• Journal of Magnetics
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• v.18 no.3
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• pp.221-224
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• 2013

Electron paramagnetic resonance (EPR) spectra of $Mn^{2+}$ impurity ion in Stoichiometric $LiNbO_3$ single crystal (SLN) was investigated with an X-band EPR spectrometer in the temperature range of 3 K~296 K. The intensity of EPR spectrum of $Mn^{2+}$ ion was increased to 20 K and decreased again below 20 K as the temperature decreases. The zero-field splitting parameter D decreased as the temperature increases. It was suggested that $Mn^{2+}$ ion substitute for $Nb^{5+}$ ion instead of $Li^+$ ion. No changes for hyperfine interaction of $Mn^{2+}$ ion was obtained in the temperature range of 3 K~296 K.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.22-25
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• 2012

In this paper, we proposed a method of the resonant frequency shift of a microstrip patch antenna using $LiNbO_3$, PVDF and FR-4 substrates. We designed and analyzed from these parametars optimized using Ensemble V 7.0 of the simulation tool. We observed the resonant frequency by DC appled electric field in a microstrip patch antenna. When $LiNbO_3$ substrate were applied from -300 to 300 V/mm, we obtained the resonant frequency shift of maximum 29 MHz. The microstrip patch antenna with PVDF (poly vinylidene fluoride) substrate, we obtained the resonant frequency shift of maximum 17 MHz at frequency 6 GHz. but when Epoxy FR-4 substrates used, the resonant frequency does not changed. This results showed the resonant frequency shift without physical strains in a microstrip patch antenna.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.92-95
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• 2004

Using the Micro-Pulling Down (${\mu}$-PD), $MnO_2$ and $Tb_4O_7$ co-doped crack-free stoichiometric $LiNbO_3$ single crystals were grown in 1.0 mm diameter and 25-30 mm length for c-axis. The homogeneous distributions of $MnO_2$ and $Tb_4O_7$ concentration were confirmed by the Electron Probe Microanalysis (EPMA). Also, the infrared OH absorption band of the single crystals observed by using a Fourier Transform-Infrared Spectrophotometer (FT-IR) at room temperature and the photoluminescence spectra was measured with respect to the $MnO_2$ and $Tb_4O_7$ doping.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.284-285
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• 2000

광굴절률 현상은 optical signal processing과 홀로그램 기억소자로 널리 응용 될 수 있기 때문에 지금까지 광범위하게 연구되어져 왔다. 광굴절률 현상에서 중요한 변수는 빛이 있는 동안 drift, diffusion 과 photovoltaic current와 같은 전하 운반 메카니즘을 통해서 local charge의 재분포에 따른 공간전하장(Space-charge field, $E_{sc}$ )이다. 지금까지 single beam에 의한 공간전하장을 측정하는 방법으로 birefringenc $e^{1.2}$ 와 interference metho $d^{3}$을 이용하여 굴절률 변화를 측정함으로써 얻을 수 있었다. 그러나 이런 방법들은 공간전하장의 변화를 측정하기위해서 전기광학계수를 측정하여 얻는 간접적인 방법이고 또한 실험방법도 다소 복잡하다. 따라서 본 투고에서는 이미 발표된 광굴절률 현상시 제 2 고조파 세기(SHG)의 변화로부터 공간전하장을 간단하게 측정하는 방법을 이용하여 congruent, MgO가 4mole%, F $e_2$O가 0.1mole% 첨가된 LiNb $O_3$ 단결정의 공간전하장에 대해서 연구를 하였다. 이 방법은 전기광학물질인 LiNb $O_3$에서 SHG 위상정합조건이 dc 전기장에 의존하는 성질을 이용한 것이다. 그리고 온도가 일정할 경우 전기장의 변화에 따라 SHG의 크기가 변함을 이용하였다. (중략)

• Journal of the Korean Ceramic Society
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• v.30 no.7
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• pp.543-548
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• 1993

Stability and formation of Pb(Mg1/3Nb2/3)O3 (PMN) phase synthesized in Li2SO4-Na2SO4 molten salts have been investigated. And powder characteristics of PMN have been studied with a variation of processing parameters such as temperature, time, amount of the salts, and excess PbO. More ratio of Li2SO4 to Na2SO4 influences the percentage of perovskite phase due to the difference of the eutectic point of the salts, but does not influence the powder characteristics. The shape of PMN particles shows faceted morphology with bimodal distribution consisting with large and submicron parts. Particle size of PMN increased greatly with increasing soaking time or amount of salts rather than temperature. The addition of excess PbO resulted in round PMN crystallites without submicron particles. These results are discussed by XRD, SEM and thermal analyses.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.38-43
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• 2003

