• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.488-494
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• 1988

Effects of MnO2 addition on themicrostructure, dielectric and piezoelectric properties of Rhombohedral, Tetragonal and Morphotropic phase boundary(MPB) in Pb(Ni1/3Nb2/3)O3-PbTiO3-PbZrO3 system were investigated and respectively the amount of MnO2 addition was 0, 0.2, 0.5, 1.0, 3.0wt%. In the tetragonal region, compared with the Rhombohedral and Morpotropic phase boundary, Mechanical quality factor(Qm), Curie temperature(Tc) and Dissipation factor were promoted by addition of MnO2. According to the results of the microstructure, dielectric and piezoelectric properties, the solid solution range of MnO2 addition in this system was 0.2-0.5wt%.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.13-16
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• 2003

Mn-doped $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin film phosphors have been grown using a pulsed laser deposition technique under various growth conditions. The structural characterization carr~ed out on a series of $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) films grown on MgO(l00) substrates usmg Zn-rich ceramic targets. Oxygen pressure was varied from 50 to 200 mTorr and Zn/Ga ratio was the function of oxygen pressure. XRD patterns showed that the lattice constants of the $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin film decrease with the substitution of sulfur and selenium for the oxygen in the $ZnGa_2O_4$. Measurements of photoluminescence (PL) properties of $ZnGa_{2}O_{4}$:$Mn^{2+}$ (M=S, Se) thin films have indicated that MgO(100) is one of the most promised substrates for the growth of high quality $ZnGa_2O_{4-x}M_{x}$:$Mn^{2+}$ (M=S, Se) thin films. In particular, the incorporation of Sulfur or Selenium into $ZnGa_2O_4$ lattice could induce a remarkable increase in the intensity of PL. The increasing of green emission intensity was observed with $ZnGa_2O_{3.925}Se_{0.075}:$Mn^{2+}$ and $ZnGa_2O_{3.925}S_{0.05}$:$Mn^{2+}$ films, whose brightness was increased by a factor of 3.1 and 1.4 in comparison with that of $ZnGa_{2}O_{4}$:$Mn^{2+}$ films, respectively. These phosphors may promise for application to the flat panel displays.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.333-340
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• 2006

A (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst were prepared by co-precipitation method and used for low-temperature selective catalytic reduction (SCR) of $NO_x$ with ammonia in the presence of oxygen. The properties of the catalysts were studied by X-ray diffraction (XRD), temperature programmed reduction (TPR) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). The experimental results showed that (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst yielded 81% NO conversion at temperature as low as $150^{\circ}C$ and a space velocity of $2,400\;h^{-1}$. Crystalline phase of $Mn_{2}O_3$ was present at ${\ge}\;15%$ Mn on $V_{2}O_{5}/TiO_{2}$. XRD confirmed the presence of manganese oxide ($Mn_{2}O_{3}$) at $2{\theta}=32.978^{\circ}(222)$. The XRD patterns presented of (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ did not show intense or sharp peaks for manganese oxides and vanadia oxides. The TPR profiles of (5 wt.%)Mn-(1 wt.%)$V_{2}O_{5}/TiO_{2}$ catalyst showed main reduction peat of a maximum at $595^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.2
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• pp.71-76
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• 1992

Piezoceramic filters were fabricated by adding $MnO_2 and FeZ0_3$ to the $0.05Pb(Al_{2/3}W_{1/3})O_3-0.95Pb(Zr_{0.52}Ti0.48)O_3$ system using photolithography method. As the amounts of $MnO_2$ increased, the electro-mechanical coupling factor(Kp) decresed. On the other hand, for $Fe_2O_3$ added samples, Kp was 57%, but mechanical quality factor(Qm) showed relatively low value. The passband widths were 155kHz for 0.3wt % $MnO_2$ addition and 260kHz for 0.1 wt % $Fe_2O_3$ addition, and were inversely propotional to Qm values. Group delay time characteristics showed Gausian for $MnO_2$ additions and Butterworth for$Fe_2O_3$ additions.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.995-1001
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• 1998

As a basic study for cathode materials of {{{{ { {LiMn }_{2 }O }_{4 } }}-based lithium-ion secondary batteries Li({{{{ { { { {Mn }_{1-$\delta$ }Nb }_{$\delta$} )}_{2 }O }_{4 } }} ($\delta$=0.05, 0.1, 0.2) materials which Nb is substituted for Mn were synthesized by the solid state reaction at 80$0^{\circ}C$ and 110$0^{\circ}C$ respectively. The second phase {{{{ { LiNbO}_{3 } }} appeared above $\delta$=0.1 As the result of im-pedance analysis as the amount of substituted Nb increased the resistivity of grain boundary increased greatly. Compared to undoped-{{{{ { {LiMn }_{2 }O }_{4 } }} the electrical conductivity of Li({{{{ { { { {Mn }_{1-$\delta$ }Nb }_{$\delta$} )}_{2 }O }_{4 } }} decreased slightly but is charging capacity and potential plateau increased.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.334-337
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• 2004

