MOD 법에 의해 제조된 SBT 강유전 박막의 전기적 특성

천채일 ( Chae Il Cheon ),김정석 ( Jeong Seog Kim ),( D. L. Kwong ) 한국전기전자재료학회 1999 전기전자재료학회논문지 Vol.12 No.2

열처리 분위기가 Eu 이온이 첨가된 Li-Al-O계 형광체 특성에 미치는 영향

김정석,천채일,채기웅,Kim, Jeong Seog,Cheon, Chae Il,Chae, Ki-Woong 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.1

New green phosphor is synthesized by reducing $LiAlO_2:xEu^{3+}$ phosphors in a low pressure $H_2$ atmosphere. The $LiAlO_2:xEu^{3+}$ prepared by a solid state reaction method is reported as red phosphor. The effect of the reduction treatment on the $LiAlO_2:xEu^{3+}$ on the crystalline phase change and photoluminescence (PL) property are characterized. The reduced phosphor had a broad green light spectrum centered at 524 nm. The PL intensity of the reduced phosphor increased to a maximum at the reduction temperature of $1100^{\circ}C$. The PL intensity decreased with a further increase in the reduction temperature. The crystalline phase constituting the reduced phosphor varied with the temperature. A new crystalline phase $Li_2Al_4O_7$ was observed at $1100^{\circ}C$. The origin of the green-light emission is discussed in relation to the crystalline phase change.

Al₂O₃:xCr₂O₃ 고용상의 발광특성과 적색형광체의 연색성 향상을 위한 첨가제로의 응용

채기웅,천채일,김정석,Chae, Ki-Woong,Cheon, Chae-Il,Kim, Jeong-Seog 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.2

In this article photoluminescence of the $Al_2O_3:xCr_2O_3$ solid solutions prepared by solid state reaction method are represented. The effect of $Cr_2O_3$-activator concentration and heat treatment time on the PL characteristics have been discussed in conjunction with microstructure of phosphor samples. The $Al_2O_3:xCr_2O_3$ phosphors show the highest PL intensity at x=0.003 mole when the samples are reacted at $1600^{\circ}C$ for 5 h. The PL emission and absorption spectra show the maximum peaks at 698 nm and at 398 nm respectively. The CIE color coordinate is (x=0.646, y=0.316) at 0.003 mole $Cr_2O_3$, which value is very close to the NTSC coordinate of red color. This characteristic feature of $Al_2O_3:xCr_2O_3$ has been applied for an additive to improve the color characteristic of other red phosphor $LiEuW_2O_8$ which has a relatively poor color purity with an emission peak centered at 615 nm and with a CIE coordinate (x=0.530, y=0.280). The $Al_2O_3:0.003Cr_2O_3$ phosphor has been mixed with the $LiEuW_2O_8$ phosphor powder and the PL characteristics and CIE color coordinates are characterized. The $Al_2O_3:xCr_2O_3$ phosphor was found effective for improving the CRI (color rendering index) of $LiEuW_2O_8$ phosphor.

소결 조건이 스크린 인쇄법으로 제조한 PZT계 후막의 물성에 미치는 영향

이봉연,천채일,김정석,김준철,방규석,이형규,Lee, Bong-Yeon,Cheon, Chae-Il,Kim, Jeong-Seog,Kim, Jon-Chul,Bang, Kyu-Seok,Lee, Hyeung-Gyu 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.10

