• Advances in materials Research
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• v.2 no.2
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• pp.119-131
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• 2013

Impedance and electrical conduction studies of $Ba(Nd_{1/2}Nb_{1/2})O_3$ ceramic prepared using conventional high temperature solid-state reaction technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group $Pm\bar{3}m$. Energy dispersive X-ray analysis and scanning electron microscopy studies were carried to study the quality and purity of compound. The circuit model fittings were carried out using the impedance data to find the correlation between the response of real system and idealized model electrical circuit. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in $Ba(Nd_{1/2}Nb_{1/2})O_3$. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy.

• Journal of Sensor Science and Technology
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• v.7 no.6
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• pp.386-393
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• 1998

We have carried out the measurements of complex dielectric constants with impedance/gain-phase analyzer using capacitor method and the experiments of high temperature X-ray powder diffraction with X-ray diffractometer using ${\theta}-2{\theta}$ scan method for the KTP single crystal which has the premium nonlinear optical properties. From the results of high temperature X-ray powder diffraction experiments, we have found that KTP does not undergo structural phase transition below $900^{\circ}C$. It is clear that KTP undergoes structural phase transition around $900^{\circ}C$ and belongs to orthorhombic above $900^{\circ}C$ still. However, we have applied phenomenological relation of dielectric relaxation to the results of complex dielectric measurement and have found that relaxation mechanism of KTP well satisfies the Cole-Cole relation over the temperature range from $-78^{\circ}C$ to $200^{\circ}C$. And also the relaxation time well satisfies the Vogel-Fulcher relation. It is regarded that the hopping and thermally activated diffusion mechanism may control the conduction behavior of KTP above $200^{\circ}C$.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.44-51
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• 1999

The electrical conduction mechanism of high dielectric $(Ba,Sr)TiO_3$ (BST) thin film capacitor, which is the promising cell capacitor for high density DRAM, was investigated in low field region (<0.2MV/cm). It is known that the current in the low field region consists of dielectric relaxation current and leakage current. The current-time (I-t) measurement technique under the constant voltage was used for extracting successfully each current component. The conduction mechanism of the BST capacitor was deduced from the dependency of the current on the measurement temperature, strength of electric field, the polarity of applied electric field and post annealing process. From these results, it was suggested that the dielectric relaxation current and the leakage current are originated from the redistribution of internally trapped electron by hopping process and Pool-Frenkel conduction mechanism, respectively. It was also concluded that traps causing these two current components are due to oxygen vacancies within the BST film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.6
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• pp.475-480
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• 2001

Glasses in he system CuO-P$_2$O$_{5}$ -Nb$_2$O$_{5}$ -Nb$_2$O$_{5}$ -V$_2$O$_{5}$ were prepared by a press-quenching method on the copper plate. the glass-ceramics from these glasses were obtained by post-heat treatment, and the crystallization behavior and DC conductivities were determined. The conductivities of the glasses were range from 10$^{-6}$ s.$cm^{-1}$ / at room temperature ,but the conductivities of the glass-ceramics were 10$^{-3}$ s.$cm^{-1}$ / increased by 10$^3$ order. The crystalline product in the glass-ceramics was CuV$_2$O$_{6}$ . the crystal growth of CuV$_2$O$_{6}$ phase increased with heat-treatment conditions. The linear relationship between il($\sigma$T) and T$^{-1}$ suggested that the electrical conduction in the present glass-ceramics would be due to a small polaron hopping(SPH) mechanism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.934-937
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• 2003

Glasses in the system $CuO-P_2O_5-V_2O_5$ were prepared by a press-quenching method on the copper plate. The glass-ceramics from these glasses were obtained by post-heat treatment, and the crystallization behavior and DC conductivities were determined. The conductivities of the glasses were range from $10^{-6}s.Cm^{-1}$ at room temperature, but the conductivities of the glass-ceramics were $10^{-3}s.Cm^{-1}$ increased by $10^3$ order. The crystalline product in the glass-ceramics was $CuV_2O_6$. Heat-treatment conditions influenced the crystal growth of $CuV_2O_6$ and conductivity. The linear relationship between in (${\sigma}T$) and $T^{-1}$ suggested that the electrical conduction in the present glass-ceramics would be due to a small polaron hopping(SPH) mechanism.

• Bulletin of the Korean Chemical Society
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• v.11 no.1
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• pp.11-15
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• 1990

The temperature dependence of electrical conductivities and thermoelectric power of $I_2$-doped poly(1,4-penylene vinylene-co-2,5-dimethoxy-1,4-phenylene vinylene)s [poly(PV-co-DMPV)] and poly(1,4-phenylene vinylene-co-2,5-thienylene vinylene)s [poly(PV-co-TV)] were studied. The former copolymers were also doped with $FeCl_3$. All the samples used were in thin film forms. The temperature dependence of electrical conductivity implies that the variable range hopping conduction mechanism applises to these systems. The activation energy for the electrical conduction in dimethoxy-phenylene vinylene (DMPV) copolymers ranged from about 7 to 30 meV depending on the polymer composition and the nature of the dopant. It was significantly higher for $I_2$-doped thienylene vinylene (TV) copolymers, namely 90-200 meV. The values of the room temperature thermoelectric power were $30-70{\mu}V/K$ for DMPV copolymer and $100-800{\mu}V/K$ for TV copolymers. Anisotropy in the electrical conductivities was also studied for oriented films obtained by uniaxial stretching of the precursor polymer films.

