Multi-composite crystal phase magnetic permeable glass and preparation method thereof

Abstract

The application discloses a kind of multi-composite crystal phase permeable glass and preparation method thereof, including the following mass percentage components: 52-66% SiO2, 10-18% Al2O3, 3-6% B2O3, 2-5% MgO, 2-5% CaO, 1-4% ZnO, 0.5-4% Na2O, 0.5-2% K2O, 0.7-1.2% Ni2O3, 0.5-1.5% CaF2, 0.2-0.4% KCl, 5.5-8% CaCO3, 0.1-0.5% BaCO3, 1-5% BaSO4, 0.1-0.5% Fe2O3, 0.2-0.8% SrO, 0.3-0.6% Nb2O5, 0.5-1.5 CoO, 2-3% carbon powder.The application forms niobium boride crystal phase, ferrite crystal phase and aluminum-nickel-cobalt crystal phase, and prepares multiple-phase composite crystal phase, so that the glass has high permeability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic conducting glass, and particularly relates to a multi-composite crystal phase magnetic conducting glass and a preparation method thereof. BACKGROUND

[0002] Magnetic conducting glass refers to glass in which crystals and crystal phase materials are precipitated during the heating process to form glass with magnetic conducting properties. Chinese patent CN109455927A discloses a magnetic conducting glass formula, which comprises the following components in weight percentage: 60-70% of silicon dioxide, 2-6% of sodium oxide, 4-14% of borax, 2-8% of potassium nitrate, 2-6% of quartz sand, 10-18% of clarifying agent, 6-8% of calcite, and 10-16% of cobalt-manganese-titanium magnetic material. The magnetic conducting glass formula of the patent provides a good platform for the normal use of other elements.

[0003] In recent years, with the rise of the multi-purpose electronic glass industry, the functional requirements for glass substrates have increased, and the expectation of obtaining high-performance magnetic conducting glass through chemical strengthening and other methods has improved. Because glass itself is not a magnetic conducting material, it cannot shield the magnetic field and cannot shield the electromagnetic signal, so by high-temperature electric melting chemical strengthening, the metal ions of various glass raw materials are combined, rearranged and combined into new substances, and the generation of crystal phase inside the glass occurs to improve the special performance of the glass; the addition of other agents can also shorten the melting time of the glass, reduce the melting temperature, and improve the magnetic conductivity of the glass, meeting the needs of privacy communication and electromagnetic interference resistance for windows. Electromagnetic shielding glass mainly solves the anti-electromagnetic interference between computer systems and devices, prevents information leakage, and is suitable for display, plotter, command instrument, shelter communication vehicle, radar display, precision instrument and meter window, and shielding room window. Therefore, it is necessary to develop a new magnetic conducting glass formula and preparation process through chemical strengthening to prepare high-performance magnetic conducting glass. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a multi-composite crystal phase magnetic conducting glass and a preparation method thereof. Through the formula and the stage control of the melting temperature of the magnetic conducting glass, three different crystal phase structures are formed in the glass liquid, i.e. niobium boride crystal phase, ferrite crystal phase and aluminum-nickel-cobalt crystal phase. The three crystal phases melt to form a multi-phase composite crystal phase, which can make the glass have high magnetic conducting performance.

[0005] The technical scheme of the present application is as follows:

[0006] In a first aspect, the present application provides a multi-composite crystal phase permeability glass, comprising the following components in mass percentage: 52-66% SiO2, 10-18% Al2O3, 3-6% B2O3, 2-5% MgO, 2-5% CaO, 1-4% ZnO, 0.5-4% Na2O, 0.5-2% K2O, 0.7-1.2% Ni2O3, 0.5-1.5% CaF2, 0.2-0.4% KCl, 5.5-8% CaCO3, 0.1-0.5% BaCO3, 1-5% BaSO4, 0.1-0.5% Fe2O3, 0.2-0.8% SrO, 0.3-0.6% Nb2O5, 0.5-1.5% CoO, 2-3% carbon powder.

