MAGNESIA, METHOD FOR MANUFACTURING SAME, HIGHLY THERMALLY CONDUCTIVE MAGNESIA COMPOSITION, AND MAGNESIA CERAMIC USING SAME

Abstract

The present invention discloses magnesia and a method for manufacturing same, wherein the magnesia can be produced into granules of various shapes and sizes and can be improved in moisture resistance with the formation of a moisture resistant surface oxide layer by donor addition and then thermal treatment. The magnesia according to the present invention comprises a MgO granule; and a surface oxide layer formed on a surface of the MgO granule and a composition of the surface oxide layer is different from a composition of an inside of the MgO granule.

Claims

1.-7. (canceled)

8. Magnesia (MgO), comprising: a MgO granule; and a surface oxide layer formed on a surface of the MgO granule, wherein a composition of the surface oxide layer is different from a composition of an inside of the MgO granule.

9. The magnesia (MgO) of claim 8, wherein a donor at an inside of the surface oxide layer comprises at least one of TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, B.sub.2O.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, or Al.sub.2O.sub.3.

10. (canceled)

11. The magnesia (MgO) of claim 8, wherein the magnesia comprises TiO.sub.2 and Nb.sub.2O.sub.5 and satisfies the following Equation (6):
MgO+x wt. % of TiO.sub.2+y wt. % of Nb.sub.2O.sub.5≤100 wt. %   Equation (6) (In Equation (6), x and y are 0<x,y≤2.0 and the remainder is MgO.

12. A magnesia (MgO) comprising: a MgO granule: and a surface oxide layer formed on a surface of the MgO granule. wherein density of the surface oxide layer is higher than density of an inside of the MgO granule.

13. The magnesia (MgO) of claim 17, wherein a donor at an inside of the surface oxide layer comprises at least one of TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, B.sub.2O.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Al.sub.2O.sub.3.

14. Magnesia (MgO), comprising: wherein a MgO granule; and a surface oxide layer formed on a surface of the MgO granule. an inside of the surface oxide layer is higher than a content of a donor at an inside of the granule.

15. (canceled)

16. The magnesia (MgO) of claim 1, wherein the donor at the inside of the surface oxide layer comprises at least one of TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, B.sub.2O.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Al.sub.2O.sub.3.

Description

DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a conceptual diagram showing formation of a dense surface oxide layer by thermal treatment, and a picture of microstructures of a surface oxide layer and an inside of a sintered body during production of the MgO granule of the present disclosure.

[0027] FIG. 2 is a microstructure picture showing shapes and sizes of MgO granules produced according to a producing method of the present disclosure and a microstructure picture of a surface thereof before and after thermal treatment (at 1400° C. for 2 h).

[0028] FIG. 3 is a picture showing a difference between water resistance of a MgO raw material powder and water resistance of a MgO granule thermally treated (at 1400° C. for 2 h) after adding a donor to a MgO powder.

[0029] FIG. 4 is a microstructure picture of fracture surfaces of a sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+0.2 wt. % of SiO.sub.2 (at a left side) and a sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5 (at a right side), which are thermally treated at 1400° C. for 2 h, to identify thicknesses of surface oxide layers thereof.

[0030] FIG. 5 shows an energy dispersive X-ray spectroscopy (EDS) analysis results and microstructure pictures used to identify formation of a surface oxide layer including a MgO-donor in a sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+0.2 wt. % of SiO.sub.2 which is thermally treated at 1400° C. for 2 h.

[0031] FIG. 6 is a graph showing changes in thermal diffusivity of a sample sintered after adding a TiO.sub.2 composition to magnesia (MgO).

[0032] FIG. 7 is a graph showing a change in thermal diffusivity of a sample sintered after adding an Nb.sub.2O.sub.5 composition to magnesia (MgO).

[0033] FIG. 8 is a graph showing a change in thermal diffusivity and a change in density of a sample sintered after adding a trace amount of TiO.sub.2 (or Nb.sub.2O.sub.5) composition to magnesia (MgO).

