Yeon Jung Kim

Effect of La2O3 modified on pyroelectric properties of 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 solid solutions

The pyroelectric and polarization properties of La2O3 modified 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 solid solution systems were examined by the static technique as a function of temperature. The peak temperature of the pyroelectric coefficient maxima was decreased by La2O3. From the pyroelectric data, two major anomalies corresponding to the rhombohedral → tetragonal → cubic phase transitions were observed. This suggests that the successive transition of 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 systems appeared not to be affected by La2O3. The optimum conditions for obtaining compositions with improved pyroelectric properties (p }~ 0.013 C/m2K at 126°C, Ps }~ 0.197 C/m2 at 25°C) are a sintering temperature of 1250°C and the nominal addition of 0.03 wt. % La2O3. The figures of merit (Fv }~ 0.034 m2/C, Fd }~ 0.357 × 10−4 Pa1/2) of the composition 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3-0.03 wt. % La2O3 are comparable to that of TGS and LiTaO3. Also, the piezoelectric constant (d33) and the electromechanical coupling factor (kp) were found to be about 379–422 × 10−12 C/N and 0.274–0.342 for 0.69PMN-0.31PT-xLa systems, respectively.

Relaxation Characteristic of the Disordered Lead Scandium Niobate

The correlation between admittance and dielectric spectroscopy of dielectric relaxation in lead scandium noibate, have been investigated. Lead scandium niobate, with composition PbSc 0.5 Nb 0.5 O₃, was prepared by conventional solid state synthesis. Conductance Y’(G), susceptance Y”(B) and capacitance C of lead scandium niobate as a function of frequency and temperature were measured. From the temperature-dependence of RLC circuit, insight into physical significance of the dielectric properties of lead scandium niobate is obtained. The relative strong frequency dependent of dielectric properties in lead scandium niobate is observed, and the phase transition occurred at a broad temperature region. Also, the value of critical exponent γ=1.6 showed on heating process. The long relaxation times part enlarged diffuse by conductivity effects with increasing temperature, and the ordering between Sc 3+ and Nb 5+ in PSN influences complex admittance and dielectric properties. Confirmed the typical characteristic of lead-type relaxor in the Raman spectra of lead scandium niobate and major ranges are between 400 and 900 cm -1 .

Stabilization of the Perovskite Phase and Electrical Properties of Ferroelectrics in the Pb₂(Sc,Nb)O 6 System

Ferroelectric Pb₂(Sc,Nb)O 6 were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were 1350℃ for 25 minutes and 1400℃ for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the Pb₂(Sc,Nb)O 6 compositions Pyrochlore phase showed about 2% in all Pb₂(Sc,Nb)O 6 specimens. It expands the growth of crystals in samples sintered at 1400℃ than 1350℃, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at 1350℃ and 1400℃ were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in Pb₂(Sc,Nb)O 6 compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.

Pyroelectricity of Ni-doped PMNT Ferroelectric for Pyroelectric Detector

A pyroelctric properties of Ni(x)-doped PMNT systems were analyzed. Modified PMNT samples were prepared using the columbite structure method. Pyroelectric current, polarization, dielectric constant and dissipation factor of Ni-doped PMNT samples were measured as a function of temperature. By adding a small amount of NiO, pyroelectricity of PMNT is increased. Unlike the normal ABO3 ferroelectric, Ni-doped PMNT showed properties for relaxor ferroelectric of causing the successive phase transition over a wide temperature. The optimum conditions for obtaining compositions with improvement ferroelectric properties are a nominal addition of 0.02 mole% Ni. Also, Nidoped PMNT ferroelectric showed excellent pyroelectric figures of merit in the vicinity of room temperature. The pyroelectric coefficient (0.00524 C/㎡K at 25℃) and figures of merit (F v ~0.039 ㎡/C and F d ~0.664×10 −4 Pa −1/2 ) of composition PMNT with 0.02 mole% Ni are comparable to the earlier reports on lead-type pyroelectrics.

Phase Transition and Relaxor Behaviors in the Lead Magnesium Niobate-based Ferroelectrics

Dielectric and pyroelectric properties of relaxor ferroelectric in the PMN-PT solid solution series have been investigated. Features of the diffuse phase transition in PMN-PT system, typical relaxor ferroelectric materials, were studied as a function of temperature and frequency. The transition temperature of the ceramics with PT~0.325 did not depend on the measuring frequency. This can best realized in a relatively random environment that apparently is provided by PMN-rich complex perovskites, including those containing Pb. The composition with PT＞0.35 show the characteristics of a normal single phase ferroelectric material. Thus the studies revealed that the morphotropic phase boundary in the PMN-PT system is in the vicinity of PT~0.3 and it has a small curvature and as a result the compositions near the morphotropic phase boundary show two phase transitions, rhombohedral→tetragonal→cubic, when the samples are heated up to higher temperature. The best optimum compositions are observed near the morphotropic phase boundary.

