Increasing MnO Content Research Articles

Effect of MnO addition on chemical durability, glass-crystal transition, thermal, structural, optical, EPR, and color properties of Na2O-CaO-P2O5 ternary glass system

This paper investigates the effect of CaO substitution for MnO on the physicochemical properties in 25Na2O-(30-x)CaO-xMnO-45P2O5 (0 ≤ x ≤ 30 mol%) glass system. These materials were elaborated by the conventional melt-quenching technique at 1050 °C. Free-manganese glass is colorless, while the glasses containing manganese are purple. X-ray diffraction (XRD) confirmed the amorphous state of the studied glasses and showed that the annealing of these glasses leads to a mixture of crystalline phases. Replacing Ca-O bonds with more covalent Mn-O ones in the vitreous matrix increased density (ρ) and glass transition temperature (Tg), indicating the strength of the glass network. Infrared and Raman spectroscopies revealed the existence of PO3, PO2 and PO4 units with P-O-P linkages in the glassy network. EPR spectra exhibited absorptions centered at g ≈ 2, characteristic of isolated Mn2+ ions in distorted octahedral coordination and the optical absorption spectra disclosed bands due to Mn2+ and Mn3+ ions. Decreasing the band gap energy values (Eg) with increasing MnO content agrees with strengthening the vitreous network. Chemical durability results showed the existence of ionic exchanges between distilled water and the studied glasses, and good water resistance is detected for glasses with low Mn content (x = 5 and 10 mol%).

Radiation shielding features of Na2O–P2O5 glasses doped with MnO experimentally and using FLUKA and Phy-X

This research focused on examining the radiation shielding performance of (50% - x/2)P2O5-(50%-x/2)Na2O-xMnO (where x = 0, 5, 15, 25, and 33 mol%) glass system. The shielding review covered the radiation of photons, electrons, particles of heavy-charged, and neutrons. Hence, multiple parameters such as coefficient of mass attenuation (μm), transmission and buildup factors (HVL, MFP, EBF, and EABF), effective atomic number for samples (Zeff), and removal cross-section for fast neutron (FNRCS) of the selected samples were investigated. The results are determined experimentally and by employing FLUKA Monte Carlo software and Phy-X (ZeXTRA and PSD) theoretical programs. A relative discrepancy (RD) and a root-mean-square error (RMSE) were applied to verify the deviation between FLUKA and Phy-X values. An excellent agreement is noticed between measured, simulated, and calculated results. The research revealed that increasing MnO content improves the gamma, electron and heavy charged particle shielding efficiency of studied glasses. Although the addition of MnO has an insignificant impact on FNRCS (from 0.086 to 0.092 cm−1), obtained results identified the relationship between the packing density and shield ability against neutrons for ternary phosphate glasses. We found that the HVL values dropped from 13.898 cm to 11.568 cm at 15 MeV. A range of 7–12 for gamma, 8–12 for electron, 10–11 for proton, 10–11 for alpha, and 9–11 for carbon ion was the maximum value of Zeff that could be obtained. These glasses' shielding behaviors were contrasted with those of conventional materials. Accordingly, the sample with the highest mole fraction (x = 33 %) has higher shielding efficiency than ordinary concrete, Pyrex, and RS253-G18. Finally, the studied glass system can be a good compromise between highest effectiveness of shielding, lowest fabrication cost and environment-friendly shield.

Interfacial Behaviour in Ferroalloys: The Influence of FeMn Slag Composition

The present study investigated the interfacial interaction between FeMn alloy and slags of different compositions and basicity from 0.4 to 1.2 in a sessile drop furnace. Interfacial tension between the FeMn alloy and the slags was measured, and the results were analyzed to assess the sensitivity of the applied methodology. The measurement of the interfacial tension was based on combining the results from experiments, multiphase flow simulations in OpenFOAM, equilibrium calculations in FactSage, and calculation of slag density and surface tension based on numerical models. The results demonstrate that the interfacial tension between the FeMn alloy and slag increases with the slag basicity. It was found that the addition of Al_{2}O_{3} to the slag with basicity of 0.8 and 1.2 increases the interfacial tension, while increasing MnO content from 30.0 to 45.0 wt pct does not have any statistically significant influence on the interfacial tension. EPMA analysis of slag and FeMn phases showed that slags at lower basicities and the FeMn alloy form a metal–slag emulsion due to the destabilization of the interface induced by chemical reactions, partial reduction of SiO_{2} in the slag and the mass transfer of Si across the metal–slag interface.