• Bulletin of the Korean Chemical Society
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• v.17 no.4
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• pp.321-324
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• 1996

Sr1+xSm1-xFeO4-y solid solutions with a composition range 0.00 ≤x≤1.00 have been prepared at 1200 ℃ in air under normal atmospheric pressure. All the solutions exhibit the K2NiF4-type structure of tetragonal system. Mohr salt analysis shows that the mole ratio of Fe4+ ion to Fe3+ ion or the τ value increases with the x value. Nonstoichiometric chemical formulas have been formulated from the x, τ, and y values. Electrical conductivity was measured in the temperature range of 173-373 K under atmospheric air pressure. The conductivities of each sample are varied within the semiconductivity range. The conductivity at constant temperature increases steadily with x value and activation energies are varied from 0.14 to 0.32 eV. The conduction mechanism of the ferrite system may be proposed as a hopping model of conduction electrons between the mixed valence states. The Mossbauer spectrum for the composition of x=0.00 shows a six line pattern by which the existence of Fe3+(I.S.=0.32 mm/sec) can only be identified. The spectra for the compositions of x=0.50 and 1.00 presents broad single line patterns showing a mixed valence state.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.63-63
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• 2011

비정질 반도체/절연체의 직류와 교류 전도도 스펙트럼은 주파수에 대한 거듭제곱의 법칙 (power-law)을 따르는 보편성이 있음이 확인되었다. 이러한 보편성은 다양한 비정질 반도체/절연체 물질에서 공통적으로 관찰되었으며 현재까지 이 보편성의 물리학적 원인이 정확히 규명되지 않고 있다. 이 보편성을 설명하기 위한 모델로서 비정질 반도체/절연체 내의 전자/정공의 호핑 전도기구 (hopping conduction mechanism)가 제시된 바 있으며 다양한 비정질 시스템의 전도도 스펙트럼 해석에 인용되고 있다. 그러나 직.교류 전도기구 사이의 상이함에 대한 이견이 있으며 현재까지 정확히 규명된 바 없다. 본 연구에서는 비정질 GeSe 반도성 물질의 전도도 스펙트럼을 10 Hz-1 MHz 주파수 대역에서 측정하였으며 이를 위해 백금 상.하부 전극을 갖는 크로스바(crossbar)형의 금속-절연체-금속구조의 2단자 소자를 제작하였다. 측정 스펙트럼으로부터 본 연구의 GeSe 물질이 앞서 언급한 비정질 물질의 보편성에 부합함을 확인하였으며 스펙트럼 내의 직류와 교류 성분을 명확히 분리할 수 있었다. 직.교류 전도도 스펙트럼의 명확한 기구 분리를 위하여 4개의 상이한 면적을 갖는 크로스바에 대한 측정을 실시하였으며 그 결과로 직.교류 전도도의 상이한 면적 의존성을 관찰하였고 이를 근거로 직.교류 전도도가 서로 다른 전도기구에 기인함을 간접적으로 알 수 있었다. GeSe의 전도도 스펙트럼의 온도 의존성 실험을 위해 시편의 온도를 20-300 K 범위에서 변화시키며 전도도 스펙트럼을 측정하였으며 이를 통해 교류 전도도 스펙트럼 내에 상이한 두 개의 전도 기구가 혼재해있음을 규명하였다.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1709-1711
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• 2004

3,4-ethylenedioxythiophene(EDOT)을 ferric-toluenesulfonate(FTS)로 doping하여 합성하였다. 이때 다양한 유기용매를 함께 첨가하여 합성하였고, 온도에 따른 각각의 DC 전도도를 측정하였다. FTS로 dofing된 poly(3,4-ethylenedioxythiophene) (PEDOT)는 3-D variable range hopping model을 잘 따르며, alcohol류의 용매와 함께 합성한 경우는 상온의 DC 전도도가 2 S/cm로 0.4 S/cm의 reference 보다 전기전도를 증가시키는 반면, ketone류는 약 $10^{-11}$ S/cm로 전기전도를 감소시키는 경향을 보였다. 전도도의 증감과 doping level의 관계를 규명하기 위하여 X-ray 분석을 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1018-1021
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• 2001

1018-1021 The CuO-P$_2$O$_{5}$ containing P$_2$O$_{5}$ as glass-former were prepared by press-quenching method on the copper plate. By post-heat treatment of these glasses, the CuO-P$_2$O$_{5}$ -V$_2$O$_{5}$ -g1ass ceramics was obtained and the crystallization behavior and dc conductivities were investigovted. The heat-treated glass-ceramics decreased in electrical conductivity by the order of 10$^1$ compared to amorphous glass. The linear relationship between In($\sigma$T) and T$^{-1}$ indicated that electrical conduction in CuO-P$_2$O$_{5}$ -V$_2$O$_{5}$ -gass occurred by a small polaron hopping.