• Title/Summary/Keyword: Bi$^{3+}$ doping

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Effects of Mn Doping on Structural and Magnetic Properties of Multiferroic BiFeO3 Nanograins Made by Sol-gel Method

  • Raghavender, A.T.;Hong, Nguyen Hoa
    • Journal of Magnetics
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    • v.16 no.1
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    • pp.19-22
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    • 2011
  • [ $BiFeO_3$ ]is a multiferroic material that attracts attentions of many research groups due to its potential as being ferroelectric and ferromagnetic above room temperature. We have prepared both undoped- and Mn-doped $BiFeO_3$ by sol-gel auto-ignition method. Doping of Mn has resulted in decreasing grain size from 60 to 32 nm. X-ray diffraction data show that the samples are pure and single-phase. Infrared measurements on $BiFeO_3$ and Mn-doped $BiFeO_3$ revealed intrinsic stretching vibrations of tetrahedral sites of $Fe^{3+}$-O and of octahedral $Bi^{3+}$-O as well. On the other hand, as the Mn concentration increases, the magnetic moment of $BiFeO_3$ increases. It gives some suggestions in manipulating structural and magnetic properties of $BiFeO_3$ by doping Mn.

The Electrical Properties of Mo-doped BiNbO4 Ceramic Thick Film Monopole Antenna (Mo을 치환한 BiNbO4 세라믹 후막 모노폴 안테나의 전기적 특성)

  • 서원경;허대영;최문석;안성훈;정천석;이재신
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.11
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    • pp.987-993
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    • 2003
  • We fabricated thick film monopole antennas using Mo-doped BiNbO$_4$ ceramics and investigated their electrical properties as a function of the Mo-doping concentration. Compared with undoped BiNbO$_4$ ceramics, 10 at.% Mo-doping improved microwave dielectric properties of ceramics by increased sintered density as well as decreased space charge density. Further increase in the Mo-doping concentration caused formation of Bi$_2$MoO$_{6}$ phases, resulting in deterioration of the microwave characteristics. The gain and bandwidth of the ceramic monopole antenna were also greatly affected by the Mo-doping concentration. When Mo-doping concentration was 10 at.%, highest gain of -0.7dBi with lowest bandwidth of 30% at 2.3GHz was obtained.

Thermoelectric Properties in the Cu Doping Effects of the n-type Bi-Te Powders (Bi-Te계 n형 열전분말의 열전특성에 미치는 Cu 도핑의 영향)

  • Park, Min Soo;Koo, Hye Young;Ha, Gook Hyun;Park, Yong Ho
    • Journal of Powder Materials
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    • v.22 no.4
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    • pp.254-259
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    • 2015
  • $Bi_2Te_3$ related compounds show the best thermoelectric properties at room temperature. However, n-type $Bi_2Te_{2.7}Se_{0.3}$ showed no improvement on ZT values. To improve the thermolectric propterties of n-type $Bi_2Te_{2.7}Se_{0.3}$, this research has Cu-doped n-type powder. This study focused on effects of Cu-doping method on the thermoelectric properties of n-type materials, and evaluated the comparison between the Cu chemical and mechanical doping. The synthesized powder was manufactured by the spark plasma sintering(SPS). The thermoelectric properties of the sintered body were evaluated by measuring their Seebeck coefficient, electrical resistivity, thermal conductivity, and hall coefficient. An introduction of a small amount of Cu reduced the thermal conductivity and improved the electrical properties with Seebeck coefficient. The authors provided the optimal concentration of $Cu_{0.1}Bi_{1.99}Se_{0.3}Te_{2.7}$. A figure of merit (ZT) value of 1.22 was obtained for $Cu_{0.1}Bi_{1.9}Se_{0.3}Te_{2.7}$ at 373K by Cu chemical doping, which was obviously higher than those of $Cu_{0.1}Bi_{1.9}Se_{0.3}Te_{2.7}$ at 373K by Cu mechanical doping (ZT=0.56) and Cu-free $Bi_2Se_{0.3}Te_{2.7}$ (ZT=0.51).

The effects of Mo doping on Electrical Properties of $BiNbO_{4}$ Ceramic Thick Film Monopole Antenna (Mo 치환한 $BiNbO_{4}$ 세라믹 후막 모노폴 안테나의 전기적 특성)

  • Seo, Won-Kyung;Ahn, Sung-Hun;Jung, Chun-Suk;Lee, Jae-Shin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.11a
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    • pp.300-304
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    • 2002
  • We fabricated thick film monopole antennas using Mo-doped $BiNbO_{4}$ ceramics and investigated their electrical properties as a function of the Mo-doping concentration. Compared with undoped $BiNbO_{4}$ ceramics, 10 at.% Mo-doping improved microwave dielectric properties of ceramics by increased sintered density as well as decreased space charge density. Further increase in the Mo-doping concentration caused formation of $Bi_{2}MoO_{6}$ phases, resulting in deterioration of the microwave characteristics. The gain and bandwidth of the ceramic monopole antenna were also greatly affected by the Mo-doping concentration. When Mo-doping concentration was 10 at%, highest gain of ~0.7dBi with lowest bandwidth of 30% at 2.3GHz was obtained.