스크린 인쇄법으로 알루미나 기판 위에 PZT 후막을 제조하였으며, 공기 또는 Pb 분위기의 $750{\sim}1050^{\circ}C$에서 1시간 동안 소결하여 소결 조건이 후막의 물성에 미치는 영향을 조사하였다. 공기 중에서 $950^{\circ}C$ 이상의 온도로 소결한 PZT 후막에는 파이로클로 상이 제 2상으로 존재하고 있었으며, Pb분위기에서 소결한 PZT 후막이 공기 중에서 소결한 후막보다 치밀한 미세구조와 큰 유전상수 그리고 잘 발달된 P-E 이력특성을 보였다. $900^{\circ}C$의 Pb 분위기에서 소결한 PZT 후막은 잘 포화된 전형적인 강유전 P-E 이력곡선 모양을 보였으며, 잔류분극과 항전계가 각각 $29.8{\mu}C/cm^2$, 48.4 kV/cm이었다. PZT thick films were fabricated on alumina substrates by a screen printing method. They were sintered at $750^{\circ}C{\sim}1050^{\circ}C$ for 1 h under air or Pb atmosphere. Pyrochlore was observed as a second phase in PZT thick films sintered in air at temperatures of $950^{\circ}C$ and higher. PZT thick films sintered under Pb atmosphere showed denser microstructure, higher dielectric constant, and better-developed P-E hysteresis curve than the films sintered in air. PZT thick films sintered at $900^{\circ}C$ under Pb atmosphere showed the typical ferroelectric hysteresis with remanent polarization of $29.8{\mu}C/cm^2$ and coercive field of 48.4 kV/cm.

수열 합성 공정 조건이 티탄산 납의 상 형성에 미치는 영향

김경아,김정석,천채일,Kim, Kyoung-A,Kim, Jeong-Seog,Cheon, Chae-Il 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.1

Lead titanate ($PbTiO_3$) powder was prepared from lead nitrate ($Pb(NO_3)_2$) and titania ($TiO_2$) by hydrothermal route. Phase formation process was investigated by observing the phases formed in various experimental conditions like different KOH concentration, reaction temperature and time. $PbTiO_3$ powder was fabricated when the KOH concentration was 0.8M or higher. An intermediate compound, $PbTi_{0.8}O_{2.6}$, was formed at first by a reaction between PbO and $TiO_2$ and changed into $PbTiO_3$ powder with a perovskite crystal structure. A $PbTiO_3$ phase was formed in a shorter time when a KOH concentration was increased from 0.8M to 8M because a driving force for a $PbTiO_3$ formation was increased due to an increase in a degree of supersaturation. And $TiO_2$ (rutile) and $3PbO{\cdot}H_2O$ were observed at room temperature in a 0.8M KOH solution and $TiO_2$(rutile) and PbO (litharge) in a 8M KOH. A $PbTiO_3$phase was also formed in a shorter time at a higher reaction temperature as a reaction temperature influenced the rates for a dissolution and a precipitation.

스크린 인쇄법에 의해 제조한 PMW-PZT 후막의 특성

손진호,김용범,천채일,유광수,김태송,Son, Jin-Ho,Kim, Yong-Bum,Cheon, Chae-Il,Yoo, Kwang-Soo,Kim, Tae-Song 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.1

스크린 인쇄법 및 PZT sol 처리의 복합공정을 적용하여 $30{\mu}m$ 두께의 PMW-PZT 후막을 Pt/$TiO_2$/$SiN_x$Si 기판위에 제작하였다. 그 결과 PZT sol 처리 횟수가 증가함에 따라 후막의 소결 밀도가 증가하고 전기적, 압전 특성의 증진되는 것을 관찰할 수 있었다. $800^{\circ}C$에서 소결한 10회 sol 처리한 PMW-PZT 후막은 745의 유전상수 및 155 pC/N의 $d_33$ 값을 나타내었다. PMW-PZT thick films of about $30{\mu}m$ thickness were fabricated on Pt/$TiO_2$/$SiN_x$Si substrate by the hybrid method of screen printing and PZT sol application. With the increase of the number of the sol application times, the sintered density and electrical properties of PMW-PZT thick films were evidently increased. For the PMW-PZT thick film with PZT sol application of 10-times, the dielectric constant ($\varepsilon_r$) was 745 at the frequency of 100 KHz and thepiezoelectric coefficient ($d_33$) was 155 pC/N at the applied pressure of 1 atm.