[0007] Preferably, the components include the following mass percentages: 54.5% SiO2, 14% Al2O3, 5% B2O3, 3.5% MgO, 3.5% CaO, 2% ZnO, 2% Na2O, 1% K2O, 0.9% Ni2O3, 0.7% CaF2, 0.3% KCl, 7% CaCO3, 0.2% BaCO3, 2% BaSO4, 0.1% Fe2O3, 0.3% SrO, 0.3% Nb2O5, 0.6% CoO, 2.1% carbon powder.

[0008] The cation coordination number in SiO2 is 4, the cation coordination number in B2O3 is 3, which belongs to a network former, and the single bond strength is greater than 80 kcal / mol, which can independently constitute a glass network; the cation coordination number in Na2O is 8, which belongs to a network outer body, and the single bond strength is less than 60 kcal / mol, which cannot constitute a glass network, but can change the network structure and reduce the glass stability; the cation coordination number in Al2O3 is 6, which belongs to a network intermediate, and the single bond strength is between 60-80 kcal / mol, which can participate in the construction of the glass network under certain conditions.

[0009] B2O3 as a network former, moves in the melt to make various oxides fully mixed in the molten state, increasing the uniformity of the glass solution. B2O3 is a network former and is one of the important components of glass, mainly existing in the form of [BO3] and [BO4] in glass, and existing in the glass network as di-boron, tri-boron, tetra-boron and penta-boron salt groups. Fe2O3 provides iron ions that can promote the conversion of [BO3] to [BO4], and Al 3+ can also be converted to [AlO4], so that the combination of [BO4], [AlO4] and [SiO4] can make the glass network structure more compact, which is helpful for the precipitation of ferrite crystal phase. Therefore, appropriate amount of B2O3 can not only expand the glass forming range and improve the glass forming performance of the system, but also reduce the melting temperature of the glass due to its good fluxing property.

[0010] CaO can effectively melt the glass liquid, can reduce the viscosity in the glass forming, makes the glass easy to melt, plays a good fluxing effect.

[0011] The role of MgO in the glass is similar to CaO, using MgO to replace part of CaO can accelerate the melting and fining of glass, improve the forming properties of glass, destroy the network structure of glass, reduce the viscosity of glass and increase the thermal stability of glass.

[0012] ZnO is a typical intermediate oxide, which can usually be used as a glass former or network modifier, and has different effects on the properties of glass. With the addition of ZnO, the number of non-bridge oxygen bonds in the glass network body increases, resulting in an increase in the voids in the glass network body and a decrease in the density of the glass. On the other hand, the increase in the content of ZnO leads to the conversion of [BO4] groups to [BO3], which enhances the structure of the glass body, reduces the thermal expansion coefficient, and enhances the stability.

[0013] The role of K2O is similar to that of Na2O, which can prolong the glassy nature, enhance the luster and transparency of the glass. When melted into glass, it makes the glass color more transparent and eliminates the blue-green color caused by Fe2O3. K2O in the glass is usually introduced by potassium base (K2CO3) with a specific gravity of 2.29, which often contains trace amounts of Na2CO3, K2SO4, KCl and other impurities, which can be melted.

[0014] Ni2O3 and Fe2O3 can be used together as the network modifier of glass, making the chemical compatibility between the glass body and the ferrite matrix better. Ni2O3 and Fe2O3 can be introduced into the glass as Ni 3+ and Fe 3+ ,which is beneficial to the phase separation of glass, and thus can promote the crystallization of glass during heat treatment. However, the content should not be too high, otherwise the performance of the glass will decrease, such as the increase in the thermal expansion coefficient, the decrease in the elastic modulus, and the decrease in the chemical stability.

[0015] CaF2 acts as a network destroyer in the glass network structure. Since the radius of F- ion is similar to that of O 2- ion, the replacement of bridge oxygen (BO) by F- ion does not affect the arrangement of other ions. However, F - ion is -1 valence, and O 2- ion is -2 valence, so two F- ions are needed to replace one O 2- ion, which is equivalent to replacing two weak silicon-oxygen bonds with one strong silicon-oxygen bond, thereby weakening the network structure of the glass, increasing the mobility and diffusion ability of different ions in the glass, and inducing the crystallization of the glass. At the same time, CaF2 is also a super strong fluxing material of the present application.