[0034] FIG. 9 is a graph showing changes in thermal diffusivity and density of a sample sintered after adding 0.3 wt. % of TiO.sub.2+a trace amount of Nb.sub.2O.sub.5 composition to magnesia (MgO).

[0035] FIG. 10 is a graph showing changes in thermal diffusivity of a sample sintered after adding a ZrO.sub.2 composition to magnesia (MgO).

[0036] FIG. 11 is a graph showing changes in thermal diffusivity of samples sintered after adding 0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+a ZrO.sub.2 composition to magnesia (MgO).

[0037] FIG. 12 is a graph showing a change in thermal diffusivity of a sample sintered after adding an Al.sub.2O.sub.3 composition to magnesia (MgO).

[0038] FIG. 13 is a graph showing changes in thermal diffusivity and density of samples sintered after adding 0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+a trace amount of Al.sub.2O.sub.3 composition to magnesia (MgO).

[0039] FIG. 14 is a picture of microstructures of fracture surfaces of a sample in which a 2.0 wt% of TiO.sub.2 composition is added to magnesia (MgO) and a sample in which 2.0 wt% of ZrO.sub.2 composition is added to magnesia (MgO), which are electron-microscopically observed after sintering at 1400° C. for 2 hours, respectively.

BEST MODE

[0040] The above-mentioned objects, features, and advantages of the present disclosure are described in detail with reference to accompanying drawings. Therefore, a person having ordinary knowledge in the art to which the present disclosure pertains may easily implement the technical idea of the present disclosure. In the description of the present disclosure, a detailed description of a well-known technology relating to the present disclosure may be omitted if it unnecessarily obscures the gist of the present disclosure. Preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings. In the drawings, same reference numerals are used to refer to same or similar components.

[0041] Hereinafter, magnesia, a method for producing the magnesia, a highly thermally conductive magnesia composition, and magnesia ceramics using the same according to some embodiments of the present disclosure are described.

[0042] According to the present disclosure, the method for producing the magnesia includes adding a donor and an organic solvent to a MgO powder to prepare a mixture, drying the mixture, forming a donor-added MgO granule from the mixture, and thermally treating the donor-added MgO granule.

[0043] In addition, a surface oxide layer is formed on the surface of the MgO granule by thermally treating the donor-added MgO granule and has a different composition from that of an inside of the MgO granule.

[0044] In the present disclosure, the donor refers to a metal oxide having a higher metal valence than that of MgO and an oxide having a trivalent valence or higher.

[0045] Meanwhile, in the method for producing the magnesia of the present disclosure, Mg(OH).sub.2 may be used instead of the MgO powder. When the Mg(OH).sub.2 is used, linear shrinkage of a sintered body and the granule after the thermal treatment is 20 to 40%, which is significantly different from 10 to 30% of linear shrinkage in the case of using the MgO.

[0046] When producing the magnesia using a Mg(OH).sub.2 powder as a starting material instead of the MgO powder, it is preferable to add distilled water instead of an organic solvent. Magnesia may be produced under the same conditions as the conditions of a method for producing magnesia using the MgO powder described below, except that the starting material Mg(OH).sub.2 and the distilled water are used.

[0047] The following producing method is described as a method for producing magnesia using the MgO powder.

[0048] In the step of adding a donor and an organic solvent to the MgO powder to prepare a mixture, the MgO powder is mixed in a solution prepared by dissolving and dispersing the donor in the organic solvent to prepare a mixture.

[0049] A small amount of 0.01 to 10.0 wt. % of a donor including at least one of TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, B.sub.2O.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Al.sub.2O.sub.3 is added relative to a total of .sub.100 wt. % of the MgO powder and the donor.

[0050] When the amount of the donor added is outside of the above range, the magnesia may be difficult to have moisture resistance and thermal conductivity as a ceramic filler for thermal interface material.

[0051] After the donor and the organic solvent are added to the MgO powder, a mixture is formed by mixing and pulverizing them by ball milling.

[0052] In the step of forming the mixture, the pulverization may be performed for 0.5 to 72 hours.

[0053] If the pulverizing time period is less than 0.5 hours, that is, is too short, the mixing and pulverizing effects of the MgO and donor additives may be insufficient. If the pulverizing time period exceeds 72 hours, the pulverizing time period may be too long, thereby making an inefficient process.