Perovskite PMN-PZT-based ceramics were prepared and the$ MnO_2$ doping effects on their piezoelectric properties were investigated. Grain size decreased with increasing the $MnO_2$ content, and the pyrochlore phase was not identified in the sintered PMN-PZT ceramics with 0.01～1.0wt% $MnO_2$. Piezoelectric voltage and charge constants were reduced and mechanical quality factor increased with increasing the $MnO_2$ content. However, electromechanical coupling coefficient slightly decreased with increasing the MnO$_2$ content without regard to the grain size.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.539-545
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• 2016

Alumina added with Mn3O4 up to 7.5 cat% of Mn was prepared by conventional ceramic processing, and the sintering behavior and the optical properties of which were studied as functions of Mn content. Densification and grain growth of alumina were enhanced by Mn addition up to 0.75 cat% but was leveled off at higher concentrations. XRD revealed that $Al_2MnO_4$(galaxite) was formed as a second phase in the specimens with more than 0.75 cat% of Mn. Thus it is believed that either the solid solution effect of Mn or the Zener effect of $Al_2MnO_4$ becomes predominant in the sintering of Mn-added $Al_2O_3$ according to the additive concentration. UV-VIS reflectivity(SCI) spectra of Mn-added $Al_2O_3$ consisted of smooth bottoms in 300~550 nm wavelength range and plateaus at wavelengths longer than 650 nm. The reflectivity spectrum continuously moved downward, and the specimen color became darker and thicker with increasing Mn content. The CIELAB color change with respect to standard white was also dependent on the amount of Mn added: ${\Delta}L^*$(D65) negatively increased and ${\Delta}E_{ab}^*$(D65) positively increased with increasing Mn content, probably due to Mn substitution to Al and/or the mixing effect of black $Al_2MnO_4$ as a second phase.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.687-694
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• 2020

Two oxidizing agents (KMnO4, H2O2), and one neutralizing agent (NaOH) were applied to evaluate Mn removal in mine drainage. A Mn2+ solution and artificial mine drainage were prepared to identify the Fe2+ influence on Mn2+ removal. The initial concentrations of Mn2+ and Fe2+ were 0.1 mM and 1.0 mM, respectively. The injection amount of oxidizing and neutralizing agents were set to ratios of 0.1, 0.67, 1.0, and 2.0 with respect to the Mn2+ mole concentration. KMnO4 exhibited a higher removal efficiency of Mn2+ than did H2O2 and NaOH, where approximately 90% of Mn2+ was removed by KMnO4. A black MnO2 was precipitated that indicated the oxidation of Mn2+ to Mn4+ after an oxidizing agent was added. In addition, MnO2 (pyrolusite) is a stable precipitate under pH-Eh conditions in the solution. However, relatively low removal ratios (6%) of Mn2+ were observed in the artificial mine drainage that included 1.0 mM of Fe2+. The rapid oxidation tendency of Fe2+ as compared to that of Mn2+ was determined to be the main reason for the low removal ratios of Mn2+. The oxidation of Fe2+ showed a decrease of Fe concentration in solution after injection of the oxidizing and neutralizing agents. In addition, Mn7+ of KMnO4 was reduced to Mn2+ by Fe2+ oxidation. Thus, the concentrations of Mn increased in artificial mine drainage. These results revealed that the oxidation method is more effective than the neutralization method for Mn removal in solution. It should also be mentioned that to achieve the Mn removal in mine drainage, Fe2+ removal must be conducted prior to Mn2+ oxidation.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.293-299
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• 1982

The effects of $MnO_2$ and $Cr_2O_3$ on the Piezoelectrictric properties of Pb(Mg1/2W1/2)0.3 Ti0.4 Zr0.3O3 Ceramics. Electromechanical properties in the system in connection with the sintering temperature and the effects of $MnO_2$ and $Cr_2O_3$ addition. The dielectric constant of the ceramics decreased with the additions of $MnO_2$ while the additions of $Cr_2O_3$ increased the value. The Planar coupling factor (Kp) of the ceramics with 0.2wt% $MnO_2$ and with 0.2wt% $Cr_2O_3$ gave the highest value of 0.52 and 0.513 as sintered at 106$0^{\circ}C$, 108$0^{\circ}C$, respectively. The value of mechanical Q-factor were in parallel with the fired density of the ceramics. The optical micrography of the sintered bodies showed that the additions of $MnO_2$ promoted the grain growth, while the additions of $Cr_2O_3$ retarded the grain growth.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.541-546
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• 2006

In this study we have investigated cathodoluminescence (CL) and structural properties of thin film $ZnGa_2O_4:Mn$ oxide phosphor by using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), photoluminescence (PL), and cathodoluminescence. PL emission peaked at 506 nm was observed from the $ZnGa_2O_4:Mn$ phosphor target and it was attributed to the $^4T_1-^6A_1$ transition in $Mn^{2+}$ ion. The color coordinates of the emission were x = 0.09 and y = 0.67. The $ZnGa_2O_4:Mn$ films showed the excitation spectrum peaked at 294 nm by $Mn^{2+}$ ion absorption. It was found that the higher intensity of CL emission at 505 nm appears to result from the denser and closely-packed structure in $ZnGa_2O_4:Mn$ phosphor films deposited at lower pressures. The CL intensity did not show any systematic dependence on film surface roughness.