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Ionic Doping Effect in Bi-layered Perovskite SrBi2Nb2O9 Ferroelectrics (비스무스 층구조형 페로브스카이트 SrBi2Nb2O9 강유전체의 이온 치환 효과)

  • Park, S.E.;Cho, J.A.;Song, T.K.;Kim, M.H.;Kim, S.S.;Lee, H.S.
    • Korean Journal of Materials Research
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    • v.13 no.12
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    • pp.846-849
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    • 2003
  • Doping effect of various ions in Bi-layered ferroelectric $SrBi_2$$Nb_2$$O_{9}$ (SBN) ceramics was studied. Undoped SBN ceramic and SBN ceramics doped with $Ba^{2+}$, $Pb^{2+}$,$ Ca^{2+}$ , $Bi^{3+}$ , $La^{3+}$ , $Ti^{4+}$ , $Mo^{6+}$ , and $W^{6+}$ ions were made by a solid state reaction. Dielectric constants were measured with temperature. Ferroelectric transition temperature decreased with $Pb^{2+}$ , $Ba^{2+}$ , $La^{3+}$ doping, but the transition temperature increased with $Ca^{2+}$ , $Bi^{3+}$ , $Ti^{4+}$, $Mo^{6+}$ , or$ W^{6+}$ ionic doping. These results show that the ion size plays an important role in the ferroelectricity of SBN ceramic.

Phase Evolution Behavior of (Bi,Nd)(Fe,Ti)O3 Ceramics and Thin Films ((Bi,Nd)(Fe,Ti)O3 세라믹스와 박막의 상형성 거동)

  • Kim, Kyung-Man;Lee, Hee-Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.12
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    • pp.949-955
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    • 2010
  • Nd and Ti co-doped bismuth ferrite $(Bi_{1-x}Nd_x)(Fe_{1-y}Ti_y)O_3$ (x, y = 0, 0.05, 0.1, 0.2) ceramics and thin films were synthesized through the conventional mixed-oxide process and pulsed laser deposition (PLD), respectively. Nd and Ti co-doping effect was examined with emphasis on how these impurities affect phase formation behavior as there could be the improvement in leakage current problems often associated with multiferroic $BiFeO_3$ (BFO) thin films. The lattice constants of BFO ceramics decreased with Nd doping concentration up to 10mol%, while they further decreased with Nd and Ti co-doping to about 20%. BFO thin films obtained by the PLD process revealed random polycrystalline structure. Similar to bulk BFO ceramic, Nd and Ti co-doping effectively suppressed the formation of unwanted secondary phase and thus stabilized the perovskite phase in BFO thin films.

Crystal Structure and Microstructure Variation of Nonstoichiometric Bi1±xFeO3±δ and Ti-doped BiFeO3 Ceramics under Various Sintering Conditions (비화학양론적 Bi1±xFeO3±δ와 Ti가 첨가된 BiFeO3의 소결조건에 따른 결정구조와 미세구조 변화)

  • Bae, Jihee;Kim, Jun Chan;Kim, Myong-Ho;Lee, Soonil
    • Korean Journal of Materials Research
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    • v.30 no.2
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    • pp.61-67
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    • 2020
  • BiFeO3 with perovskite structure is a well-known material that has both ferroelectric and antiferromagnetic properties called multiferroics. However, leaky electrical properties and difficulty of controlling stoichiometry due to Bi volatility and difficulty of obtaining high relative density due to high dependency on the ceramic process are issues for BiFeO3 applications. In this work we investigated the sintering behavior of samples with different stoichiometries and sintering conditions. To understand the optimum sintering conditions, nonstoichiometric Bi1±xFeO3±δ ceramics and Ti-doped Bi1.03Fe1-4x/3TixO3 ceramics were synthesized by a conventional solid-state route. Dense single phase BiFeO3 ceramics were successfully fabricated using a two-step sintering and quenching process. The effects of Bi volatility on microstructure were determined by Bi-excess and Ti doping. Bi-excess increased grain size, and Ti doping increased sintering temperature and decreased grain size. It should be noted that Ti-doping suppressed Bi volatility and stabilized the BiFeO3 phase.