[0054] 2-propanol, anhydrous alcohol, and the like may be used as the organic solvent, and the distilled water may also be used. When the distilled water is used, Mg(OH).sub.2 is formed. In this case, the sintered body and the granule have linear shrinkage of 20 to 40%, which is significantly different from linear shrinkage of 10 to 30% of the sintered body and the granule after the thermal treatment when 2-propanol or the anhydrous alcohol is used.

[0055] Drying the mixture is performed to remove the organic solvent. The organic solvent may be removed by natural drying at 25±5° C. or drying at 25° C. or higher.

[0056] In the step of forming the donor-added MgO granules from the mixture, the MgO granule may be formed from the MgO powder using various methods.

[0057] For example, MgO granules of various sizes may be formed from the MgO powder and a donor-added MgO granule may be formed by rotating at a rotation speed of 10 to 500 rpm using a cylindrical container. In this case, based on comparison between the powder and the granule, a particle size of the granule is larger than that of the powder.

[0058] The donor-added MgO granule may also be produced in the same manner as the method for forming the MgO granule and may be produced by dispersing the donor on the surface of the MgO granule.

[0059] The thermal treatment of the donor-added MgO granule may be performed at 800 to 1800° C.

[0060] During the thermal treatment, a portion of the donor is moved to the surface of the granule to form a surface oxide layer including MgO and the donor. Accordingly, the surface oxide layer including the MgO-donor is formed on the surface of the MgO granule during the thermal treatment.

[0061] The thermal treatment is preferably performed in a temperature range from 800 to 1800° C., and if the thermal treatment temperature is outside of the above range, an oxide layer may not be properly formed on the surface of the MgO granule as a surface protective layer.

[0062] Similar to the above-described producing method, producing magnesia using the Mg(OH).sub.2 powder as the starting material may include adding a donor and distilled water to the Mg(OH).sub.2 powder to form a mixture, drying the mixture, forming a donor-added Mg(OH).sub.2 granule from the mixture, and thermally treating the donor-added Mg(OH).sub.2 powder. Matters of the donor and the thermal treatment are as described above.

[0063] FIG. 1 is a conceptual diagram showing formation of a dense surface oxide layer by thermal treatment, and a picture of a microstructure of a surface oxide layer and an inside of a sintered body during production of the MgO granule of the present disclosure.

[0064] As shown in FIG. 1, some donors move along a grain boundary and are collected on a surface of the granule in the thermal treatment process. Accordingly, a surface oxide layer having a dense microstructure that is different from that of an inside of the MgO granule is formed and a surface oxide layer having a composition that is different from that of an inside of the MgO granule is formed on the surface of the granule.

[0065] In the present disclosure, low moisture resistance of the MgO may be improved by forming the surface oxide layer.

[0066] As described above, in the present disclosure, a surface oxide layer including the MgO and the donor are formed as a protective layer on the surface of the MgO granule using a method for producing magnesia by forming a donor-added MgO granule or a donor-added Mg(OH).sub.2 granule using a MgO powder raw material or Mg(OH).sub.2 powder raw material and then thermally treating, thereby obtaining moisture resistance and excellent thermal properties.

[0067] For example, the surface oxide layer including metal oxides such as Mg.sub.2TiO.sub.4 and Zr.sub.0.904Mg.sub.0.096O.sub.1.904 including Mg and at least one of metal elements other than the Mg is free from the moisture absoption problem, thereby improving the moisture resistance of MgO.

[0068] Magnesia prepared from the MgO powder raw material or the Mg(OH).sub.2 powder raw material of the present disclosure includes a MgO granule and a surface oxide layer formed on the surface of the MgO granule. In this case, for the magnesia, the surface oxide layer has a different composition from that of the inside of the MgO granule and includes MgO and the donor.

[0069] The surface oxide layer has a dense microstructure compared to the microstructure of the inside of the MgO granule.

[0070] The donor is a metal oxide having a higher metal valence than that of the MgO and includes at least one of TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, B.sub.2o.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Al.sub.2O.sub.3.

