Young Hie Lee

Dielectric properties of Pb(Zr,Ti)O3 heterolayered films prepared by sol-gel method

Ferroelectric Pb(Zr,Ti)O3 (PZT) heterolayered thin films were fabricated by the alkoxide-based sol–gel method. PZT (20/80) and PZT (80/20) stock solutions were made and alternately spin-coated on the Pt/Ti/SiO2/Si substrate. Each layer was dried at 300°C for 30 min and sintered at 650°C for 1 h. The coating and heating procedure was repeated 6 times to form heterolayered films. PZT film thickness, obtained by one cycle of drying/sintering, was approximately 80 nm. The PZT heterolayered films showed dense and fine grain structures with a grain size of less than 0.2 µm. The relative dielectric constant and the dielectric loss of the 6-coated PZT heterolayered film(PZT-6) were approximately 1385 and 3.3%, respectively. As the number of coatings increased, remanent polarization increased, the coercive field decreased and the values for the PZT-6 film were 8.13 µC/cm2 and 12.5 kV/cm, respectively. The leakage current density of the PZT-6 film at 5 V was 8.8 ×10-13 A/cm2.

Preparation and Characterization of Lead Zirconate Titanate Heterolayered Thin Films on Pt/Ti/SiO2/Si Substrate by Sol–Gel Method

Ferroelectric Pb(ZrxTi1-x)O3 (PZT; x=0.2, 0.8) heterolayered thin films were fabricated by the spin-coating method on the Pt electrode alternately using PZT(20/80) and PZT(80/20) metal alkoxide solutions. All PZT heterolayered films show dense structure without the presence of the rosette structure. The lower PZT layers provide the nucleation site for the formation of a perovskite phase in the upper PZT films. Pb-deficient pyrochlore phase was formed at PZT/Pt interface due to diffusion of the Pb element into the Pt bottom electrode. The relative dielectric constant and dielectric loss of the six coated PZT heterolayered film were approximately 1385 and 3.3% at 1 kHz, respectively.

Piezoelectric Properties of Ag 2 O-doped 0.98(Na 0.5 K 0.5 )NbO 3 -0.02Li(Sb 0.17 Ta 0.83 )O 3 Ceramics

Lead-free (hereafter 0.98NKN-0.02LST) ceramics doped with were prepared using a conventional mixed oxide method. The specimen showed superior structural and electrical properties when 1 mol% was doped. For the 0.98NKN-0.02LST+1.0mol% ceramics sintered at , piezoelectric constant () of sample showed the optimum values of 207 pC/N. The 0.98NKN-0.02LST+1.0 mol% ceramics are a promising candidate for lead-free piezoelectric materials.

Structural and Electrical Properties of Vanadium Tungsten Oxide Thin Films Grown on Pt/TiO2/SiO2/Si Substrates

The V1.9W0.1O5 thin films deposited on Pt/Ti/SiO2/Si substrates by RF sputtering method exhibited fairly good TCR and dielectric properties. It was found that film crystallinity, dielectric properties, and TCR properties were strongly dependent upon the annealing temperature. The dielectric constants of the V1.9W0.1O5 thin films annealed at 300°C were 37.7, with a dielectric loss of 2.535, respectively. Also, the TCR values of the V1.9W0.1O5 thin films annealed at 300°C were about -3.7%/K.

Pyroelectric Properties of Lead Antimony Stannate-Lead Titanate-Lead Zirconate Ceramics Modified with La and Mn

In the present study, 0.10Pb(Sb1/2Sn1/2)O3-0.25PbTiO3-0.65PbZrO3 ceramics modified with La2O3 (1 mol%) and MnO2 (0~0.30 mol%) were fabricated, and the structural and pyroelectric properties with different amounts of MnO2 were studied. The crystal structure of specimens was rhombohedral, and average grain sizes decreased with increasing amounts of MnO2. The (Pb0.99La0.01)[(Sb1/2Sn1/2)0.10Ti0.25Zr0.65]O3 specimen modified with 0.24 mol% MnO2 showed a large pyroelectric coefficient, p, (=6.73×10-8 C/cm2 K) and voltage responsivity, Rv, (=125 V/W). Also, in the same specimens, noise equivalent power, NEP, and detectivity, D*, were 2.376×10-7 W/Hz1/2 and 6.793×106 cm Hz1/2 W, respectively. In the (Pb0.99La0.01)[(Sb1/2Sn1/2)0.10Ti0.25Zr0.65]O3 specimens modified with 0.24 mol% MnO2 voltage responsivity decreased with increasing chopper frequency, and was independent of the thickness of the specimens.

