• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.242-245
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• 2000

The electrical properties of ZPCCE (ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Er$_2$O$_3$) based varistors were investigated with sintering temperature in range of 1335 to 135$0^{\circ}C$ for 1h. As the sintering temperature increases, the nonlinear exponent decreased, but was high beyond 40 except for 1.0 mol% Er$_2$O$_3$. Among all ZPCCE varistors, the varistor having the highest nonlinear exponent was obtained by sintering at 1335$^{\circ}C$, containing 2.0 mol% Er$_2$O$_3$ and then the nonlinear exponent was 78.05, and the varistors with 0.5 mol% Er$_2$O$_3$ exhibited the lowest leakage current of 1.92 $\mu$A.A.A.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.362-369
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• 2001

The electrical properties of varistors consisting of Zn-Pr-Co-Cr-Er oxides were investigated in the Er$_2$O$_3$content range of 0.0 to 2.0 mol%. the varistors without Er$_2$O$_3$ exhibited a relatively low nonlinearity, which was 14.24 in the nonlinear exponent and 21.47 $\mu$A in the leakage current. However, the varistors with Er$_2$O$_3$ sintered at 1335$^{\circ}C$ for 1h exhibited very high nonlinear exponent of 70, in particular, reaching a maximum value of 78.05 in 2.0 mol% Er$_2$O$_3$, and those sintered at 1335$^{\circ}C$ for 2h exhibited the nonlinear exponent close to 50, in particular, reaching a maximum value of52.76 in 0.5 mol% Er$_2$O$_3$. The others except for 0.5 mol% Er$_2$O$_3$-added varistors exhibited very high instability resulting in a thermal runaway within a short time, even a weak DC stress. Increasing soaking time decreased the nonlinearity, but increased the stability. The varistors containing 0.5mol% Er$_2$O$_3$ sintered for 2h exhibited excellent stability, in which the variation rate of the varistor voltage and nonlinear exponent was -1.70% and -7.15%, respectively, under more severe DC stress such as (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$/115$^{\circ}C$/12h)+(0.90 V$_{1mA}$/12$0^{\circ}C$/12h)+(0.95 V$_{1mA}$/1$25^{\circ}C$/12h)+(0.95 V$_{1mA}$/15$0^{\circ}C$/12h).TEX>/12h).

• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.605-609
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• 2004

The microstructure, electrical and dielectric characteristics of ZnO varistors were investigated at various metal oxide (NiO, MgO, and Cr$_2$O$_3$) additives. The average grain size was increased with addition of NiO while that was decreased with addition of Cr$_2$O$_3$-Thereby, the varistor voltage was higher in Cr$_2$O$_3$-added composition. Among varistors, the varistor added with Cr$_2$O$_3$ exhibited the highest nonlinearity, with 40.5 in the nonlinear exponent and 2.7 ${\mu}$A in the leakage current and its dielectric dissipation factor was relatively low value of 0.0589.

• Journal of the Korean Ceramic Society
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• v.51 no.6
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• pp.612-617
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• 2014

The microstructure, nonlinear properties, and impulse clamping characteristics of Pr/Co/Cr/Al co-doped zinc oxide ceramics were investigated with various contents of $Er_2O_3$. Increasing $Er_2O_3$ content increased the density of the sintered pellets from 5.69 to $5.83g/cm^3$, and decreased the average grain size from 10.6 to $6.5{\mu}m$. With increased $Er_2O_3$ content, the breakdown field increased from 2318 to 4205 V/cm, and the nonlinear coefficient increased from 19.4 to 40.2. The clamp characteristics were improved with the increase of the content of $Er_2O_3$. The varistors doped with 2.0 mol% exhibited the best clamp characteristics, in which the clamp voltage ratio was 1.40-1.73 at 1-50 A in an impulse current.

• Journal of the Korean Ceramic Society
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• v.37 no.12
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• pp.1159-1164
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• 2000

페롭스카이트 구조를 갖는 E $r_{1-x}$S $r_{x}$Cr $O_{3-y}$ 계에서 x=0.0, 0.05, 0.1, 0.2인 비화학양론적 화합물 고용체를 1573 K 대기압 하에서 제조하였다. X-선 회절분석을 통하여 제조된 모든 계들이 등방정계 단일상을 형성하였고, 또한 반지름이 큰 S $r^{2+}$를 doping 시켜줌에 따라 격자상수 및 환산부피가 증가됨을 알 수 있었으며, 단위 세포의 부피는 직선성을 보이며 증가하였다. TG-DTA에 따른 열분석 결과 Sr이 치환되지 않은 계에서는 상전이가 발생하는 반면, x값이 0.05 이상인 계들은 고온영역에 이르기까지 등방정계에서 마름모정계로의 상전이가 억제되었다. 전자현미경을 통하여 치환된 Sr의 몰비에 따른 시료들이 미세구조를 관찰하였고, d.c 전도도 측정을 통하여 다결정성 시료계들이 가지는 전도도의 온도 의존성으로부터 구한 활성화 에너지는 0.17 eV였다.다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.335-335
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• 2008

