.deg. C sequentially. The effect of the layer deposited at room temperature was investigated with regard to I-V characteristics and P-E hysteresis loop. In the case of the sample with the layer deposited at room temperature, both leakage current and dielectric constant were decreased. The thicker the layer deposited at room temperature was, the lower dielectric constant was. However, leakage current was indepenent of the variation of the thickness ratio. The sample with 200$\AA$ of the layer deposited at room temperature showed the most promising results in both dielectric constant and leakage current.

• Journal of Information Display
• /
• v.12 no.1
• /
• pp.23-27
• /
• 2011

The correlation between the temporal and spatial variations of the elastic constant and temperature change was examined for a light guide plate (LGP) adopted in the edge-lit light-emitting-diode backlight for mobile applications, using the micro- Brillouin light scattering method. The velocity of sound and the elastic constant $C_{11}$ of an LGP made from bisphenol-A polycarbonate (PC) were investigated as functions of temperature, time, and position on the LGP. The temporal variation of $C_{11}$ exhibited an exponential decay, while the spatial variation of $C_{11}$ reflected the temperature distribution on the LGP. The glass transition temperature of the PC LGP was found to be located at $155^{\circ}C$. The result showed that systematic transformation between the elastic property and the temperature is possible and that the temperature distribution on the bulk LGP can be accurately probed via the present experiment method, without using any special temperature measurement equipment.

• Journal of Power System Engineering
• /
• v.21 no.3
• /
• pp.12-18
• /
• 2017

Diesel and gasoline engines will be used as main power system of automobiles. Recently, engine downsizing is widely applied to both gasoline and diesel engines in order to improve fuel economy and exhaust emissions. Engine downsizing means small engine combustion chamber with higher combustion pressure. Therefore, spray and combustion process should be investigated under these high pressure and temperature conditions. In this study, constant volume combustion chamber which enables easy optical access from six directions was developed. Combustion chamber was designed to resist maximum pressure of 15 MPa and maximum temperature of 2,000 K. Combustible pre-mixed mixture was introduced into combustion chamber and ignited by spark plugs. High pressure and temperature were implemented by combustion of pre-mixed mixture. Three initial conditions of different pressure and density were tested. High repeatability of combustion process was implemented which was proven by low standard deviation of combustion pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.309-313
• /
• 1997

(Ba$_{x}$Sr$_{l-x}$)TiO$_3$(BST) thin fi1ms with various Ba/Sr ratios were deposited on Pt(80nm)/SiO$_2$(100nm)/Si by RF magnetron sputtering. BST thin films which have x=0.6, 0.5, 0.4 were studied dielectric properties with temperature variation. The frequency was used from 100Hz to 1MHz for measuring dielectric constant. The measurement conditions of dielectric constant with Temperature Variation were 1KHz and 2$0^{\circ}C$. As a result, the dielectric constant of BST thin film was about 425 and loss factor was 0.013. Also, with increasing Temperature, the dielectric constants of BST thin films were gradually decreased.sed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.989-992
• /
• 2001

(Ba$\sub$0.6-x/Sr$\sub$0.4/Ca$\sub$x/)TiO$_3$(x=0.10, 0.15, 0.20) specimens were fabricated by the solid state reaction method and then the structural and dielectric properties as a function of the composition ratio and sintering temperature were studied. The BSCT(50/40/10) specimen sintered at 1500$^{\circ}C$ showed the highest average grain size(18.25 ${\mu}$m). The Curie temperature and dielectric constant at room temperature decreased with increasing Ca content. The dielectric constant and dielectric loss of the BSCT(50/40/10) specimen, sintered at 1450$^{\circ}C$, were about 4324 and 0.972% at 1KHz, respectively. Dielectric constant at room temperature decreased with increasing an applied field, tunability of the BSCT(50/40/10) sintered at 1300$^{\circ}C$ was 18%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.611-615
• /
• 2003

The crystalline and dielectric properties on $Al_2O_3$ filled glass frit ($CaO-Al_2O_3-SiO_2-MgO-B_2O_3$) with admixtures of $TiO_2$ have been investigated. The dielectric constant value of $7.5{\sim}7.8$, quality factor value of 700 were obtained for glass frit : $Al_2O_3$ (50 : 50 wt%) ceramics. As the amount of $TiO_2$ increased, temperature coefficient of dielectric constant were decreased.