[0016] CaCO3 has high thermal stability and chemical stability. CaCO3 can promote the crystallization and crystal growth of glass, thereby enhancing the strength and hardness of glass. In addition, CaCO3 can also reduce the thermal expansion coefficient of glass, improve the high temperature stability and mechanical properties of glass.

[0017] BaCO3 decomposes violently and releases CO2, which makes the glass liquid quickly clear. The quality requirements for barium carbonate are: BaCO3≥98%, and acid insoluble substances <2%.

[0018] BaSO4 can make the magnetic conductive glass have higher hardness, and its decomposition temperature is relatively high (1580°C). Carbon powder should be added to accelerate its decomposition, so the amount should not exceed 5%. The quality requirements for BaSO4 are: BaSO4≥97%, and SiO2<2%.

[0019] Fe2O3 can act as a nucleating agent. After Fe2O3 is added to the glass, there are two valence states of iron ions, Fe 2+ and Fe 3+ . Fe 2+ in FeO plays a role in network destruction in glass, and reacts with Fe 3+ in Fe2O3, i.e. FeO + Fe2O3 = Fe3O4, Fe3O4 plays a role in network formation. The addition of Fe2O3 effectively reduces the crystallization temperature of the glass and facilitates glass phase separation, nucleation and crystal growth.

[0020] Sr belongs to alkaline earth metal elements, its atomic number is relatively large, the ionic radius is also relatively large, and the basicity is relatively strong, only less than barium. Adding SrO into glass can improve the refractive index, dispersion and other optical properties of glass. SrO exists in the form of network outside in glass, fills the glass network gap, and provides free oxygen. Because the electric field strength of Sr 2+ is larger than that of Ba 2+ , the network breaking effect of SrO in glass is not as strong as that of BaO, but the aggregation effect of SrO is stronger than that of BaO, so when a certain amount of SrO is contained, the glass is easy to crystallize.

[0021] After Nb2O5 is doped into the glass system, the number of bridging oxygen connected by [SiO4] increases. A small amount of Nb2O5 is introduced to form [NbO6] niobium oxygen octahedron and [SiO4] silicon oxygen tetrahedron in the form of Si-O-Nb bond into the glass network. The symmetric bridging oxygen Si-O-Si and [BO3] are connected to form B-O-Nb, i.e. B2O3 + Nb2O5 = NbB2. NbB2 will increase the relative content of asymmetric bridging oxygen, and the polymerization degree of glass network connection is higher. The density and molecular molar volume of glass will also gradually increase with the increase of the amount of Nb2O5 doping, which increases the chemical strength of glass.

[0022] The addition of Co in CoO makes the glass have unique magnetic properties besides good mechanical properties. The addition of CoO makes the glass have high magnetic permeability, super-high breaking strength and hardness. Co 2+ than Al 3+ The existence of a large amount of Co 2+ occupies more void positions, making the glass densified. Al 3+ transformation of [AlO4] and [NiO2] and Co 2+ , that is, Al2O3+Ni2O3+2CoO=2AlNiCo+4O2, Co 3+ ions occupy a large number of void positions in the interior of the glass molecules, making the glass produce a strong internal magnetic field effect. Under the joint action of [AlO4] and [NiO2], the t 2g electrons jump to e g state, become high-spin state electrons, making the glass have high magnetism.

[0023] In the second aspect, the application provides a preparation method of the above-mentioned multi-composite crystal phase magnetic conductive glass. The components of the magnetic conductive glass are added to a kiln to start heating and melting. During the heating process, the temperature is raised to 1485±5℃, and the temperature is kept for 10±2s. In the process, niobium boride crystal phase is generated, that is, B2O3+Nb2O5=NbB2. The temperature is continuously raised to 1600±5℃, and the temperature is kept for 15±2s. Then the temperature falls back to 1500±5℃, and the temperature is kept for 30±2s. Then the temperature is raised to 1594±5℃ again, and the temperature is kept for 15±2s. In the process, ferrite crystal phase is generated, that is, FeO+Fe2O3=Fe3O4. The temperature is continuously raised to 1935±5℃, and the temperature is kept for 10±5s. In the process, aluminum-nickel-cobalt crystal phase is generated, that is, Al2O3+Ni2O3+2CoO=2AlNiCo+4O2. The temperature falls back to 1485±5℃, and the temperature is kept for 10±2s. The above process is repeated. The formed niobium boride crystal phase is beneficial to improving the density of the glass, and the ferrite crystal phase and the aluminum-nickel-cobalt crystal phase are beneficial to improving the strength and magnetic conductivity of the glass.