Effects of MnO on the smelting process of vanadium titanomagnetite pre-reduced pellets in an electric furnace

MnO is proven as an effective fluxing additive for high-temperature pyrometallurgy processes. The effects of MnO on the electric furnace smelting of vanadium titanomagnetite pre-reduced pellets were systematically studied in this study. The results indicated that MnO addition could reduce the titanium slag viscosity. The activities of titania and silica in the slag decreased with the increasing MnO content. The external views of slag-iron separation showed that the addition of MnO was beneficial for the separation of iron from the slag. The EPMA results indicated that the reduction degree of vanadium oxides was improved with the MnO additions of 1 wt% and 2 wt%, but mitigated with the further increase of MnO. Moreover, the reduction of titanium oxides was suppressed with the increasing MnO content. Finally, it was concluded that the suitable addition of MnO was 2 wt% under the present smelting conditions.

Clean and efficient extraction of vanadium from vanadium slag: Effect of manganese on the phase composition and vanadium extraction process

Manganese in vanadium slag plays an important role in the clean and efficient extraction of vanadium, attributed to the effect of manganese content on the phase of vanadium slag and the synergistic effects between manganese and roasting additives during the roasting process. In this study, remelting and crystallization method were used to prepare vanadium slag with different MnO mass fractions. The aforementioned effects were examined using XRD, SEM, and roasting-leaching experiments. The results show that manganese in vanadium slag always occupies the lattice of iron and forms (Mn, Fe)(V, Cr)2O4 and (Fe, Mn)2SiO4. With the increasing MnO content, the diffraction peaks of both spinel and olivine shift to a small angle due to the lattice distortion. Moreover, the MnO content has a greater influence on olivine than on spinel. Mn2V2O7 and Ca2V2O7 are the main vanadates of blank roasting and calcification roasting using n(CaO)/n(V2O3) of 2, respectively. During calcification roasting with n(CaO)/n(V2O3) less than 2, calcium vanadate and manganese vanadate coexist in the roasted samples. During leaching, the vanadium leaching rate shows a completely opposite trend after blank roasting and calcification roasting using n(CaO)/n(V2O3) of 2 as the MnO content increases. By reducing the amount of the added calcium salt, the vanadium leaching rate increases slightly compared with that in the case of n(CaO)/n(V2O3) is 2.0, which fluctuates between 83% and 86%. Furthermore, around 30% of manganese in vanadium slag transforms the vanadium-bearing phase and is further transferred to the leaching solution when reducing the amount of calcium salt properly.

Effect of MnO and CaO substitution for BaO on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO-MnO slag

The effect of MnO and CaO substitution for BaO on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO-MnO slag was investigated using the rotating cylinder method and the structure was analyzed by employing FT-IR and XPS. The results showed that the viscosity at various temperatures decreased gradually when MnO content increased from 0wt% to 3wt%, and increased with BaO content rising from 0wt% to 5wt%, which was consistent with the corrected optical basicity (Λcorr). The activation energy for viscous flow (Eη) showed the similar trend. FT-IR and XPS spectra analysis indicated that both [SiO4]-tetrahedral and [AlO4]-tetrahedral were influenced by MnO and BaO content. The [SiO4]-tetrahedral and [AlO4]-tetrahedral network structures were depolymerized due to an increase in the relative fraction of free oxygen (O2−) and decrease of bridging oxygen (O0) with the increasing MnO content. As a larger amount of CaO was substituted by BaO, the trough depth of [SiO4]-tetrahedral and [AlO4]-tetrahedral bands became deeper, indicating the complexity of network structure and polymerization degree of slag increased, which led to an increase in viscosity.