[0071] The donor (the metal oxide) material may be included in an amount of 0.01 to 10.0 wt. %, preferably 0.01 to 2.0 wt. %, relative to a total of 100 wt. % of the magnesia.

[0072] Specifically, the magnesia (MgO) includes TiO.sub.2 and Nb.sub.2O.sub.5 and satisfies the following Equation (6).

MgO+x wt. % of TiO.sub.2+y wt. % of Nb.sub.2O.sub.5≤100 wt. %   Equation (6)

[0073] In Equation (6), x and y are 0<x,y≤2.0 and the remainder is MgO.

[0074] FIG. 2 is a microstructure picture showing shapes and sizes of MgO granules produced according to a producing method of the present disclosure, and a microstructure picture of surfaces thereof before and after thermal treatment (at 1400° C. for 2 h).

[0075] Referring to FIG. 2, MgO granules having various sizes and shapes may be produced under producing conditions (rpm). Compared to the MgO granule before the thermal treatment, a surface oxide layer formed on the surface of the MgO granule after the thermal treatment shows a dense microstructure.

[0076] The surface oxide layer has a dense microstructure compared to the microstructure of the inside of the MgO granule.

[0077] FIG. 3 is a picture showing a difference between water resistance to a MgO raw material powder and water resistance to a MgO granule formed by adding a donor to a MgO powder and thermally treating (at 1400° C. for 2h).

[0078] The MgO raw material powder is a powder to which a donor is not added, and Mg(OH).sub.2 was observed on a surface of the powder when the MgO raw material powder is maintained for 72 hours in an environment at a temperature of 85° C. and humidity of 85%.

[0079] In contrast, when the granule is prepared from the donor-added MgO powder according to the producing method of the present disclosure and by thermally treating at 1400° C. and is maintained for 72 hours in an environment of a temperature of 85° C. and humidity of 85%, Me(OH).sub.2 was not observed on a surface of the granule.

[0080] According to the present disclosure, these results show that the MgO granule formed by adding the donor to the MgO powder raw material and that is subjected to thermal treatment did not react with water, thereby improving moisture resistance.

[0081] FIG. 4 is a picture of a microstructure of fracture surfaces of a sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+0.2 wt. % of SiO.sub.2 (at a left side) and a sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5 (at a right side), which are thermally treated at 1400° C. for 2h, to identify thicknesses of surface oxide layers thereof.

[0082] A surface oxide layer is formed by thermally treating the donor-added MgO and is different from an inside of a sample (a granule). It may be seen that a surface oxide layer including MgO-donor and having a thickness of 0.1 to 3 μm was formed in the sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+0.2 wt. % of SiO.sub.2. A surface oxide layer thinner than 0.1 μm was also observed in a TEM image of the sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5.

[0083] FIG. 5 is an energy dispersive X-ray spectroscopy (EDS) analysis results and a microstructure picture used to identify formation of a surface oxide layer including a MgO-donor in a sample of MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+0.2 wt. % of SiO.sub.2 thermally treated at 1400° C. for 2h.

[0084] A surface oxide layer having a different phase from that of an inside thereof was formed by thermally treating the donor-added MgO.

[0085] It was found that a MgO content at an inside of the sample was higher than a MgO content on a surface of the sintered sample, which simplifies that a surface oxide layer including an MgO-donor is formed on the surface of the sintered body.

[0086] In addition, the content of the donor inside the surface oxide layer was higher than the content of the donor inside the MgO granule, which simplifies that the donor was added in an amount of 2.0 wt. % or less relative to 100 wt. % of magnesia, and a concentration of the donor in the surface oxide layer was higher than an average concentration of the donor of a whole (the granule and the surface oxide) and the content of the donor in the surface oxide layer is higher than that of the donor in the granule. The content of the donor in the surface oxide layer was measured at a concentration of at least twice or more, preferably three times or more, more preferably 10 times or more than the content of the donor at the inside of the granule.

[0087] According to the present disclosure, the highly thermally conductive magnesia (MgO) composition includes TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, or Al.sub.2O.sub.3 in a MgO matrix and satisfies the following Equation (1), Equation (2), Equation (3), or Equation (4).

