The effects of La3+ substitution for Sr2+-site on the crystal structure and the dielectric properties of (Ba0.7Sr0.3-3x/2Lax) (Ti0.9Zr0.1)O3 (BSLTZ) (0.005 ≤ x ≤ 0.02) ceramics were investigated. The structural characteristics of the BSLTZ ceramics were quantitatively evaluated using the Rietveld refinement method from X-ray diffraction (XRD) data. For the specimens sintered at 1,550 °C for 6 h, a single phase with a perovskite structure and homogeneous microstructure were observed for the entire range of compositions. With increasing La3+ substitution (x), the unit cell volume decreased because the ionic size of La3+ (1.36 Å) ions is smaller than that of Sr2+ (1.44 Å) ions. With increasing La3+ substitution (x), the tetragonal phase fraction increased due to the A-site cation size mismatch effect. Dielectric constant (εr) increased with the La3+ substitution (x) due to the increase in tetragonality (c/a) and the average B-site bond valence of the ABO3 perovskite. The BSLTZ ceramics showed a higher dielectric loss due to the smaller grain size than that of (Ba0.7Sr0.3)(Ti0.9Zr0.1)O3 ceramics. BSLTZ (x = 0.02) ceramics met the X7R specification proposed by the Electronic Industries Association (EIA).

Eu2+ 이온이 도핑된 질화물 형광체 Sr2Si5N8:Eu2+는 탄소열 환원 질화법 (Carbothermal Reduction Nitridation, CRN)을 이용하여 제조된다. X-선 회절분석기를 이용하여 구조를 관찰할 수 있다. 흡수 밴드 피크인 470 nm 는 Photoluminescence Exitation (PLE) 측정을 통해 확인할 수 있다. 이러한 여기 광은 InGaN 기반으로 한 발광다이오 드에 적용시키기에 효과적일 것으로 기대되며, (Sr1-xEux)2Si5N8:Eu2+ 형광체는 Eu2+ 이온 도핑 농도에 따라 628 nm 부터 670 nm 까지의 피크 파장을 얻을 수 있다. Eu2+의 농도가 증가할수록 발광 파장이 길어지는 적색 편이 현상을 관찰할 수 있다. 청색 발광다이오드에 Y3Al5O12:Ce3+ 형광체와 함께 적용하여 우수한 연색성을 갖는 백색광을 얻을 수 있었다.

Eu2+/Dy3+-doped Sr2MgSi2O7 powders were synthesized using a solid-state reaction method with flux (NH4Cl). Thebroad photoluminescence (PL) excitation spectra of Sr2MgSi2O7:Eu2+ were assigned to the 4f7-4f65d transition of the Eu2+ ions,showing strong intensities in the range of 375 to 425nm. A single emission band was observed at 470nm, which was the resultof two overlapping subbands at 468 and 507nm owing to Eu(I) and Eu(II) sites. The strongest emission intensity ofSr2MgSi2O7:Eu2+ was obtained at the Eu concentration of 3mol%. This concentration quenching mechanism was attributableto dipole-dipole interaction. The Ba2+ substitution for Sr2+ caused a blue-shift of the emission band; this behavior was discussedby considering the differences in ionic size and covalence between Ba2+ and Sr2+. The effects of the Eu/Dy ratios on thephosphorescence of Sr2MgSi2O7:Eu2+/Dy3+ were investigated by measuring the decay time; the longest afterglow was obtainedfor 0.01Eu2+/0.03Dy3+.

A study on the electrosorption of Co2+ and Sr2+ ions onto a porous activated carbon fiber (ACF) was performed to treat radioactive liquid wastes resulting from chemical or electrochemical decontamination and to regenerate the spent carbon electrode. The result of batch electrosorption experiments showed that applied negative potential increased adsorption kinetics and capacity in comparison with open-circuit potential (OCP) adsorption for Co2+ and Sr2+ ions. The adsorbed Co2+ and Sr2+ ions are released from the carbon fiber by applying a positive potential on the electrode, showing the reversibility of the sorption process. The possibility of application of the electrosorption technique to the separation of radionuclides was examined. The result of a selective removal experiments of a single component from a mixed solution showed that perfect separation of Co2+ and Sr2+ ions was possible by the electrosorption process.

RF magnetron sputtering 법으로 T a2 O5 세라믹 타겟과 S r2N b2 O7 세라믹 타겟을 동시 sputtering하여 저유전율 S r2(T a1-x , N bx)2 O7(STNO) 박막을 p-type Si (100) 기판 위에 증착하여 NDRO 강유전체 메모리 (Non-destructive read out ferro-electric random access memory)에 사용되는 Pt/STNO/Si (MFS) 구조의 응용 가능성을 확인하였다. Sr2Nb2 O7 (SN O) 타겟과 T a2 O5 타겟의 출력의 비를 100w/100w, 70w/100w, 그리고 50w/100w로 조절하면서 x 값을 달리하여 조성을 변화시켰다. 성장된 박막을 850˚C, 900˚C, 그리고 950˚C에서 1시간 동안 산소 분위기에서 열처리하였다. 조성과 열처리 온도에 따른 구조적 특징을 XRD에 의해 관찰하였으며 표면특성은 FE-SBM에 의해 관찰하였고, C-V 측정과 I-V 측정으로 박막의 전기적 특성을 조사하였다. SNO 타겟과 T a2 O5 타켓의 출력비에 따른 STNO 박막의 성장 결과 70W/170W의 출력비에서 성장된 STNO박막에서 Ta의 양이 상대적 맡은 x=0.4였으며 가장 우수한 C-V 특성 및 누설 전류 특성을 보였다. 이 조성에서 성장된 STNO박막은 3-9V외 인가전압에서 메모리 윈도우 갑이 0.5-8.3V였고 누설전류밀도는 -6V의 인가전압에서 7.9×10-8A /cm2였다.