Effect of fluxing treatment on the amorphous forming ability and magnetic properties of FeBP alloy

The effects of the fluxing treatment of B2O3 and MnO on the amorphous forming ability (AFA) and magnetic properties of the Fe85B10P5 alloy prepared with raw materials were investigated. Results indicate that the B2O3-MnO fluxing treatment can significantly improve the AFA of the Fe85B10P5 alloy. The Curie temperatures (Tc) first decrease and then increase with increasing MnO content. The variation of Tc consists well with the change of the position of the diffraction peak corresponding to (200) plane of α-Fe in the annealed ribbons. It has been proved that using MnO instead of CaO during fluxing treatment for the Fe85B10P5 alloy can achieve a better protection for the P element. However, this fluxing agency makes influences on the variation of Fe and Mn elements, which will influence the Bs of Fe-based amorphous alloys.

Biotite geochemistry deciphers magma evolution of Sn-bearing granite, southern Myanmar

Hydrothermal Sn ± W deposits are commonly formed by ore-forming fluids that exsolved from water-saturated granitic magmas. However, the timing of fluid exsolution and its influence on volatiles and ore-forming elements still remain confused. For this purpose, geochemical and OH isotopic compositions of biotite from Late Cretaceous-Eocene granitic intrusions in the Sibumasu terrane (southern Myanmar) are presented. MnO content of biotite is a well negative correlation with the amount of biotite and whole-rock (La/Yb)N ratio, indicating that it could be a good index of granitic magma differentiation. Cl content of biotite from Paleocene granite shows an increased first and subsequently decreased trend with increasing MnO content (0.71–2.36 wt%), suggesting Cl enrichment by magma evolution and depletion by late-stage fluid exsolution. Fluid exsolution is also supported reduced Li contents of biotite and OH isotopic compositions of residual magmatic water equilibrated with high-MnO biotite (δ18O = 7.0 to 8.8‰ and δD = −114 to −93.5‰). All studied biotite grains from Late Cretaceous granite have low Cl contents (0.01–0.11 wt%), decreased Li with increasing MnO contents, and residual magmatic water-like OH isotopic values (δ18O = 6.9‰ and δD = −105‰), indicating that their host granitic melts had undergone fluid exsolution. Importantly, a positive correlation between Sn and MnO contents in biotite suggests that magma differentiation is a dominant process for Sn enrichment. No depletion of Sn by fluid exsolution likely caused by low salinity fluids exsolved from Cl-poor granitic melts, which were estimated by low Cl contents of biotite (<0.2 wt%). The reduced Nb and Ta contents in high-MnO biotite possibly resulted by fractionation of Nb/Ta-bearing minerals during late-stage magma evolution. Moreover, ore-forming fluids equilibrated with hydrothermal muscovite from Sn-bearing quartz veins have consistent OH isotopic compositions (δ18O = 6.8–7.0‰ and δD = −61.9 to −90.2‰) with magmatic water, suggesting that ore-forming fluids probably exsolved from more evolved granitic melts with strong Sn and F enrichment.

Effect of MnO on the microstructure and electrical properties of SnO2–Zn2SnO4 ceramic composites

This work presents the microstructure and electrical properties of MnO-doped SnO2–Zn2SnO4 ceramic composites prepared through conventional ceramic processing. Scanning electron microscopy images reveal that all samples have a compact structure. With increasing MnO content, the grains grow larger and the grain boundaries become unsharp. Energy dispersive spectroscopy results for the sample doped with 0.1 mol% MnO indicate that Mn distributes randomly on the grain surfaces. X-ray diffraction patterns exhibit that all the samples are composed of SnO2 and Zn2SnO4, and the relative intensity of the diffraction peak for Zn2SnO4 increases with increasing MnO content. The relations between the electric field and current density show that all the samples have varistor properties. For the samples doped with 0.2 and 0.3 mol% MnO, the breakdown electric field is so large that it exceeds the measuring range of the instrument, whereas the relative permittivity is as low as about 30 at 100 Hz. In the electric modulus spectra, two sets of relaxation peaks were observed and the corresponding activation energies are enhanced greatly by doping MnO. The effect of MnO on the microstructure and electrical properties indicates that the space charges trapped by oxygen vacancies are the origin of the great permittivity and varistor properties for SnO2–Zn2SnO4 ceramic composites.