Study on Thermoelectric Properties of Cu Doping of Pulse-Electrodeposited n-type Bi2(Te-Se)3 Thin Films (펄스 전기도금법에 의해 제조된 n형 Bi2(Te-Se)3 박막의 Cu 도핑에 따른 열전특성에 관한 연구)

  • Heo, Na-Ri;Kim, Kwang-Ho;Lim, Jae-Hong
    • Journal of the Korean institute of surface engineering
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    • v.49 no.1
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    • pp.40-45
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    • 2016
  • Recently, $Bi_2Te_3$-based alloys are the best thermoelectric materials near to room temperature, so it has been researched to achieve increased figure of merit(ZT). Ternary compounds such as Bi-Te-Se and Bi-Sb-Te have higher thermoelectric property than binary compound Bi-Te and Sb-Te, respectively. Compared to DC plating method, pulsed electrodeposition is able to control parameters including average current density, and on/off pulse time etc. Thereby the morphology and properties of the films can be improved. In this study, we electrodeposited n-type ternary Cu-doped $Bi_2(Te-Se)_3$ thin film by modified pulse technique at room temperature. To further enhance thermoelectric properties of $Bi_2(Te-Se)_3$ thin film, we optimized Cu doping concentration in $Bi_2(Te-Se)_3$ thin film and correlated it to electrical and thermoelectric properties. Thus, the crystal, electrical, and thermoelectric properties of electrodeposited $Bi_2(Te-Se)_3$ thin film were characterized the XRD, SEM, EDS, Seebeck measurement, and Hall effect measurement, respectively. As a result, the thermoelectric properties of Cu-doped $Bi_2(Te-Se)_3$ thin films were observed that the Seebeck coefficient is $-101.2{\mu}V/K$ and the power factor is $1412.6{\mu}W/mK^2$ at 10 mg of Cu weight. The power factor of Cu-doped $Bi_2(Te-Se)_3$ thin film is 1.4 times higher than undoped $Bi_2(Te-Se)_3$ thin film.

Modulation of Microstructure and Energy Storage Performance in (K,Na)NbO3-Bi(Ni,Ta)O3 Ceramics through Zn Doping (Zn 도핑을 통한 (K,Na)NbO3-Bi(Ni,Ta)O3 세라믹의 미세구조 및 에너지 저장 물성 제어)

  • Jueun Kim;Seonhwa Park;Yuho Min
    • Journal of Powder Materials
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    • v.30 no.6
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    • pp.509-515
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    • 2023
  • Lead-free perovskite ceramics, which have excellent energy storage capabilities, are attracting attention owing to their high power density and rapid charge-discharge speed. Given that the energy-storage properties of perovskite ceramic capacitors are significantly improved by doping with various elements, modifying their chemical compositions is a fundamental strategy. This study investigated the effect of Zn doping on the microstructure and energy storage performance of potassium sodium niobate (KNN)-based ceramics. Two types of powders and their corresponding ceramics with compositions of (1-x)(K,Na)NbO3-xBi(Ni2/3Ta1/3)O3 (KNN-BNT) and (1-x)(K,Na)NbO3-xBi(Ni1/3Zn1/3Ta1/3)O3 (KNN-BNZT) were prepared via solid-state reactions. The results indicate that Zn doping retards grain growth, resulting in smaller grain sizes in Zn-doped KNN-BNZT than in KNN-BNT ceramics. Moreover, the Zn-doped KNN-BNZT ceramics exhibited superior energy storage density and efficiency across all x values. Notably, 0.9KNN-0.1BNZT ceramics demonstrate an energy storage density and efficiency of 0.24 J/cm3 and 96%, respectively. These ceramics also exhibited excellent temperature and frequency stability. This study provides valuable insights into the design of KNN-based ceramic capacitors with enhanced energy storage capabilities through doping strategies.

Photocatalytic study of Zinc Oxide with bismuth doping prepared by spray pyrolysis

  • Lin, Tzu-Yang;Hsu, Yu-Ting;Lan, Wen-How;Huang, Chien-Jung;Chen, Lung-Chien;Huang, Yu-Hsuan;Lin, Jia-Ching;Chang, Kuo-Jen;Lin, Wen-Jen;Huang, Kai-Feng
    • Advances in nano research
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    • v.3 no.3
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    • pp.123-131
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    • 2015
  • The unintentionally doped and bismuth (Bi) doped zinc oxide (ZnO) films were prepared by spray pyrolysis at $450^{\circ}C$ with zinc acetate and bismuth nitrate precursor. The n-type conduction with concentration $6.13{\times}10^{16}cm^{-3}$ can be observed for the unintentionally doped ZnO. With the increasing of bismuth nitrate concentration in precursor, the p-type conduction can be observed. The p-type concentration $4.44{\times}10^{17}cm^{-3}$ can be achieved for the film with the Bi/Zn atomic ratio 5% in the precursor. The photoluminescence spectroscopy with HeCd laser light source was studied for films with different Bi doping. The photocatalytic activity for the unintentionally doped and Bi-doped ZnO films was studied through the photodegradation of Congo red under UV light illumination. The effects of different Bi contents on photocatalytic activity are studied and discussed. Results show that appropriate Bi doping in ZnO can increase photocatalytic activity.