[0024] The formation of the multi-composite crystal phase glass solution of the application: the sodium silicate, calcium silicate and a large amount of silica sand remaining after the reaction generated in the silicate formation stage are dissolved and diffused with each other when the temperature continues to be raised, and the opaque semi-melted sintered material is converted into transparent glass liquid. The niobium boride crystal phase, the ferrite crystal phase and the aluminum-nickel-cobalt crystal phase generated thereafter form a multi-phase composite crystal phase (niobium-aluminum-nickel-cobalt crystal phase) and melt into the glass to form a multi-phase composite crystal phase glass solution. The nanoscale crystal phase is arranged in multiple ways, so that the crystallization performance, the density, the strength and the electrical conductivity of the magnetic conductive glass are improved.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] The present application forms three different crystal phase structures, i.e. niobium boride crystal phase, ferrite crystal phase and aluminum-nickel-cobalt crystal phase, in the glass liquid by the formula of the magnetic conductive glass and the phased control of the melting temperature, and the three crystal phases form a multi-phase composite crystal phase, which can improve the magnetic conductive performance and mechanical performance of the glass. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 SEM image of the niobium boride crystal phase of the multi-composite crystal phase magnetic conductive glass.

[0028] Figure 2 SEM image of the ferrite crystal phase of the multi-composite crystal phase magnetic conductive glass.

[0029] Figure 3 SEM image of the aluminum-nickel-cobalt crystal phase of the multi-composite crystal phase magnetic conductive glass.

[0030] Figure 4 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Example 1 of the present application.

[0031] Figure 5 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Example 2 of the present application.

[0032] Figure 6 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Example 3 of the present application.

[0033] Figure 7 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Example 4 of the present application.

[0034] Figure 8 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Example 5 of the present application.

[0035] Figure 9 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Comparative Example 1 of the present application.

[0036] Figure 10 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Comparative Example 2 of the present application.

[0037] Figure 11 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Comparative Example 3 of the present application.

[0038] Figure 12 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Comparative Example 4 of the present application.

[0039] Figure 13 SEM image of the multi-composite crystal phase magnetic conductive glass prepared in Comparative Example 5 of the present application. DETAILED DESCRIPTION

[0040] In order to make the person skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0041] Examples 1-5 and Comparative Examples 1-5

[0042] The formula of the multi-composite crystalline phase magnetically conductive glass of Examples 1-5 and Comparative Examples 1-5 is shown in Table 1-2:

[0043] Table 1 Formula of the multi-composite crystalline phase magnetically conductive glass of Examples 1-5

[0044]

[0045]

[0046] Table 2 Formula of the multi-composite crystalline phase magnetically conductive glass of Comparative Examples 1-5

[0047]

[0048]

[0049] The preparation method of the multi-composite crystalline phase magnetically conductive glass of Examples 1-5 is that the components of the magnetically conductive glass are added into a kiln to start heating and melting, in the heating process, when the temperature is raised to 1485±5℃, the temperature is kept for 10±2s; when the temperature is continuously raised to 1594±5℃, the temperature is kept for 15±2s; when the temperature is continuously raised to 1935±5℃, the temperature is kept for 10±5s. The process parameters in the preparation process of the multi-composite crystalline phase magnetically conductive glass of Examples 1-5 are shown in Table 3, and the process parameters in the preparation process of the multi-composite crystalline phase magnetically conductive glass of Comparative Examples 1-5 are the same as those of Example 1:

[0050] Table 3 Process parameters in the preparation process of the multi-composite crystalline phase magnetically conductive glass of Examples 1-5

[0051]

[0052]

[0053] Comparative Example 6

[0054] The difference from Example 1 is that the preparation method of the multi-composite crystalline phase magnetically conductive glass is that the components of the magnetically conductive glass are added into a kiln to start heating and melting, in the heating process, when the temperature is raised to 1485℃, the temperature is kept for 10s; when the temperature is continuously raised to 1595℃, the temperature is kept for 10s; when the temperature is continuously raised to 1940℃, the temperature is kept for 10s.