공침법에 의한 비스무스 페라이트 나노 분말 제조

김아영(A Young Kim),천채일(Chae Il Cheon) 호서대학교 공업기술연구소 2020 공업기술연구 논문집 Vol.39 No.2

비스무스 페라이트 (BiFeO3)는 강유전성과 강자성을 동시에 나타내는 대표적인 다강체 세라믹스로 고집적 메모리소자, 자기전기 변환소자 등으로의 응용이 기대되는 재료이다. 최근 전자 소재 및 부품의 소형화 및 고성능화가 진행됨에 따라 이러한 요구에 부합할 수 있는 나노 분말의 필요성이 커지고 있다. 본 연구에서는 비스무스 질산염 및 철 질산염을 출발 원료로 선택하고, 침전제로 KOH 용액을 이용하여 공침법으로 BiFeO3 나노 분말을 제조하였으며, BiFeO3 상이 합성되는 수소이온지수 (pH) 조건을 조사하였다. 침전 반응이 일어나는 용액의 pH를 5 ∼ 12 사이로 조절하여 (pH = 5.34, 7.25, 9.63, 11.58) 침전물을 얻은 후 결정화를 위하여 450 ℃∼700 ℃의 온도에서 열처리하였으며, 결정화된 분말을 X-선 회절 분석하여 열처리 온도에 따른 상의 합성과정을 조사하였다. 수소 이온 지수가 9.63에서 침전시킨 후 700 ℃에서 열처리한 경우만 불순물이 없는 순수한 BiFeO3 분말이 합성되었으며, 그 이외의 조건에서는 불순물 상의 다량 포함하고 있었다. Bismuth ferrite (BiFeO3) is a typical multiferroic material which shows ferroelectric and ferromagnetic properties simultaneously and is expected to be applied for high density memories, magnetoelectric coupling devices and so on. Nano-size powder is required to meet a miniaturization and high functionality of the electronic materials and devices. In this work, BiFeO3 nano-sized powder was prepared by co-precipitation method. Bismuth nitrate and iron nitrate were used as raw materials and KOH solution as a precipitant. The pH range for the preparation of a pure BiFeO3 phase is investigated. The pH of the precipitation reaction was controlled in the range of 5 ∼ 12 (pH = 5.34, 7.25, 9.63, 11.58) and the precipitated powder was crystallized at the temperature of 450 ℃∼700 ℃. The pure BiFeO3 nano-powder was prepared only when precipitated at pH of 9.63 and crystallized at 700 ℃.

비스무스 페라이트계 무연 압전 세라믹스

최진홍,김현아,한승호,강형원,이형규,김정석,천채일,Choi, Jin-Hong,Kim, Hyun-Ah,Han, Seung-Ho,Kang, Hyung-Won,Lee, Hyeung-Gyu,Kim, Jeong-Seog,Cheon, Chae-Il 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.9

Recently, many lead-free piezoelectric materials have been investigated for the replacement of existing Pb-based piezoelectric ceramics because of globally increasing environmental interest. There has been remarkable improvement in piezoelectric properties of some lead-free ceramics such as $(Bi,Na)TiO_3-(Bi,K)TiO_3-BaTiO_3$, $(Na,K)NbO_3-LiSbO_3$, and so on. However, no one still has comparable piezoelectric properties to lead-based materials. Therefore, new lead-free piezoelectric ceramics are required. $BiFeO_3$ has a rhombohedrally distorted perovskite structure at room temperature and a very high Curie temperature ($T_C$= 1,100 K). And a very large electric polarization of 50 ~ 60 ${\mu}C/cm^2$ has been reported both in epitaxial thin film and single crystal $BiFeO_3$. Therefore, a high piezoelectric effect is expected also in a $BiFeO_3$ ceramics. The recent research activities on $BiFeO_3$ or $BiFeO_3$-based solid solutions are reviewed in this article.