| 摘要 |
PROBLEM TO BE SOLVED: To obtain a plate heater capable of extremely evenly heating. SOLUTION: In this plate heater, a cover plate 1 and a base plate 2 each having an intergranular component made of AlN sintered material of an yttrium aluminum oxide phase are joined together with a bonding agent layer 4 mainly consisting of AlN and yttrium aluminum oxide, with a heating circuit 3 interposed. A flatness of a heating surface la of the cover plate 1 is set to 20μm or less, and a difference between a maximum value and minimum value of intervals between the heating circuit 3 and the heating surface la is set to 50μm or less.
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