[0055] The method for measuring the density of the multi-composite crystalline phase magnetic glass prepared in Examples 1-5 and Comparative Examples 1-6 is as follows: the density of the glass sample is measured by using the Archimedes principle, the medium liquid is distilled water, and the mass of the sample is measured by using a DE-120 high-density multifunctional electronic densimeter. A small piece of glass sample without defects such as air bubbles and stripes is selected, the sample is cleaned with anhydrous ethanol and dried; first, the mass of the sample in air is measured, enter is clicked, the data is automatically recorded by the instrument and the next step is entered; then, the mass of the sample in distilled water is measured, enter is clicked; the degree displayed by the instrument is the density of the measured sample. The glass density calculation formula is as follows:

[0056] p = p0m2 / (m2-m1)

[0057] In the formula: m1 is the mass of the sample in air, g; m2 is the mass of the sample in distilled water, g; p0 is the density of air.

[0058] The method for measuring the bending strength of the multi-composite crystalline phase magnetic glass prepared in Examples 1-5 and Comparative Examples 1-6 is as follows: the three-point bending method is used to test the bending strength. The glass sample is ground into a strip shape by diamond sand, and is measured by an MTS-800 instrument, the loading speed is 0.5 mm / min, the span is 20 mm, and the detection standard is in accordance with GB6569-86. The bending strength calculation formula is as follows:

[0059]

[0060] In the formula: - the bending strength, MPa; P is the load at the time of fracture, N; L is the span, mm; b is the sample width, mm; h is the sample height, mm.

[0061] The method for measuring the microhardness of the multi-composite crystalline phase magnetic glass prepared in Examples 1-5 and Comparative Examples 1-6 is as follows: the microhardness of the defect-free sample is measured by using an HVS-1000 type microhardness tester, the load is 9.8 N, the loading time is 40 s, four points are taken on each piece of glass, and the average value is taken. The microhardness calculation formula is as follows:

[0062] Hv = P / S = 1.8544P / d 2 ;

[0063] In the formula: Hv is the microhardness of the glass, MPa; P is the load, N; S is the indentation surface area, mm 2 ; d is the average length of the indentation diagonal, mm.

[0064] Saturation magnetization and Curie temperature are intrinsic parameters of materials, which are not sensitive to the change of microstructure of materials. Magnetic materials change with temperature, when the temperature rises to a certain temperature, ferromagnetic or ferrimagnetic materials change from ferromagnetic or ferrimagnetic state to paramagnetic state, and this temperature is called Curie temperature.

[0065] The saturation magnetization of the multi-composite crystalline phase magnetic conductive glass prepared in Examples 1-5 and Comparative Examples 1-6 was tested by using a Nissan 327-25 instrument. The test specification was powder, the inspection standard was HG / T 2347.2-92, and the test condition was room temperature. The saturation magnetization bsx was measured by using a magnetic balance method, which is a method for determining bsx according to the force principle of magnetic substances in a non-uniform magnetic field. The calculation formula is as follows:

[0066]

[0067] In the formula: - the saturation magnetization of the standard sample small nickel ball, e.m.u / g or Am 2 / Kg; m o - the mass of the standard sample small nickel ball, g; ΔW o - the weight difference of the standard sample small nickel ball before and after being subjected to the magnetic field, g; ΔW x - the weight difference of the to-be-tested sample before and after being subjected to the magnetic field, g; m x - the mass of the to-be-tested sample, g.

[0068] The determination method of the resistivity and conductivity of the multi-composite crystalline phase magnetic conductive glass prepared in Examples 1-5 and Comparative Examples 1-6 is as follows: the glass sample is ground into a certain size of quadrilateral by using diamond sand, and a SDY-5-shaped double-electric measuring four-probe tester is used to test the resistivity and conductivity. The calculation formula is as follows:

[0069] P = RS / L;

[0070] σ = 1 / P = L / RS;

[0071] In the formula: P - resistivity, Ω·cm; σ - conductivity, Ω -1 ·cm -1 ; R - resistance of the sample, Ω; S - area of the sample, cm 2 ; L - thickness of the sample, cm.