Minnesota Multiphasic Personality Inventory Characteristics of Parricide Offenders with Schizophrenia in Korea

Objective This study aims to examine the personality characteristics in parricide offenders, by using the Minnesota Multiphasic Personality Inventory (MMPI) test, which is commonly used in clinical medicine. Methods A total of 73 parricide offenders with schizophrenia who were admitted to National Forensic Hospital in Gongju city between September 2014 and February 2015, and 104 comparison schizophrenia patients who had been admitted to Dankook University Hospital in Cheonan city the same hospital, completed the Korean version of the MMPI. Results The parricide offender group showed significantly higher on L, F, Hs, Hy and Pd than the comparison group. The result of the regression analysis indicated that Pd and Si significantly increased the odd ratio of the sexual offender group by 2.77 times and 0.32 times, respectively (p=0.029 and p=0.023). The offenders of parricide may have developed the following characteristics: hypochondriasis, hysteria and psychopathic deviate. Conclusion These results suggested that the psychopatholgy in the offenders of parricide might be different, compared to the control group.

Erratum to: Branch length similarity entropy-based descriptors for shape representation (Journal of the Korean Physical Society, (2017), 71, 10, (727-732), 10.3938/jkps.71.593)

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Improvement of the Figure of Merit in Pb[(Mg 1/3 Ta 2/3 ) 0.7 Ti 0.3 ]O 3 Systems

The Pb[(Mg 1/3 Ta 2/3 ) 0.7 Ti 0.3 ]O₃+xwt%PbO systems at temperature of 1250℃ for 4 hours was successful synthesized. In this study, PbO-doped Pb[(Mg 1/3 Ta 2/3 ) 0.7 Ti 0.3 ]O₃ systems with non-linear behaviors showed ordering-degree dependence at the low temperature range were prepared using the columbite precursor method. And the characteristic of remnant polarization vs. electric field were analyzed. The pyroelectric, dielectric and piezoelectric properties of partially disordered Pb[(Mg 1/3 Ta 2/3 ) 0.7 Ti 0.3 ]O₃+xwt%PbO solid solutions were studied as a function of temperature, frequency, and electric field. It showed distinct features of temperature dependent of pyroelectric coefficient, spontaneous polarization and dielectric constant at about 50℃. The figure of merit was calculated as pyroelectric coefficient, dielectric constant and dissipation factor. It was found that the high voltage responsivity F V , high detectivity F D were 0.0373 ㎡/C and 0.6735×10 −4 Pa −1/2 , respectively, in the Pb[(Mg 1/3 Ta 2/3 ) 0.7 Ti 0.3 ]O₃+3.0 wt%PbO system.

Dielectric Characteristics of PbSc 1/2 Nb 1/2 O₃ Prepared by Using the One-step Solid State Reaction

The PbSc 1/2 Nb 1/2 O₃ ceramics at a relatively low temperature of 1300℃ was successful synthesized. Solid state reaction of two-step process is not necessary. The dielectric constant, dielectric loss and admittance of ceramic samples were determined. The pyroelectric characteristics are in good agreement with the dielectric properties. Ferroelectric properties of well-formed the PbSc 1/2 Nb 1/2 O₃ ceramics are in agreement with broad distribution of relaxation phenomenon. Relatively strong frequency dependent of dielectric constant is observed at about 110℃. The distinct thermal hysteresis was observed in the measurement of the dielectric constant and dielectric loss. The critical exponents of during cooling and heating measurements in the PbSc 1/2 Nb 1/2 O₃ ceramics were 1.14 and 1.59 at 1 ㎑, respectively.

Dielectric and pyroelectric properties in the La-doped 0.45Pb(Mg/sub 1/3/Ta/sub 2/3/)O/sub 3/-0.55PbZrO/sub 3/ system

Dielectric and pyroelectric properties of relaxor ferroelectric in the 0.45(Pb/sub 1-3x/2/La/sub x/)(Mg/sub 1/3/Ta/sub 2/3/)O/sub 3/-0.55PbZrO/sub 3/ solid solution series have been investigated. The dielectric constant and loss of ceramic samples were determined. The pyroelectric coefficient and spontaneous polarization were measured by the static Byer-Roundy method as a function of temperature and for various compositions in the La-doped PMT-PZ system. The addition of La/sub 2/O/sub 3/ was less effective in grain growth and shifting of the T/sub c//spl sim/12/spl deg/C/mole% downward in PMT-PZ system. Dielectric and pyroelectric properties of this system were improved by adding a small amount of La/sub 2/O/sub 3/. Compositions near 0.45PMT-0.55 PZ-0.04La have been identified to have high pyroelectric figures of merit near room temperature.