MgO+x wt. % of TiO.sub.2≤100 wt. %   Equation (1)

MgO+y wt. % of Nb.sub.2O.sub.5≤100 wt. %   (2)

MgO+z wt. % of ZrO.sub.2≤100 wt. %   (3)

MgO+w wt. % of Al.sub.2O.sub.3≤100 wt. %   Equation (4)

[0088] In Equations (1) to (4), x, y, z, and w are 0<x, y, z, w<10.0 and the remainder is MgO.

[0089] Preferably, x may satisfy a range of 0<x<10.0 in Equation (1), y may satisfy a range of 0<y<5.0 in Equation (2), z may satisfy a range of 0<z<4.0 in Equation (3), and w may satisfy a range of 0<w<0.8 in Equation (4). More preferably, y may satisfy a range of 0<y<1.0 in Equation (2).

[0090] Referring to FIG. 6 and Table 1, it may be seen that, when titanium dioxide (TiO.sub.2) is added to the magnesia (MgO) as a donor in an amount of exceeding 0 wt. % and equal to or less than 10.0 wt. %, thermal diffusivity of magnesia (MgO) ceramics according to the present disclosure is increased.

[0091] In particular, referring to FIGS. 6, 8 and Table 1, it may be seen that, when the titanium dioxide (TiO.sub.2) is added to the magnesia (MgO) as the donor in an amount of exceeding 0 wt. % and equal to or less than 2.0 wt. % and the magnesia (MgO) ceramics are sintered at 1400° C., thermal diffusivity thereof is similar or superior to that of magnesia (MgO) ceramics sintered at 1700° C.

[0092] In addition, referring to FIGS. 6, 8, and Table 1, it may be seen that, when the titanium dioxide (TiO.sub.2) is added to the magnesia (MgO) as a donor in an amount of exceeding 0 wt. % and equal to or less than 10.0 wt. % and is sintered at 1300° C. to 1400° C., the TiO.sub.2 donor-added magnesia (MgO) has a high relative density of 96% or more in all compositions, which is significantly improved over a relative density of 80 to 90% of the magnesia (MgO) ceramics sintered at a same sintering temperature.

[0093] In addition, it may be seen that thermal diffusivity of the composition sintered at a low temperature of 1300 to 1400° C. after adding titanium dioxide (TiO.sub.2) in an amount of exceeding 0 wt. % and equal to or less than 10.0 wt. % to the magnesia (MgO) is higher than that of the magnesia (MgO) sintered at a same sintering temperature.

[0094] Referring to FIGS. 7 and 8, when niobium pentoxide (Nb.sub.2O.sub.5) is added to magnesia (MgO) as a donor in an amount of exceeding 0 wt. % and equal to or less than 5.0 wt. %, magnesia (MgO) ceramics according to the present disclosure sintered at 1300 to 1400° C. has thermal diffusivity that is similar or superior to that of magnesia (MgO) ceramics sintered at 1700° C.

[0095] In particular, referring to FIGS. 7 and 8, it may be seen that, when 1.0 wt. % or less of niobium pentoxide (Nb.sub.2O.sub.5) is added to the magnesia (MgO) as a donor, the sample sintered at 1400° C. has superior thermal diffusivity than that of the magnesia (MgO) ceramics sintered at 1700° C.

[0096] In FIG. 9, it may be seen that, when 0.3 wt. % of TiO.sub.2 is fixed and Nb.sub.2O.sub.5 is further added in an amount of 1.0 wt. % or less, an improvement in thermal conductivity of magnesia (MgO) ceramics is observed.

[0097] Referring to FIG. 10, it may be seen that, when zirconium oxide (ZrO.sub.2) is added to the magnesia (MgO) as a donor in an amount of exceeding 0 wt. % and equal to or less than 4.0 wt. %, the magnesia (MgO) ceramics according to the present disclosure sintered at 1400° C. has similar thermal diffusivity to that of magnesia (MgO) ceramics sintered at 1700° C.