Characterization of the Structural Properties of Zinc Phosphate Glass Ceramics Doped with Manganese Ions Following Thermal Treatment

ABSTRACTGlasses of the MnOx · (P2O5)40 · (ZnO)60−x system were prepared by the melt-quenching technique and thermally treated for 2 h at 650°C. To describe the influence of thermal treatment on zinc phosphate glass matrix doped with manganese ions, X-ray diffraction and infrared spectroscopy were used. The X-ray diffraction patterns revealed that the degree of crystallinity gradually decreased with increasing MnO content in the samples up to 5 mol% of MnO2. The manganese ions were also shown to be captured in the vitreous phase. The infrared spectra confirmed that the glass network underwent changes following thermal treatment. The spectra of thermally treated samples contained new peaks and the infrared bands become narrower compared to those of the untreated samples.

Initial Wetting and Spreading Rates Between SiC and CaO-SiO2-MnO Slag

The wetting of CaO-SiO2-MnO slag on silicon carbide was studied with a variety of slag compositions at 1823 K (1550 °C). Wetting experiments were performed by the dispensed drop technique. We observed complete wetting of the slag on SiC (within 1 second) without a bubble reaction regardless of the basicity (=CaO/SiO2 = C/S ratio). However, after 8 seconds, the bubble reaction was observed under conditions of C/S = 0.8 and 1.1, whereas it was not observed at temperatures lower than 1823 K (1550 °C). The contact angle was independent of MnO content, while the spreading rate increased with the increasing MnO content at the early stage of wetting. Inertial force acts on the early stage of spreading, and viscous force acts with lower MnO content due to higher viscosity. The low-viscosity slag did not fit with the nonreactive viscous model. However, the high-viscosity slag fitted the model well.

Effects of MnO on slag viscosity and wetting behaviour between slag and refractory

As more and more Mn bearing iron ores are used to decrease steel cost and deal with the problem of hearth deposition, slag regime change and hearth refractory erosion in blast furnace become more often. To address these problems, it is urgent to clarify the effects of MnO upon the ironmaking production. Herein, the viscosities of slags with different MnO contents were measured for the first time, and the influence mechanism of MnO was analysed by infrared spectrum. The wetting behaviours between slags with different MnO contents and alumina–carbon refractory were investigated. The results showed that meltability temperature and viscosity decrease simultaneously with the increasing MnO content from 0 to 2.0 wt-%. Infrared spectrum analysis also proved that the existence of Mn+, Ca2+ and Mg2+ makes the Si–O bonds peak moving towards high frequency and the asymmetry of Si–O bond increasing, leading to the decrease in viscosity decreasing. In addition, the characteristic temperatures for wetting reaction increased by ∼40°C with the increasing MnO content from 0 to 3 wt-% (basicity = 1.18). The characteristic temperatures decreased by nearly 50°C with the basicity of slag increasing from 1.0 to 1.3 (MnO = 1 wt-%). Therefore, the increasing MnO content in slag accelerates the erosion rate of BF hearth lining and then decreases the campaign life of blast furnace.

Partitioning and structural role of Mn and Fe ions in ionic sulfophosphate glasses.

Ionic sulfophosphate liquids of the type ZnO-Na2O-Na2SO4-P2O5 exhibit surprising glass forming ability, even at slow or moderate cooling rate. As a concept, they also provide high solubility of transition metal ions which could act as cross-linking sites between the sulfate and phosphate entities. It is therefore investigated how the replacement of ZnO by MnO and/or FeO affects the glass structure and the glass properties. Increasing manganese levels are found to result in a monotonic increase of the transition temperature Tg and most of the mechanical properties. This trend is attributed to the change of metal-ion coordination from four-fold around Zn(2+) to six-fold around Mn(2+) ions. The higher coordination facilitates cross-linking of the ionic structural entities and subsequently increases Tg. Raman and infrared spectroscopy show that the structure of these glasses involves only SO4(2-) and PO4 (3-) monomers as well as P2O7(4-) dimers. Replacement of ZnO by MnO is found to favour PO4(3-) over P2O7(4-) species, a trend which is enhanced by co-doping with FeO. Both transition metal ions show, like Zn(2+), a preference to selectively coordinate to phosphate anionic species, as opposed to sodium ions which coordinate mainly to sulfate anions. EPR spectroscopy finally shows that divalent Mn(2+) ions are present primarily in MnO6-clusters, which, in the studied sulfophosphate glasses, convert upon increasing MnO content from corner-sharing to edge-sharing entities.