Fabrication process of strain-induced channel waveguides in $LiNbO_3$ was developed using strain-optic effect and compressional strain due to ~1.4 $\mu\textrm{m}$ surface Mo/Pt metal film. Characterization of the channel waveguides revealed a single transverse and depth mode in both TE and TM polarizations. Measurements showed total insertion loss of 6.2 and 7.7 ㏈/cm for TM and TE polarizations. respectively. Electro-optic intensity modulators with 11 mm long electrode length and 21 $\mu\textrm{m}$ electrode gap at $\lambda$ = 1.15 ${\mu}{\textrm}{m}$have been produced in $LiNbO_3$ substrates using strain-induced channel waveguides. Modulation depth of 100% at $\pi$-radian voltage of 16.1V has been demonstrated. Also, 1$\times$2 on/off power splitters at $\lambda$ = 0.63 $\mu\textrm{m}$ have been produced using strain-induced channel waveguides. On/off voltage of $\pm$ 25V has been demonstrated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.172-173
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• 2008

In this study, $0.95(K_{0.5}Na_{0.5})NbO_3$-0.05Li$(Sb_{0.8}Nb_{0.2})O_3$ + $Ag_2O$ + x wt% $MnO_2$ were investigated as a function of the amount of $MnO_2$ addition in order to improve dielectric and piezoelectric properties of Lead-free piezoelectric ceramics. With increasing the amount of $MnO_2$ addition, density and electromechanical coupling factor $(k_p)$ increased up to 0.3wt.% $MnO_2$ and decreased above 0.3wt.% $MnO_2$. At the sintering temperature of 1020 $^{\circ}C$, Electromechanical coupling factor $(k_p)$, density, dielectric constant $({\varepsilon}r)$ and mechanical quality factor $(Q_m)$ of composition ceramics with 0.4wt% $Ag_2O$ addition showed the optimal value of 0.431, 4.33 g/$cm^3$, 820 and 119, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.555-560
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• 2014

In this paper, in order to develop outstanding Pb-free composition ceramics, the $Fe_2O_3$-doped ($Na_{0.525}K_{0.443}Li_{0.037}$)($Nb_{0.883}Sb_{0.08}Ta_{0.037}$)$O_3$ + 0.3 wt% $Bi_2O_3$ + x wt% $Fe_2O_3$ (x= 0~1.0 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effect of $Fe_2O_3$-doping on their microstructure and electrical properties were investigated. XRD diffraction pattern studies confirm that $Fe_2O_3$ completely diffused into the NKL-NST lattice to form a new stable soild solution with $Fe^{3+}$ entering the $Nb^{5+}$, $Sb^{5+}$ and $Ta^{5+}$ of B-site. And, phase structure of all the ceramics exhibited pure perovskite phase and no secondary phase was found in the ceramics. The ceramics doped with 0.6 wt% $Fe_2O_3$ have the optimum values of piezoelectric constant($d_{33}$), planar piezoelectric coupling coefficient($k_p$) and mechanical quality factor($Q_m$) : $d_{33}$ = 233 [pC/N], $k_p$= 0.44, $Q_m$= 95. These results indicate that the ($Na_{0.525}K_{0.443}Li_{0.037}$)($Nb_{0.883}Sb_{0.08}Ta_{0.037}$)$O_3$ +0.3 wt% $Bi_2O_3$ + 0.6 wt% $Fe_2O_3$ ceramic is a promising candidate for lead-free piezoelectric ceramics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.40-43
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• 1996

Substrates of SAW filter are mainly single crystal such as LiNbO$_3$, LiTaO$_3$. However, fabrication of crystal is difficult and cost is very high. In this study, crystal was substituted for piezoelectric ceramics which has simple fabrication process. The same SAW filter mask was photolithographed on crystal(LiNbO$_3$) substrate and ceramic(PZT4, PZT5A and PZT8) substrate in order to compare experimental value with theoretical value. The difference of center frequency was only 3.7%. PZT8 showed good bandwidth properties. It is considered that PZT8 has higher mechanical quality factor and propagation velocity than PZT4, PTT5A.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.148-149
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• 1999