Byung Moon Jin

Piezoelectric properties and equivalent circuits of ferroelectric relaxor single crystals

Temperature dependent piezoelectric properties of ferroelectric relaxor single crystals, particularly the cerium-doped strontium barium niobate compositions (SBN60: Ce), were investigated by resonance and anti-resonance technique. Characteristic resonant frequencies (fr−fa, fs−fp, and fm−fn) were studied using equivalent circuit simulation. Piezoelectric resonance in a relaxor resonator persists into temperatures much higher than Tm (the temperature at which dielectric constant, κ, has a maximum at 1 kHz) in comparison with the normal ferroelectrics such as TGS. The parameters in an equivalent circuit, however, are phenomenally different from a normal resonator like a TGS, near and above the transition temperature region. The significance and understanding of the piezoelectric resonance characteristics in ferroelectric relaxor are discussed.

An advanced ferroelectric properties of the Mn doped Na0.5Bi4.5Ti4O15 ceramics fabricated by hot-forging method

Mn doped Na0.5Bi4.5Ti4O15 (NBTM) ceramics were fabricated by ordinary firing (OF) and hot forging (HF) method. The HF(//) sample is strongly oriented to the c-axis which is confirmed by the X-ray diffraction. Dielectric constant of HF(⊥) sample at Curie temperature is about 5176 which is larger than that (416) of the HF(//) sample. The value of the remnant polarization Pr and coercive field Ecof HF(⊥) samples at 200°C are 17.8 μC/cm2 and 28.5 kV/cm, respectively. From the temperature dependence of conductivity, the activation energy of the HF(⊥) sample is 1.65 eV in the temperature range of 520°C ∼750°C.

Universal response of dielectric behavior of single crystal TGS

Abstract Triglycine sulfate (TGS) single crystal is studied in audio frequency range to investigate its ferroelectric contribution. Audio frequency characteristics of TGS shows universal dynamic response: and its characteristic exponent n has its minimum at the transition temperature. This fact is in contrast with Jonschers results, and we imply that this is because at the transition point, the crystals restoring force is minimum so its critical exponent should have a minimum at the transition temperature.

Dielectric response of Li0.4K0.6NbO3 crystal in the frequency domain

Complex impedance and dielectric constants of ferroelectric crystals Li0.4K0.6NbO3 have been studied in the frequency domain at several temperatures. A strong low-frequency dielectric dispersion below 1 kHz was revealed in the high temperature range. The normalized behaviour of the complex dielectric constants satisfies the universal dynamic response with its power exponent n=0.04. In the high frequency region, the complex impedance was described by a modified Cole-Cole arc. An equivalent circuit for the transport process of high frequency region has been examined. The temperature-dependent exponent has its minimum at the ferro- to para-electric phase transition point and relaxation frequencies do not satisfy the Arrhenius law in the ferroelectric region

Vanadium Doping Effects on Ferroelectric and Electrical Properties of Bi-Excess Bi3.25 +xLa0.75Ti2.97V0.03O12 Ceramics

Bimuth(Bi) excessed and vanadium(V)-doped Bi3.25 +xLa0.75Ti2.97V0.03O12 (BLTV) ceramics were prepared by a solid state reaction. Crystallized single-phases with Bi-layered perovskite structure were confirmed by X-ray diffraction. The low frequency dielectric dispersion was decreased, and the conductivity was decreased for the Bi-excessed BLTV ceramics of x = 0.05–0.10. The V doping improved the ferroelectric properties and decreased the conductivity. The effects of V-doping on ferroelectric and electrical properties on Bi-excessed BLTV ceramics were investigated.

Preparation and structure of PbZrO3 films by KrF pulsed laser deposition

Abstract PbZrO3(PZ) thin films crystallization by rapid thermal annealing (RTA) was studied using Raman-scattering spectroscopy, and the results were compared with those of x-ray diffraction(XRD) result. It was found to be strongly affected the kinetics of subsequent amorphous-perovskite crystallization by RTA temperature. The use of such post anneals allowed to make films of reproducible microstructure and texture [both (221) and (240)] prepared by RTA. The low frequency (<200 cm−1) Raman peaks for the PZ film disappear and three new Raman peaks occur at the 83 cm−1, 138 cm−1, 273 cm−1 respectively.