Structure–property correlations in highly modified Sr, Mn-borate glasses

Highly modified borate glasses with the composition (1−2x)MnO–x(SrO–B2O3) (x=0.46, 0.42, 0.36, 0.25, and 0.20) were prepared and investigated by Raman, infrared (IR), and electron paramagnetic resonance (EPR) spectroscopy. Optical properties were studied in regard to photoluminescence, optical absorption, and refractive index. The Mn2+/Mn3+ equilibrium was shifted towards the divalent manganese ion as a result of the strongly reducing melting conditions employed in this work, which facilitate the preparation of transparent glasses with up to 80mol% total SrO and MnO content. Changes in the optical and physical properties within this glass series were related to structural variations. The structure of glasses with relatively low MnO content was found to involve mainly trigonal [BØ2O]− and tetrahedral [BØ4]− metaborate groups, which are replaced progressively by pyroborate [B2O5]4− and orthoborate [BO3]3− triangular units upon increasing MnO content. At the highest modification level (x=0.20) the structure is built of orthoborate isomeric species in triangular [BO3]3− and tetrahedral [BØ2O2]3− configuration. The latter species form [B3O9]9− rings, which reestablish some degree of network connectivity, as they involve three bridging and six non-bridging oxygen atoms, and this is reflected by the increase of the glass transition temperature for x=0.25 over x=0.20. Micro-Raman measurements showed structural inhomogeneities in these glasses due to chemical isomerization processes involving short- and medium-range order structures. Also, increasing MnO content was shown to cause MnO-clustering in the glasses as revealed by luminescence and EPR measurements.

Competitive Dissolution Mechanism of Sulfur in CaMnSilicate Melts: Structural View

AbstractThe sulfide capacities of the CaOSiO2MnO(Al2O3MgO) slags were measured at 1873 K over a wide composition range using a gas‐slag equilibration method. The effects of MnO content and the MnO ↔ CaO substitution on the sulfide capacity of molten slag were also investigated based on the structural view of silicate melts. In the multicomponent silicate melts containing high MnO (up to about 50 wt%), the sulfide capacity mainly increased with increasing MnO content. Also, the sulfide capacity and the activity of MnO showed a linear relationship with a slope of unity, indicating that MnO is dominant component controlling the sulfur dissolution behavior into CaMnsilicate melts. The sulfide capacity increased as MnO substituted for CaO in the high silica melts (&gt;30 (±5) wt% SiO2), whereas it decreased by increasing the MnO/CaO ratio in the low silica melts (&lt;30(±5) wt% SiO2). This tendency of sulfide capacity resulted in the clock‐wisely rotating iso‐capacity contours from MnO‐free side to MnO‐rich corner in CaMnsilicate melts. The dissolution mechanism of sulfur in CaMnsilicate melts can be explained by the “Competitive dissolution mechanism.”

Influence of valence and coordination of manganese ions on spectral and dielectric features of Na2SO4–B2O3–P2O5 glasses

Sodiumsulpho borophosphate glasses with composition (40−x)Na2SO4–30B2O3–30P2O5: xMnO with x ranging from 0 to 5.0mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 102–105Hz and in the temperature range within 30–250°C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn2+ as well as in Mn3+ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na+ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na+ ions, create bonding defects and free ions viz., [SO4]2−, [POO1/2O2]2−, [POO0/2O3]3–, Na+ and (NaSO4)−. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn2+ ions.

Sulfide Capacity of CaO&amp;ndash;SiO&lt;sub&gt;2&lt;/sub&gt;&amp;ndash;MnO&amp;ndash;Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;&amp;ndash;MgO Slags at 1873 K