[0098] Referring to FIG. 11, it may be seen that, even when titanium dioxide (TiO.sub.2), the niobium pentoxide (Nb.sub.2O.sub.5), and the zirconium oxide (ZrO.sub.2) are added together to the magnesia (MgO) as donors, thermal diffusivity of a sample sintered at 1300 to 1400° C. is similar or superior to thermal diffusivity of magnesia (MgO) ceramics sintered at 1700° C.

[0099] In particular, referring to FIG. 11, 0.3 wt. % of titanium dioxide (TiO.sub.2), 0.3 wt. % of niobium pentoxide (Nb.sub.2O.sub.5), and the zirconium oxide (ZrO.sub.2) in an amount of exceeding 0 wt. % and equal to or less than 0.05 wt. % are added to the magnesia (MgO) as donors, it may be seen that thermal diffusivity of magnesia (MgO) ceramics according to the present disclosure is significantly higher than that of the magnesia (MgO) ceramics sintered at 1700° C.

[0100] Referring to FIG. 12, it may be seen that thermal diffusivity of magnesia (MgO) ceramics according to the present disclosure is increased when alumina (Al.sub.2O.sub.3) is added to the magnesia (MgO) as a donor in an amount of exceeding 0 wt. % and equal to or less than 0.8 wt. %.

[0101] In FIG. 13, when 0.3 wt. % of TiO.sub.2 and 0.3 wt. % of Nb.sub.2O.sub.5 were fixed and Al.sub.2O.sub.3 was further added, the thermal conductivity property thereof was not significantly deteriorated and a similar thermal conductivity tendency was observed.

[0102] The highly thermally conductive magnesia (MgO) composition according to the present disclosure includes TiO.sub.2, Nb.sub.2O.sub.5, and ZrO.sub.2 in the MgO matrix and satisfies the following Equation (5).

MgO+0.3 wt. % of TiO.sub.2+0.3 wt. % of Nb.sub.2O.sub.5+z wt. % ZrO.sub.2≤100 wt. %

[0103] In Equation (5), z is 0<z≤0.05 and the remainder is MgO.

[0104] As described above, referring to FIGS. 6 to 13 and Table 1, the sample in which a small amount of at least one metal oxide composition of trivalent or higher valent TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, B.sub.2O.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.5, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Al.sub.2O.sub.3, which may act as donors, was added to MgO had an improved thermal property over a sample in which a donor was not added to the MgO.

[0105] According to the present disclosure, the method for producing magnesia ceramics includes adding a donor to magnesia (MgO) and mixing the donor and the magnesia (MgO), producing at least one of highly thermally conductive magnesia (MgO) composition, drying the composition, and sintering the composition. The sintering may be performed at 1200 to 1500° C.

[0106] Sinterability thereof may be improved by adding at least one material that may act as a donor, thereby achieving low-temperature sintering of the magnesia (MgO).

[0107] The donor includes at least one of TiO.sub.2, Nb.sub.2O.sub.5, ZrO.sub.2, Ga.sub.2O.sub.3, Mn.sub.2O.sub.3, Fe.sub.2O.sub.3, SnO.sub.2, MnO.sub.2, SiO.sub.2, V.sub.2O.sub.5, Ta.sub.2O.sub.4, Sb.sub.2O.sub.5, Y.sub.2O.sub.3, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Al.sub.2O.sub.3.

[0108] Magnesia (MgO) ceramics of the present disclosure is formed by adding an appropriate amount of titanium dioxide (TiO.sub.2), niobium pentoxide (Nb.sub.2O.sub.5), zirconium oxide (ZrO.sub.2) and/or alumina (Al.sub.2O.sub.3) to magnesia (MgO) as donors and mixing them in 2-propanol as a solvent in a ball mill, and subsequently pulverizing and drying them. The mixed powder is molded at a pressure of 100 MPa in a circular metal mold having a diameter of 15 mm and is sintered for two hours at a temperature of 1200° C. to 1500° C. using an electric furnace or a gas furnace to prepare magnesia ceramics.

