Seon-Gi Bae

Electrical Properties of (Bi,Y) 4 Ti 3 O 12 Thin Films Grown by RF Sputtering Method

Yttrium(Y)-substituted bismuth titanate (Bi4-xYx)Ti3O12 (x=0, 0.25, 0.5, 0.75, 1) (BYT) thin films were deposited using an RF sputtering method on the Pt/TiO2/SiO2/Si substrates. The structural properties and electrical properties of yttrium-substituted (Bi4-xYx)Ti3O12 thin films were analyzed. The remanent polarization of (Bi4-xYx)Ti3O12 films increased with increasing Y-content. The (Bi3.25Y0.75)Ti3O12 films fabricated using a top Au electrode showed saturated polarization-electric field (P-E) switching curves with a remanent polarization (Pr) of 8 μC/cm 2 and coercive field (Ec) of 53 kV/cm at an applied voltage of 7 V. The (Bi3.25Y0.75)Ti3O12 films exhibited fatigue-free behavior up to 4.5×10 11 read/write switching cycles at a frequency of 1MHz.

Polymorphic Phase Transition and Temperature Coefficient of Capacitance of Alkaline Niobate Based Ceramics

(hereafter, No excess NKN) ceramics and with excess (hereafter, Excess NKN) were fabricated by the conventional solid state sintering method, and their phase transition properties and dielectric properties were investigated. The crystalline structure of No excess NKN ceramics and Excess NKN ceramics were shown characteristics of polymorphic phase transition (hereafter, PPT), especially shift from the orthorhombic to tetragonal phase by increasing sintering temperature range from to . Also, the temperature coefficient of capacitance (hereafter, TCC) of No excess NKN ceramics and Excess NKN ceramics from to was measured to evaluate temperature stability for applications in cold regions. The TCC of No excess NKN and Excess NKN ceramics showed positive TCC characteristics at a temperature range from to . Especially, Excess NKN showed a smaller TCC gradient than those of Excess NKN ceramics in range from to . Therefore, NKN piezoelectric ceramics combined with temperature compensated capacitor having negative temperature characteristics is desired for usage in cold regions.

Effect of Particle Size on the Dielectric and Piezoelectric Properties of 0.95(K 0.5 Na 0.5 )NbO 3 -0.05BaTiO 3 Lead-free Piezoelectric Ceramics

The particle sizes of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 powder were controlled by secondary milling time after calcination. The average particle sizes, Dmean, of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 powders were critically changed from 14.31 μm to 0.91 μm by secondary milling time. The dielectric and piezoelectric properties of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 ceramics depended on the particle sizes of powders after calcination and the secondary milling process. As secondary milling times after calcination were increased to more than 48 hr, the dielectric and piezoelectric properties of 0.95(K0.5Na0.5)NbO3-0.05BaTiO3 ceramics were deteriorated.

ELECTRICAL PROPERTIES OF HETEROLAYERED BaTiO3/(Bi1/2Na1/2)TiO3 THICK FILMS

The heterolayered BT/BNT thick films were fabricated by screen printing techniques on alumina substrates electrodes with Pt. Their structure and ferroelectric properties were investigated with the heterolayered tetragonal/rhombohedral structure composed of the BT and the BNT thick films. The structural and electrical properties of the heterolayered BT/BNT thick films were studied. The dielectric properties such as dielectric constant, loss and remanent polarization of the heterolayered BT/BNT thick films were superior to those of single composition BNT, and those values for the heterolayered BT/BNT thick films were 1455, 0.025 and 12.63 µC/cm2.

Piezoelectric Properties and Sintering of PCW-PNN-PZT+0.5 wt%MnO 2 Ceramics

In this thesis, piezoelectric properties and sintering properties of PCW-PNN-PZT+0.5 wt% ceramics adding after creating the specimens with a general method. The lattice constant from the analysis of crystal structure showed that the crystal structure of ceramic features both rhombohdral and tetragonal structures and that the pychlore structure was decreased with the increase of the sintering temperature. The electromechanical coupling coefficient showed its maximum of 31 % in the sintered specimens at , and its minimum of 20 % in the sintered specimens at . The mechanical quality coefficient marked the maximum of 139 at the sintering temperature of .

Structural and Electrical Properties of Pb(Zr 0.4 Ti 0.6 O 3 /PbZr 0.6 Ti 0.4 )O 3 Heterolayered Thick Films

[ ] paste were made and alternately screen-printed on the substrates. We have introduced a press-treatment to obtain a good densification of screen printed films. The porosity of the thick films was decreased with increasing the applied pressure and the thick films pressed at 60 MPa showed the dense microstructure and thickness of about . The remanent polarization and coercive field increased with increasing applied pressure and the values for the PZT thick films pressed at 60 MPa were and 78.09 kV/cm, respectively.

Microwave Dielectric Properties of the 0.7Mg 4 Ta 2 O 9 -0.3SrTiO 3 Ceramics with Sintering Temperature

The structural and microwave dielectric properties of ceramics with sintering temperature were investigated. All the sample of the ceramics were prepared by conventional miked oxide method and the sintering temperature was . The hexagonal phase of and the cubic phase of were coexisted. The porosity of ceramics were reduced with increasing sintering temperature. In the case of ceramics sintered at , dielectric constant, quality factor and temperature coefficient of resonant frequency were 14.51, 82,596 GHz and , respectively.

Microwave dielectric properties of (Bi/sub 0.95/Sb/sub 0.05/)NbO/sub 4/ ceramics with sintering temperature

The Bi/sub 0.95/Sb/sub 0.05/NbO/sub 4/ ceramics with dopant(0.2wt%/spl sim/0.3wt%CuO) were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature by XRD. Also the microwave dielectric properties of the Bi/sub 0.95/Sb/sub 0.05/NbO/sub 4/ ceramics were studied. According to the X-ray diffraction patterns of the Bi/sub 0.95/Sb/sub 0.05/NbO/sub 4/ ceramics with CuO, the structure of the ceramics had the orthorhombic. The dielectric constant, quality factor and temperature coefficient of resonant frequency of the Bi/sub 0.95/Sb/sub 0.05/NbO/sub 4/+CuO(0.3wt%) ceramics sintered at 975/spl deg/C, were 39.2, 9,730 and -3.2 ppm//spl deg/C, respectively. The dielectric constant, quality factor and temperature coefficient of resonant frequency of the Bi/sub 0.95/Sb/sub 0.05/NbO/sub 4/+CuO(0.5wt%) ceramics sintered at 950/spl deg/C, were 40.5, 9,580 and -9.8 ppm//spl deg/C, respectively.

Microwave dielectric properties of BaTi/sub 4/O/sub 9/ ceramics with addition of dopant(CoO, Y/sub 2/O/sub 3/)

The BaTi/sub 4/O/sub 9/ ceramics with addition of CoO, Y/sub 2/O/sub 3/ were prepared by conventional mixed oxide method. The structural properties were investigated with sintering temperature by XRD. Also the microwave dielectric properties of the BaTi/sub 4/O/sub 9/ ceramics were studied. According to the X-ray diffraction patterns of the BaTi/sub 4/O/sub 9/ ceramics with CoO and Y/sub 2/O/sub 3/, the structure of the ceramics was orthorhombic. The dielectric constant, quality factor and temperature coefficient of resonant frequency of the BaTi/sub 4/O/sub 9/+CoO(0.5wt%) ceramics sintered at 1350/spl deg/C, were 40.8, 39,680 and 2.5 ppm//spl deg/C, respectively. The dielectric constant, quality factor and temperature coefficient of resonant frequency of the BaTi/sub 4/O/sub 9/+Y/sub 2/O/sub 3/(0.5wt%) ceramics sintered at 1400/spl deg/C, were 41.3, 40,900 and 3.2 ppm//spl deg/C, respectively.

A study on the properties and fabrication of BaTiO/sub 3/ thin films by the RF sputtering

BaTiO/sub 3/ thin films were prepared on Pt(100)/SiO/sub 2//Si(100) substrates by RF sputtering, whose structural, crystallographic, and electrical properties were examined according to the deposition conditions and annealing temperatures. The optimal Ar/O/sub 2/ gas flow rate, sputtering pressure, RF power and annealing temperature were 4/1, 12[mTorr], 120[W] and 650[/spl deg/C] for 1[hr], respectively. From the results of X-ray diffraction (XRD) and D-E hysteresis characteristics, BaTiO/sub 3/ thin films deposited at the optimal conditions showed a ferroelectric phase. The growth rate of deposited film was about 0.75[/spl Aring//sec], and the dielectric constant and dielectric loss were about 683 and 0.05, respectively.