Phosphate glass samples with various $Cr_2O_3$ and $Er_2O_3$ contents based upon $55P_2O_5\cdot24BaO\cdot10K_2O\cdot4Al_2O_3\cdot6Yb_2O_3$ were prepared. The prepared glass compositions are dehydrated using gas bubble flow method in open system and investigated the effects of the eliminating of OH groups from the glass melts with bubbling time. It was found that the probability of $Er^{+3}$ fluorescence quenching by OH groups oscillations linear depends upon the OH groups absorption coefficients in the maximum of the stretch vibrations band at $3500cm^{-1}$ while $Er^{+3}$ concentration range is between $1.6\times10^{19}$ and $21.2\times10^{19}$ ion/$cm^3$.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.216-221
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• 2010

The microstructure, electrical properties, and DC-accelerated aging behavior of the Zn-Pr-Co-Cr-Y-Er (ZPCC-YE) varistors were investigated for different amounts of erbium oxide ($Er_2O_3$). The microstructure consisted of zinc oxide grain and an intergranular layer ($Pr_6O_{11}$, $Y_2O_3$, and $Er_2O_3$-rich phase) as a secondary phase. The increase of $Er_2O_3$ amount decreased the average grain size and increased the sintered density. As the $Er_2O_3$ amount increased, the breakdown field increased from 5094 V/cm to 6966 V/cm and the nonlinear coefficient increased from 27.8 to 45.1. The ZPCC-YE varistors added with 0.5 to 1.0 mol% $Er_2O_3$ are appropriate for high voltage, with high nonlinearity and stability against DC-accelerated aging stress.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.161-164
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• 1998

Erbium doped garnet crystals were grown by Czochralski method. Relationshipes between crystal quality and crystal growth factors such as pulling rate, rotation rate and concentration of active ions and sensitizers were investigated. Optimum pulling and rotation rate for high quality Er:YAG crystal were 1 mm/hr and 20 rpm and for Er,Cr:YSGG crystal 2-4 mm/hr and 10 rpm respectively. The size of the crystals grown was up to 20-30 mm in diameters and 95-135 mm in length. Er:YAG crystal grown under the nitrogen atmosphere was pink and transparent and Er,Cr:YSGG under the 98% {{{{ { N}_{ 2} }}}} and 2% {{{{ { O}_{2 } }}}} was dark green and transparent. Under the polarizing microscopic observations with crossed polar, striations and {211} core facets were detected. Spectroscopic properties for Er,Cr:YSGG laser rods with <111> axis, 80 mm in length and 6.3 mm in diameter for medical laser applications of 2.79 ${\mu}$m wavelength were manufactured and then laser oscillation was achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.735-744
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• 2000

The electrical procerties and stability of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Er$_2$O$_3$ (ZPCCE) based varistors were investigated in the Er$_2$O$_3$content range of 0.0 to 4.0 mol%. ZPCCE ceramics containing 2.0 mol% Er$_2$O$_3$ exhibited the highest density of 5.74 g/㎤ corresponding to 99.3% of theoretical density. The varistors with 0.5 mol% and 2.0 mol% Er$_2$O$_3$exhibited a relatively satisfying nonlinearity, which the nonlinear exponent is 40.50 and 47.15, respectively and the leakage current is 2.66 $mutextrm{A}$, respectively. Under more severe d.c. stress, such as (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$115$^{\circ}C$/12h)+(0.90 V$_{1mA}$12$0^{\circ}C$/12h)+(0.95 V$_{1mA}$1$25^{\circ}C$12h), they showed a very excellent stability, which the variation rate of the variator voltage is -0.89% and -0.15%, the variation rate of the nonlinear coefficient is -4.67% and -3.56%, and the variation rate of leakage current is -6.02% and -19.56%, respectively. It is surely bellived that ZnO-0.5 mol% Pr$_{6}$O$_{11}$-1.0 mol% CoO-0.5 mol% Cr$_2$O$_3$-x mol% Er$_2$O$_3$(x=0.5, 2.0) based varistors will be greatly contributed to develop the advanced Pr$_{6}$O$_{11}$-based ZnO varistors in future.uture. future.uture.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.348-352
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• 2014

In light of the sure protection function, the most important factors of a varistor are the clamping voltage ratio and degradation characteristics. The degradation characteristics of Pr/Co/Cr/Er co-doped zinc oxide varistors were investigated by impulse currents (0.4~2.1 kA) stress for the specified content of $Er_2O_3$ (0.5 and 2.0 mol%). The varistor doped with 2.0 mol% $Er_2O_3$ exhibited the best clamp characteristics, with the clamp voltage ratio (K) in the range of K = 1.63~1.88 at the impulse currents of 5-50 A. However, the varistor doped with 0.5 mol% exhibited excellent electrical stability, with variation rates for the breakdown field, for the nonlinear coefficient, and for the leakage current density of -6.9%, -12.6%, and -14.3%, respectively, after application of an impulse current of 2.1 kA. In contrast, the varistor doped with 2.0 mol% was destroyed after application of an impulse current of 1.2 kA.