[0072] The performance test results of the multi-composite crystalline phase magnetic conductive glass prepared in Examples 1-5 and Comparative Examples 1-6 are shown in Tables 4-5.

[0073] Table 4 Performance test results of the multi-composite crystalline phase magnetic conductive glass prepared in Examples 1-5

[0074]

[0075]

[0076] Table 5 shows the performance test results of the multi-composite crystal phase magnetic glass prepared in Comparative Examples 1-6

[0077]

[0078] The SEM images of the niobium boride crystal phase, the ferrite crystal phase and the alnico crystal phase of the multi-composite crystal phase magnetic glass are shown in FIGS. 1-3, respectively. The SEM images of the multi-composite crystal phase magnetic glass of Example 1 and Comparative Examples 1-5 were measured by a JSM-5610V scanning electron microscope, and are shown in FIGS. 4-8, respectively. Figures 1-3 Figures 4-13

[0079] As can be seen from Tables 4-5 and the SEM images, compared with Example 1, the multi-composite crystal phase magnetic glass prepared in Comparative Example 1 does not add Fe2O3, and the ferrite crystal phase is not generated, which leads to a significant decrease in the saturation magnetization, an increase in the resistivity and a decrease in the conductivity.

[0080] Compared with Example 1, the multi-composite crystal phase magnetic glass prepared in Comparative Example 2 does not add Nb2O5, and the niobium boride crystal phase is not generated, which leads to a significant decrease in the microhardness of the glass.

[0081] Compared with Example 1, the multi-composite crystal phase magnetic glass prepared in Comparative Example 3 does not add CoO, which leads to the failure of the generation of the alnico crystal phase, and a decrease in the density and the microhardness of the glass.

[0082] Compared with Example 1, Comparative Example 4 does not add Ni2O3, and Comparative Example 5 does not add SrO, and the performance of the finally prepared glass is decreased. At the same time, it can be seen from Comparative Example 6 that the performance of the prepared glass prepared by using the curve cycle heating method of the present application is better.​​

Claims

1. A multi-composite crystalline phase magnetic glass, characterized in that, It includes the following components by mass percentage: 52-66% SiO2, 10-18% Al2O3, 3-6% B2O3, 2-5% MgO, 2-5% CaO, 1-4% ZnO, 0.5-4% Na2O, 0.5-2% K2O, 0.7-1.2% Ni2O3, 0.5-1.5% CaF2, 0.2-0.4% KCl, 5.5-8% CaCO3, 0.1-0.5% BaCO3, 1-5% BaSO4, 0.1-0.5% Fe2O3, 0.2-0.8% SrO, 0.3-0.6% Nb2O5, 0.5-1.5% CoO, and 2-3% carbon powder; The preparation method of multi-composite crystalline phase magnetic glass involves adding the various components of the magnetic glass into a furnace and heating and melting them. During the heating process, the temperature is raised to 1485±5℃ and held for 10±2s; then raised to 1600±5℃ and held for 15±2s; then the temperature drops to 1500±5℃ and held for 30±2s; then raised to 1595±5℃ and held for 10±2s; then raised to 1935±5℃ and held for 10±5s; then the temperature drops to 1485±5℃ and held for 10±2s, and this cycle is repeated.

2. The multi-composite crystalline phase magnetic glass as described in claim 1, characterized in that, The composition includes the following components by mass percentage: 54.5% SiO2, 14% Al2O3, 5% B2O3, 3.5% MgO, 3.5% CaO, 2% ZnO, 2% Na2O, 1% K2O, 0.9% Ni2O3, 0.7% CaF2, 0.3% KCl, 7% CaCO3, 0.2% BaCO3, 2% BaSO4, 0.1% Fe2O3, 0.3% SrO, 0.3% Nb2O5, 0.6% CoO, and 2.1% carbon powder.

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