Bi-계 고온초전도체인 Bi2Sr2Ca2Cu3O10(Bi-2223)단일상을 반응시간을 줄이면서 합성하기 위하여 Bi-Sr-Ca-Cu-O계 내에 존재하는 Bi2Sr2Ca2Cu3O10(Bi-22o1), Bi2Sr2Ca2Cu3O10(Bi-2212), (Ca0.91Sr0.09)-CuO2의 혼합물, 특히 정확한 Bi1.7Pb0.4Sr2Ca2Cu3O10+x의 조성대신 (Ca0.91Sr0.09)CuO2가 많이 첨가된 조성의 혼합물에서 Bi-2223가 가장 쉽게 형성되었다. Bi-2223상은 860˚C와 870˚C에서 60시간 이내에 형성되었다. 소량의 Bi-2212상은 장시간의 반응후에도 여전히 존재하였다. 중간화합물을 이용한 합성방법이 통상의 소결방법에 비해 반응시간내에 소량의 불순물상들을 가진 Bi-2223상을 형성시킬 수 있다.

이온교환 용액내 Na+ 이온의 몰농도 증가에 따른 zeolite A의 Sr2+ 이온교환 특성을 연구하기 위하여, Sr2+ 및 Na+ 이온으로 교환된 4개의 zeolite A 단결정을 혼합 이온교환 용액을 이용하여 회분법으로 준비하였 다. 이들 이온교환용액의 전체 몰농도는 0.05M이며, Sr(NO3)2:NaNO3 몰비는 각각 1:1(crystal 1), 1:100(crystal 2), 1:250(crystal 3), and 1:500(crystal 4) 이다. 이들 단결정은 623 K와 1×10-4 Pa의 진공하에서 2 일간 탈수 시 켰다. 이들의 구조는 단결정 싱크로트론 X-선 회절법으로 입방공간군 Pm3-m을 사용하여 해석하였으며 crystals 1, 2, 3 및 4의 최종 오차 인자를 각각 0.047/0.146, 0.048/0.142, 0.036/0.128, and 0.040/0.156로 정밀화하였다. Crystal 1과 2에서는 6개의 Sr2+ 이온이 결정학적으로 서로 다른 3개의 위치에서 발견되었다. Crystal 3에서는 1 개의 Sr2+ 이온과 10개의 Na+ 이온이 large cavity와 sodalite 내부에서 발견 되었다. Crystal 4 에서는 단지 12 개의 Na+ 이온만이 3개의 서로 다른 결정학적 자리에 점유하고 있었다. Sr2+ 이온의 이온교환율은 초기 Na+ 이온의 농도가 증가하고 Sr2+ 이온의 농도가 감소함에 따라 100에서 16.7 및 0%로 급격하게 감소 하였다. 또한, Sr2+ 이온 교환률이 감소 함에 따라 제올라이트 골격의 단위 격자 상수 값이 갑소 하였다.

Separation of strontium ion from synthetic seawater in the contained liquid membrane permeator with two micro-porous films was performed. The permeator consisted of a liquid membrane and two cells for aqueous solutions. The liquid membrane consisted of D2EHPA(di-2-ethylhexyl-phosphoric acid) and DCH18C6 (dicyclohexano-18-crown-6), diluted to 30 vol % with kerosine and was trapped between two micro-porous hydrophilic films. This liquid membrane separated two aqueous solutions, one of which was synthetic seawater and the other of which was the stripping solutions consisting of 1㏖/L H2SO4 Solution. The effects of various operating parameters on the extraction rate and equilibrium extraction ratio of strontium ion from synthetic seawater were experimentally examined. The addition of DCH18C6 to the D2EHPA solution caused synergy effect on the extraction of strontium ion. The permeator extracted strontium ion from synthetic seawater effectively with high membrane life time.

The three natural zeolites collected in Yungil-gun, Kyungsangbuk-do, Korea, were analyzed by means of chemical wet methods and X-ray diffraction. The results indicated that the primary species of those zeolites were clinoptilolite mixed with heulandite, feldspar, montmorillonite, and quartz. These zeolites were chemically treated with NaOH, Ca(OH)_2, and HCl solution and their differences were also studied with X-ray diffraction method. The capabilities of removing Cs^+ and Sr^2+ ions with chemically untreated zeolites, chemically treated zeolites, and also with synthetic zeolites were compared. The effect of other cations in removing Sr^2+ ions was also studied. The experimental results showed that Cs+ and Sr^2+ ions could be removed up to 98% and 95% respectively out of 5 ppm with chemically untrearted natural zeolites. The treatment of 0.02N-Ca(OH)_2 and that of 2N-NaOH were most effective in removing Cs^+ and Sr^2+ ions, respectively. It was found that the mountaintop of Sangjung 1-dong natural zeolite treated with 2N-NaOH was most efficient in removing Sr^2+ ions mixed with other cations, compared with any other chemically treated and untreated natural zeolites in this work.