Method for producing transparent alumina sintered body
First Claim
1. A method for producing a transparent alumina sintered body, the method comprising:
- (a) a step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more and a fine alumina powder having an average particle diameter smaller than that of the plate-like alumina powder so that, at a mixing ratio T;
(100−
T) of the plate-like alumina powder to the fine alumina powder in terms of mass ratio, T is 0.001 or more and less than 1, and a mass ratio R1 of F relative to Al in the alumina raw material powder is less than 15 ppm;
(b) a step of forming a raw material for forming containing the alumina raw material powder into a compact; and
(c) a step of sintering the compact so as to obtain a transparent alumina sintered body,where the mass ratio R1 is a value calculated from formula (1) below;
R1=100×
[x1×
T+x2×
(100−
T)+x3×
Z]/[y1×
T+y2×
(100−
T)+y3×
z]
(1)where the unit is mass ppm;
Z is a ratio of an additive externally added to the alumina raw material powder relative to the alumina raw material powder (mass %);
x1 is an F content (mass ppm) in the plate-like alumina powder, x2 is an F content (mass ppm) in the fine alumina powder, and x3 is an F content (mass ppm) in the additive;
the F contents are determined by alkali fusion-ion chromatography;
y1 is an Al content (mass %) in the plate-like alumina powder, and y2 is an Al content (mass %) in the fine alumina powder;
the Al contents are values (mass %) each obtained by determining an alumina purity of each alumina powder as 100−
(sum in terms of mass % of impurity elements other than Al and O), and multiplying the obtained result by 0.529;
the mass % of the impurity elements is determined as follows;
that is, high-frequency heating-infrared absorption spectroscopy is used to determine an S content, an inert gas fusion-thermal conductivity method is used to determine an N content, inert gas fusion-nondispersive infrared absorption spectroscopy is used to determine an H content, alkali fusion-ion chromatography is used to determine an F content, and inductively coupled plasma (ICP) emission spectroscopy is used to determine contents of other elements; and
y3 is an Al content (mass %) in the additive and is determined by inductively coupled plasma (ICP) emission spectrometry.
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Abstract
A method for producing a transparent alumina sintered body according to the present invention includes (a) a step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more and a fine alumina powder having an average particle diameter smaller than that of the plate-like alumina powder so that, when a mixing ratio of the plate-like alumina powder to the fine alumina powder in terms of mass ratio is assumed to be T:(100−T), T is 0.001 or more and less than 1, and so that a mass ratio R1 of F relative to Al in the alumina raw material powder is less than 15 ppm; (b) a step of forming a raw material for forming containing the alumina raw material powder into a compact; and (c) a step of sintering the compact so as to obtain a transparent alumina sintered body.
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Citations
6 Claims
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1. A method for producing a transparent alumina sintered body, the method comprising:
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(a) a step of preparing an alumina raw material powder containing a plate-like alumina powder having an aspect ratio of 3 or more and a fine alumina powder having an average particle diameter smaller than that of the plate-like alumina powder so that, at a mixing ratio T;
(100−
T) of the plate-like alumina powder to the fine alumina powder in terms of mass ratio, T is 0.001 or more and less than 1, and a mass ratio R1 of F relative to Al in the alumina raw material powder is less than 15 ppm;(b) a step of forming a raw material for forming containing the alumina raw material powder into a compact; and (c) a step of sintering the compact so as to obtain a transparent alumina sintered body, where the mass ratio R1 is a value calculated from formula (1) below;
R1=100×
[x1×
T+x2×
(100−
T)+x3×
Z]/[y1×
T+y2×
(100−
T)+y3×
z]
(1)where the unit is mass ppm;
Z is a ratio of an additive externally added to the alumina raw material powder relative to the alumina raw material powder (mass %);
x1 is an F content (mass ppm) in the plate-like alumina powder, x2 is an F content (mass ppm) in the fine alumina powder, and x3 is an F content (mass ppm) in the additive;
the F contents are determined by alkali fusion-ion chromatography;
y1 is an Al content (mass %) in the plate-like alumina powder, and y2 is an Al content (mass %) in the fine alumina powder;
the Al contents are values (mass %) each obtained by determining an alumina purity of each alumina powder as 100−
(sum in terms of mass % of impurity elements other than Al and O), and multiplying the obtained result by 0.529;
the mass % of the impurity elements is determined as follows;
that is, high-frequency heating-infrared absorption spectroscopy is used to determine an S content, an inert gas fusion-thermal conductivity method is used to determine an N content, inert gas fusion-nondispersive infrared absorption spectroscopy is used to determine an H content, alkali fusion-ion chromatography is used to determine an F content, and inductively coupled plasma (ICP) emission spectroscopy is used to determine contents of other elements; and
y3 is an Al content (mass %) in the additive and is determined by inductively coupled plasma (ICP) emission spectrometry. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification