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Method for producing transparent alumina sintered body

  • US 10,717,677 B2
  • Filed: 02/23/2018
  • Issued: 07/21/2020
  • Est. Priority Date: 09/30/2015
  • Status: Active Grant
First Claim
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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×

    [x

    T+x

    (100−

    T)+x

    Z]/[y

    T+y

    (100−

    T)+y

    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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