Sung-Pill Nam

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.

Dielectric and Pyroelectric Properties of Dy-doped BSCT Thick Films by Screen-printing Method

(Ba 0.57 Sr 0.33 Ca 0.10 )TiO₃ (=BSCT) powders, prepared by the sol-gel method, were doped using MnCO₃ as the acceptor and Dy₂O₃ as the donor. This powder was mixed with an organic vehicle. BSCT thick films were fabricated by the screen-printing techniques on the alumina substrate. The structural and dielectric properties of BSCT thick films were investigated with variation of the Dy₂O₃ amount. As a result of the differential thermal analysis (DTA), the exothermic peak was observed at around 670℃ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films showed the XRD patterns of a typical polycrystalline perovskite structure. The average grain size of BSCT thick films decreased with an increasing amount of Dy₂O₃. The relative dielectric constant and dielectric loss of the BSCT thick film doped Dy₂O₃ 0.1㏖% were 4637.4 and 1.6% at 1㎑, respectively.

Effect of Sintering Temperature on Structural and Dielectric Properties of (Ba 0.54 Sr 0.36 Ca 0.10 )TiO 3 Thick Films

Barium strontium calcium titanate powders were prepared with the sol-gel method. Ferroelectric (BSCT) thick films were fabricated by the screen-printing method on alumina substrate. Then we investigated the structural and dielectric properties of the BSCT thick films at different sintering temperatures. The thermal analysis showed that the BSCT polycrystalline perovskite phase formed at around . The X-ray diffraction analysis showed a cubic perovskite structure with no second phase present in all of the BSCT thick films. The average grain size and the thickness of the specimens sintered at were about and , respectively. The relative dielectric constant increased and the dielectric loss decreased as the sintering temperature was increased; for BSCT thick films sintered at the values of the dielectric constant and the dielectric loss were 5641 and 0.4%, respectively, at 1 kHz.

Electrical and Structural Properties of Lead Free 0.98 (Na 0.44 K 0.52 )Nb 0.84 O 3 -0.02Li 0.04 (Sb 0.06 Ta 0.1 )O 3 -0.5 mol%CuO Ceramics

The 0.98 ( ( mol%CuO ceramics have been fabircated by ordinary sintering technique and the effect of various calcination method on the electrical propertis and microstructure have been studied. It was observed that the various calcination method influenced the elelctrical properties and structural properties of the 0.98NKN-0.02LST-0.5 mol%CuO ceramics with the optimum piezoelectric constant () and electromechanical coupling factor () at room temperature of about and 0.349, respectively, from 0.98NKN-0.02LST-0.5 mol%CuO ceramics sample. The curie temperature () of this ceramic was found at . The 0.98NKN-0.02LST-0.5 mol%CuO ceramics are a promising lead-free piezoelectric ceramics.

Structural and Dielectric Properties of Sol-gel Derived BiFeO 3 /Pb(Zr,T)O 3 Heterolayered Thin Films

(PZT))is one of the most important electric materials for use in piezoelectric transducers such as buzzers, underwater sonar, speakers, ultrasound transducers for medical diagnostics, and actuators for precise positioning. The electrical conductivity of PZT ceramics can be controlled by minor modification of the dopants and by variation of the sintering conditions without seriously affecting the other properties. The large number of polarization directions available in PZT compositions near the morphotrophic phase boundary renders the solid solution of tetragonal PbTiO

Piezoelectric and Dielectric Properties of NKN-(1-x)BNT-xBT Ceramics

In this study, piezoelectric and dielectric properties of the [NKN-(1-x)BNT-xBT] ceramics were investigated. The lead-free NKN-(1-x)BNT-xBT ceramics were fabricated by a conventional mixed oxide method. The results indicate that the addition of significantly influences the sintering, microstructure, phase transition and electrical properties of NKN-BNT ceramics. A gradual change in the piezoelectric and dielectric properties was observed with the increase of BT contents. The dielectric constant, piezoelectric constant () and electromechanical coupling factor () increased at the morphotropic phase boundary (MPB). The

ELECTRICAL AND MECHANICAL CHARACTERISTICS OF EPOXY-NANOCLAY COMPOSITE

In this study, we investigated the effects of nanoclay additives on the electrical and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) epoxy resin. Epoxy-clay nanocomposites were synthesized using organically modified two montmorillonite clays (MMT) with different interlamellar spacing (31.5 A and 18.5 A). The electrical and mechanical properties of epoxy-clay nanocopomosites were measured with variation of the amount and type of clay. The nanocomposites were found to be homogenous materials although the nanocomposites still have clay aggregates with increasing nanoclay contents. The dielectric constant showed between 3.2 ~ 3.5 and the dielectric loss showed between 3.2 ~ 5.7% in all nanocoposites. The dielectric strength and tensile strength of the 5 wt% Cloisite 15A added epoxy-oclay nanocomposite were 23.9 kV/mm and 86.7 MPa, respectively.

Electrochemical Properties of (Li 0.5-x Na x La 0.5 )Ti 0.8 Zr 0.2 O 3 Ceramics as Improved Electrolyte Materials for Li-ion Batteries

We fabricated (Li0.5-xNaxLa0.5)Ti0.8Zr0.2O3(LNTLZ)ceramics (0≤x≤0.4) with a perovskite structure via standard solid state synthesis. The influence of Na content on the structural and electrical properties of LNTLZ ceramics was also investigated. During XRD patterns analysis, all of the samples showed orthorhombic structure. The resistance of LNTLZ ceramics decreased as Na content increased, and the maximum activation energy shows 0.56 eV at x=0.4 at room temperature. These results indicated that LNTLZ ceramics are a candidate for use Lithium ion batteries as electrolytes.

Electrical Properties of lead free (Na,K,Li)(Nb,Sb,Ta)O 3 Ceramics with MnO 2 Addition

Abstract - Electrical properties and microstructure were investigated on the effects of MnO 2 and the lead-free (Na 0.44 K 0.52 Li 0.04 )(Nb 0.83 Sb 0.07 Ta 0.1) O 3 ceramics with the addition of MnO 2 were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of MnO 2 addition. For the NKN-LST-xmol%MnO 2 sintered at 1100℃, bulk density increased with the addition of MnO 2 and showed maximum value at addition 1.0mol% of MnO 2 . Curie temperature of the NKN-LST ceramics slightly decreased with adding MnO 2 . The dielectric constant, piezoelectric constant (d 33 ) and electromechanical coupling factor (k p ) increased below 0.25mol% of MnO 2 addition, which might be due to the increase in density. The high piezoelectric properties = 145 pC/N, electromechanical coupling factor = 0.421 and dielectric constant = 2883 were obtained for the NKN-LST-0.25mol%MnO 2 sintered at 1100℃ for 4h. Key Words : Piezoelectric properties, Lead-free, NKN-LST-MnO

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.