Sang-Man Park

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.

Densification and Dielectric Properties of Yb 2 O 3 doped (Ba 1 Sr 1 Ca)TiO 3 Thick Films

[ ] (BSCT) powders, prepared by sol-gel method, were mixed with organic vehicle and the BSCT thick films were fabricated by the screen printing method. The structural and dielectric properties were investigated as a function of the doping contents. As a result of the TG-DTA, exothermic peak was observed at around due to the formation of the polycrystalline perovskite phase. All BSCT thick films showed the typical XRD patterns of a cubic polycrystalline structure. The average thickness of all BSCT thick films was about . The grain size of the BSCT thick film doped with 0.7 mol% was approximately . The Curie temperature and relative dielectric constant at room temperature decreased with increasing amount. Relative dielectric constant and dielectric loss of the specimen doped with 0.1 mol% were 4637 and 19 % at Curie temperature, respectively.

Structural and Electrical Properties of (Ba,Sr,Ca)TiO 3 Thick Films doped with Dy 2 O 3

In this study, we investigated the effects of structural and electrical properties of thick films with variation contents. powders, prepared by the sol-gel method, were mixed organic vehicle. The BSCT thick films doped with 0.1, 0.3, 0.5, 0.7 mol% were fabricated by the screen-printing techniques on the alumina substrates and the structural and dielectric properties were investigated with variation of doping contents. All BSCT thick films were sintered at , for 2hr. In the TG-DTA analysis, the formation of the polycrystalline perovskite phase was observed at around . In the XRD analysis, all BSCT thick films showed the cubic perovskite structure. The average thickness of BSCT thick films was approximately . The Curie temperature decreased with increasing amount. The relative dielectric constant and dielectric loss of BSCT thick films doped with 0.1 mol% were 6267 and 2.6 %, respectively.

Characterization of PZT composite thick films fabricated using a modified Sol-Gel based process

Ferroelectric PbZr0.6Ti0.4O3 thick films were fabricated using a combination of screen-printing method and PZT precursor sol coating process. Structural and electrical properties of the PZT thick films with the treatment of sol coating were investigated. The porosity decreased and the densification increased with increasing the number of sol coatings. The thickness of all thick films was approximately 60-61 mm. The relative dielectric constant increased and dielectric loss decreased with increasing the number of sol coatings, the values of the 6-coated PZT-6 film were 167.8, 0.78 % at 1kHz, respectively. The remanent polarization and coercive field of the 6-coated PZT-6 thick films were 14.1 muC/cm2 and 20.3 kV/cm, respectively.

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.

Effect of Composition and Coating of Precursor Solution on a Micro Structural Properties of PZT Thick Films

The influence of the number of solution coatings on the densification of the PZT thick films was studied. PZT powder and PZT precursor solution was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The powder and solution of composition were (A) PZT(80/20)/PZT(20/80), (B) PZT(70/30)/PZT(30/70) and (C) PZT(60/40)/PZT(40/60), (D) PZT(52/48)/PT. The coating and drying procedure was repeated 4 times. And then the PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 moth and the number of coating was repeated from 0 to 6. The porosity of the thick films was decreased with increasing the number of coatings and the PZT thick films with 6-times coated showed the dense microstructure and thickness of about . A grain size was increased with increasing the coating number. All PZT thick films showed the typical XRD patterns of a typical perovskite polycrystalline structure. The relative dielectric constant of PZT thick films was improved 30-100% as the number of coatings.

Influence of Precursor Solution Coating Parameters on Ferroelectric Properties of Pb(Zr 0.7 Ti 0.3 )O 3 Thick Films

The influence of the concentration of precursor solution and the number of solution coatings on the densification of the (PZT) thick films was studied. PZT powder and PZT precursor solution were prepared by3 sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The composition of powder and precursor solution were PZT(70/30) and PZT(30/70), respectively. The PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 to 2.0 mol/L[M] and the number of coating was repeated from 0 to 6. The XRD patterns of all PZT thick films shelved typical perovskite polycrystalline structure. The porosity of the thick films was decreased with increasing the number of coatings and 6-time coated films with 1.5 M showed the dense microstructure and thickness of about . The relative dielectric constant of the PZT thick film was increased with increasing the number of solution coatings and the thick films with 1.5 M, 6-time coated showed the 698. The remanent polarization the 1.5 M and 6-time coated PZT thick films was .

Densification and Electrical Properties of Screen-printed PZT Thick Films

Ferroelectric (PZT(52/48)) thick films were fabricated by the screen-Printing method on the alumina substrates, and (PT) Precursor solution, which prepared by sol-gel method, was spin-coated on the PZT(52/48) thick films to obtain a densification. Its structural and electrical properties of the PZT(52/48) thick films with the treatment of PT precursor solution coating were investigated. The particle size of the thick films was increased with increasing the number of coatings and the thickness of the PZT-6 (6: number of coatings) films was about . The relative dielectric constant increased and the dielectric loss decreased with increasing the number of PT sol coatings. The relative dielectric constant and dielectric loss of the PZT-6 thick film were 475 and 2 %, respectively. The remanent polarization, coercive field and breakdown strength of the PZT-6 film were , 15 kV/cm and 60 kV/cm, respectively.

Electrical Properties of ZnO Varistors with Variation of Glass Addition

ZnO varistor ceramics were fabricated with variation of addition of glass-frit amount and the sintering temperature was . The average grain sizes were showed increased from , and varistor voltages were decreased from 506V to 460V by added amount of glass-frit. Nonlinear coefficient , of all were with increasing the amount of glass-frit more than 70, in case of added on glass-frit was 83. And leakage current were less than with applied at of varistor voltage. The clamping voltage ratio of the specimens added glass-frit was 1.41 at applied 25A . In the specimen added glass-frit, endurance of surge current and deviation of varistor voltage were , respectively and clamping voltage ratio was 2.33. In the Specimen added glass-frit were superior to any other compositions on High Temperature Load Test(HTLT) for 1000 hr at , and deviation of the varistor voltage were .

Environmental Properties of ZnO Varistors with Variation of Sintering Temperature

ZnO varistor ceramics added a glass-frit 0.03 were fabricated with variation of sintering temperature. The sintering temperature and time were and 2 h. The average grain sizes increased and the varistor voltage decreased with increasing the sintering temperature. The values of the specimen sintered at were and 329 V, respectively. The leakage current of all specimens was less than at DC of varistor voltage. The clamping voltage ratio of the specimen sintered at was 1.37. The endurance of surge current and the deviation of varistor voltage of the specimen sintered at were 6400 and , respectively. After the High Temperature Load Test(HTLT) at for 1000 h, the specimen sintered at showed the lowest deviation of varistor voltage of .