Electrical Properties BaTiO3 Thick Films with an Interlayer SrTiO3 Thin Films

The BaTiO3/SrTiO3 heterolayered thick films were fabricated by two different methods – thick films of BaTiO3 by screen printing method on alumina substrates electrodes with Pt, thin films of SrTiO3 by the spin-coating method on BaTiO3 thick films and once more thick films of BaTiO3 by the screen printing method on SrTiO3 layer. The leakage current and the dielectric properties were investigated for effect of various stacking sequence of sol-gel-prepared SrTiO3 layer at interface of BaTiO3 thick films. The insertion of SrTiO3 interlayer yielded BaTiO3 thick films with homogeneous and dense grain structure with the number of SrTiO3 layers. The leakage current density of the BaTiO3/SrTiO3-7 film is less that 1.5 10-9 A/cm2 at 5 V.

Dielectric Properties of Sol Infiltrated Lead Zirconate Titanate Ferroelectric Thick Films

Ferroelectric PZT(70/30) thick films were fabricated by the hybrid technique adding the sol coating process to the screen-printing process to obtain a good densification. Structural and electrical properties of the thick films with the sol concentration were investigated. The relative dielectric constant increased and dielectric loss decreased with increasing the sol concentration, the values of the thick film coated with sol concentration of 1.5 M were 698 and 2.5 % at 1 kHz, respectively. And the remanent polarization and dielectric breakdown strength of the thick film coated with sol concentration of 1.5 M were about 38 μC/cm2 and 200 kV/cm, respectively. The leakage current densities were less than 10-8 A/cm2 at the applied electric field range of 0-100 kV/cm in all thick films.

Dielectric Properties of Pb(Zr,Ti)O3 Heterolayered Thick Films Fabricated by Screen-Printing Method

Ferroelectric PZT heterolayered thick films were fabricated by the alkoxide-based sol-gel method. PZT(20/80) and PZT(80/20) paste were made and alternately screen-printed on the alumina substrates. The coating and drying procedure was repeated 4 times to form the heterolayered thick films. The thickness of the PZT heterolayered thick films was approximately 60 μm. All PZT thick films showed the typical XRD patterns of a perovskite polycrystalline structure. The relative dielectric constant and the dielectric loss of the PZT thick films sintered at 1050oC were 283 and 1.90%, respectively.

The structural properties of BaTiO/sub 3/+xNb/sub 2/O/sub 5/ ceramics

The BaTiO/sub 3/+xNb/sub 2/O/sub 5/ [x=6, 8, 10 wt%] ceramics were prepared by conventional mixed oxide method. The structural properties of the BaTiO/sub 3/+xNb/sub 2/O5 ceramics with the sintering temperature and addition of Nb/sub 2/O/sub 5/ were investigated by XRD and SEM. Increasing the sintering temperature, the 2/spl otimes/ value of BT [110] peak was shifted to the lower degree and intensity of the BN [310] peak was increased. Increasing the addition of Nb/sub 2/O/sub 5/, the intensity of BN [100] peak was decreased and BN [310], [110] peaks were increased. The grain size of the BaTiO/sub 3/+Nb/sub 2/O/sub 5/ ceramics sintered at 1500/spl deg/C were almost uniform. In the BaTiO/sub 3/+10wt%Nb/sub 2/O/sub 5/ ceramics sintered at 1450/spl deg/C, the density was 31.97 [g/cm/sup 3/].

Microwave dielectric properties of MgTiO/sub 3/-BaTiO/sub 3/ ceramics

The (1-x)MgTiO/sub 3/-xBaTiO/sub 3/(X=0.02/spl sim/0.1) ceramics were fabricated by the conventional mixed oxide method. The structural and microwave dielectric properties were investigated by the XRD, SEM, EDS and network analyzer. The sintering temperature and time were 1275/spl deg/C-1350/spl deg/C, 2 hours, respectively. In the XRD results of (1-x)MgTiO/sub 3/-xBaTiO/sub 3/ ceramics, the hexagonal BaMg/sub 6/Ti/sub 6/O/sub 19/ and ilmenite MgTiO/sub 3/ structures were coexisted. In the case of the 0.9MgTiO/sub 3/-0.1BaTiO/sub 3/ ceramics sintered at 1325/spl deg/C, dielectric constant, quality factor and temperature coefficient of resonant frequency were 32.67, 32665, -84.5 ppm//spl deg/C, respectively.