[0109] Highly thermally conductive magnesia (MgO) ceramics produced by the producing method of the present disclosure may have a relative density value of 93% to 100% compared to theoretical density (3.58 g/cm.sup.3) of magnesia (MgO). Alternatively, when a donor element heavier than Mg is added, highly thermally conductive magnesia (MgO) ceramics may have a density higher than 3.58 g/cm.sup.3. The highly thermally conductive magnesia (MgO) ceramics may have a thermal diffusivity value of 10.4 mm.sup.2/s to 21.9 mm.sup.2/s.

[0110] FIG. 14 is a picture of microstructures of fracture surfaces electron-microscopically observed after sintering a sample in which a 2.0 wt. % of TiO.sub.2 composition is added to magnesia (MgO) and a sample in which 2.0 wt. % of ZrO.sub.2 composition is added to magnesia (MgO) at 1400° C. for 2 h.

[0111] Referring to FIG. 14, when the samples were sintered at 1400° C., the samples have a dense microstructure.

[0112] As described above, specific embodiments of magnesia, a producing method thereof, a highly thermally conductive magnesia composition, and magnesia ceramics using the same are as follows.

[0113] 1. Density

[0114] Density was measured by Archimedes method using xylene.

[0115] 2. Thermal Diffusivity

[0116] Thermal diffusivity was measured using a laser flash method. (LFA 457, MicroFlash, Netzsch Instruments Inc., Germany)

[0117] [Table 1] shows density and thermal diffusivity properties of samples produced by sintering magnesia (MgO) compositions in a temperature range provided by the present disclosure.

TABLE-US-00001 TABLE 1 Sintering Thermal Addition Amount (wt. %) Temper- Diffu- Additive ature Density sivity Classification TiO.sub.2 Nb.sub.2O.sub.2 ZrO.sub.2 Al.sub.2O.sub.3 V.sub.2O.sub.5 B.sub.2O.sub.3 Y.sub.2O.sub.3 SiO.sub.2 Eu.sub.2O.sub.3 Er.sub.2O.sub.3 Fe.sub.2O.sub.3 (° C.) (g/cm.sup.3) (mm.sup.2/s) Embodiment 1 0.5 1300 3.48 16.4 Embodiment 2 0.5 1300 3.52 16.6 Embodiment 3 10.0 1300 3.53 10.4 Embodiment 4 0.5 1300 3.02 12.6 Embodiment 5 4.0 1300 3.11 12.6 Embodiment 6 1.0 1300 3.37 15.5 Embodiment 7 3.0 1300 3.42 15.5 Embodiment 8 0.3 0.3 1300 3.44 16.9 Embodiment 9 0.3 0.3 0.05 1300 3.54 20.5 Embodiment 10 0.3 0.3 1300 3.51 17.4 Embodiment 11 0.3 0.3 0.2 1300 3.54 18.0 Embodiment 12 0.3 0.3 0.2 1300 3.38 15.6 Embodiment 13 0.3 0.3 0.2 1300 3.50 18.1 Embodiment 14 0.3 0.3 0.1 1350 3.55 18.4 Embodiment 15 0.3 0.3 0.1 1350 3.54 18.2 Embodiment 16 0.5 1400 3.56 19.3 Embodiment 17 1.5 1400 3.57 18.6 Embodiment 18 10.0 1400 3.59 12.9 Embodiment 19 2.0 1400 3.51 18.9 Embodiment 20 3.0 1400 3.52 17.0 Embodiment 21 1.0 1400 3.55 18.8 Embodiment 22 2.0 1400 3.57 15.3 Embodiment 23 0.8 1400 3.44 14.2 Embodiment 24 0.3 0.3 1400 3.58 21.0 Embodiment 25 0.3 0.3 0.05 1400 3.59 21.9 Embodiment 26 0.3 0.3 0.2 1400 3.51 16.3 Embodiment 27 0.3 0.3 0.2 1400 3.58 16.3 Embodiment 28 0.3 0.3 0.2 1400 3.53 18.9 Embodiment 29 0.3 0.3 0.2 1400 3.56 21.1 Embodiment 30 0.3 0.3 0.1 1400 3.56 19.5 Embodiment 31 0.3 0.3 0.1 1400 3.57 18.6 Embodiment 32 0.1 0.2 0.6 0.03 0.1 0.01 1400 3.56 17.5 Comparative 1300 2.85 10.1 Example 1 Comparative 1400 3.23 13.1 Example 2 Comparative 1700 3.53 17.0 Example 3

[0118] Embodiment 1: 0.5 wt. % of titanium dioxide (TiO.sub.2) was added to magnesia (MgO) as a donor, was mixed with magnesia (MgO) in 2-propanol as a solvent in a ball mill, and then they were pulverized and dried.