The sulfide capacities of the CaO–SiO2–MnO–Al2O3–5 mass% MgO slags were measured at 1873 K over a wide composition range using a gas–slag equilibration method. The effects of basicity and the activity coefficient of sulfide on the sulfide capacity of molten slag were also investigated based on the structural view of silicate melts. In the multicomponent silicate melts containing high MnO (up to about 50 mass%), the sulfide capacity mainly increased with increasing MnO content. The capacity and modified Vee ratio, i.e. (CaO+MnO+MgO)/ (SiO2+Al2O3), showed a good linear relationship. Assuming that the basicity and the stability of sulfide ions in the slag are proportional to the activity of basic oxides and the activity coefficient of sulfides, the composition dependency of the sulfide capacity is well described by changes in the aMO to γMS (M=Ca, Mn) ratio. The substitution of silica by alumina did not affect the sulfide capacity of the slags not only because of an increase in the activity of basic oxides but also because of a decrease in the stability of sulfides as Al2O3/SiO2 ratio increased. In the high silica melts of which silica content greater than about 30 mass%, the sulfide capacity increased with increasing MnO/CaO ratio, whereas it decreased by increasing the MnO/CaO ratio in the low silica melts (< about 30 mass%). This tendency of sulfide capacity resulted in the clock-wisely rotating iso-capacity contours in the CaO–SiO2–MnO–Al2O3–MgO system at 1873 K. The dissolution mechanism of sulfur in the MnO–containing calcium silicate melts can be explained not only by the difference in the structural role of Ca2+ and Mn2+ ions but also by the changes in the content of O2– ions according to the silica content.

Density Measurements of CaO^|^ndash;MnO^|^ndash;SiO2 Slags

Density measurements of CaO–MnO–SiO2 slags were carried out using the Archimedean method. The density decreased with increasing temperature, and the negative temperature coefficient (–dρ/dT) was in the range of 1.46–3.10 × 10–1 kg/m3 K. At a fixed CaO content (25 wt%) and at a fixed SiO2 content (30 wt%), the density of CaO–MnO–SiO2 slag increased with increasing MnO content. The molar volumes of CaO, MnO and SiO2 at 1773 K were estimated 21.0, 17.2, and 28.0 × 10–6 m3/mol, respectively. The molar excess volume was expressed by VEx = ΩXSiO2 (1–XSiO2), where Ω = –8.97 × 10–6 m3/mol at 1773 K. The thermal expansion coefficient decreased with increasing XSiO2 because of the enhanced silicate network structure.

Intense red photoluminescence from Mn^2+-doped (Na^+; Zn^2+) sulfophosphate glasses and glass ceramics as LED converters

We report on intense red fluorescence from Mn(2+)-doped sulfophosphate glasses and glass ceramics of the type ZnO-Na(2)O-SO(3)-P(2)O(5). As a hypothesis, controlled internal crystallization of as-melted glasses is achieved on the basis of thermally-induced bimodal separation of an SO(3)-rich phase. Crystal formation is then confined to the relict structure of phase separation. The whole synthesis procedure is performed in air at <or= 800 degrees C. Electron spin resonance and Raman spectroscopy indicate that Mn(2+) species are incorporated on Zn(2+) sites with increasingly ionic character for increasing concentration. Correspondingly, in the glasses, increasing MnO content results in decreasing network polymerization. Stable glasses and continuously increasing emission intensity are observed for relatively high dopant concentration of up to 3 mol.%. Recrystallization of the glass results in strongly increasing emission intensity. Dynamic emission spectroscopy reveals only on type of emission centers in the glassy material, whereas three different centers are observed in the glass ceramic. These are attributed to octahedrally coordinated Mn(2+) in the residual glass phase and in crystalline phosphate and sulfate lattices, respectively. Relatively low crystal field strength results in almost ideal red emission, peaking around 625 nm. Excitation bands lie in the blue-to-green spectral range and exhibit strong overlap. The optimum excitation range matches the emission properties of GaN- and InGaN-based light emitting devices.

Effect of MnO addition on structure and electrical properties of (Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 ceramics prepared by citrate method

(Na 0.5Bi 0.5) 0.94Ba 0.06TiO 3 ceramics added with 0–0.8 wt.% MnO were prepared by a citrate method, and the influence of the MnO addition on the structure and electrical properties was investigated. The results indicate that the addition of small amounts of MnO did not cause a remarkable change in crystal structure, but resulted in an evident evolution in microstructure. The dielectric constant ( ɛ r) and piezoelectric constant ( d 33) significantly decrease with increasing MnO content, while the electromechanical coupling factor ( k p) presents a slight variation in the range of 0.25–0.28. The dissipation factor (tan δ) and mechanical quality factor ( Q m) attain a minimum value of 1.5% and a maximum value of 304 when adding 0.4 and 0.5 wt.% MnO, respectively. This research demonstrates that doping effect and microstructural evolution contribute cooperatively to the electrical properties of the ceramics.