[0119] After molding the dried mixed powder at a pressure of 100 MPa in a circular metal mold having a diameter of 15 mm, the mixed powder was sintered for 2 hours at a temperature of 1300° C. using an electric furnace.

[0120] Embodiments 2 to 32: Highly thermally conductive magnesia ceramics were prepared in the same manner as in Embodiment 1, except that titanium dioxide (TiO.sub.2), niobium pentoxide (Nb.sub.2O.sub.5), zirconium oxide (ZrO.sub.2), alumina (Al.sub.2O.sub.3), V.sub.2O.sub.5, B.sub.2O.sub.3, Y.sub.2O.sub.3, SiO.sub.2, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, and Fe.sub.2O.sub.3 were added to the magnesia (MgO) of Embodiment 1 as donors, in addition amounts shown in Table 1 and they were sintered at a temperature of 1300° C. or 1400° C.

[0121] Comparative Example 1: Magnesia ceramics were produced in the same manner as in Embodiment 1, except that a donor was not added to the magnesia (MgO) of Embodiment 1.

[0122] Comparative Example 2: Magnesia ceramics were produced in the same manner as in Embodiment 1, except that a donor was not added to the magnesia (MgO) of Embodiment 1 and the magnesia (MgO) was sintered at a temperature of 1400° C.

[0123] Comparative Example 3: Magnesia ceramics were produced in the same manner as in Embodiment 1, except that a donor was not added to the magnesia (MgO) of Embodiment 1 and the magnesia (MgO) was sintered at a temperature of 1700° C.

[0124] Referring to Table 1, it may be seen that the sintering of the magnesia (MgO) composition is sufficiently performed in the temperature range of 1300° C. to 1400° C. and the density and the thermal diffusivity of the magnesia (MgO) ceramics change according to the composition ratio of the donor.

[0125] Specifically, referring to Embodiments 1 to 32, when at least one of titanium dioxide (TiO.sub.2), niobium pentoxide (Nb.sub.2O.sub.5), zirconium oxide (ZrO.sub.2) alumina (Al.sub.2O.sub.3), V.sub.2O.sub.5, B.sub.2O.sub.3, Y.sub.2O).sub.3, SiO.sub.2, Eu.sub.2O.sub.3, Er.sub.2O.sub.3, or Fe.sub.2O.sub.3 was added to magnesia (MgO) in a sintering temperature range from 1300° C. to 1400° C., it may be seen that the magnesia (MgO) ceramics according to the present disclosure has an excellent sintering density value of 3.02 g/cm.sup.3 to 3.59 g/cm.sup.3 and an excellent thermal diffusivity value of 10.4 mm.sup.2/s to 21.9 mm.sup.2/s.

[0126] As described above, it may be seen that the highly thermally conductive magnesia (MgO) ceramics produced by the producing method according to the present disclosure has a higher sintering density value than that of the magnesia (MgO) ceramics in the related art. In this case, the highly thermally conductive magnesia (MgO) ceramics produced using the producing method according to the present disclosure has a higher thermal diffusivity value that that of the magnesia (MgO) ceramics in the related art and may be applied to a heat dissipating ceramic material.

[0127] The present disclosure has been described as described above with reference to exemplary drawings; however, the present disclosure is not limited to the embodiments and the drawings disclosed herein, and various modifications can be made by those skilled in the art within the scope of the technical idea of the present disclosure. Further, even if working effects obtained based on configurations of the present disclosure are not explicitly described in the description of embodiments of the present disclosure, effects predictable based on the corresponding configuration have to be recognized.