PURPOSE: To obtain a composition suitable as an absorber of electromagnetic wave, particularly microwave, and perticularly used for a joint for microwave oven, by dispersing barium titanate having a specific structure and/or composition, into an organic matrix.

CONSTITUTION: The powder of barium titanate smaller than micron is heated in the presence of an additive (lithium fluoride) at a temp. of 1100-1600°C, preferably about 1250°C, thereby the barium titanate powder of more than 1 μ of average diameter, or coagulation body of more than 10 μ, or preferably particles of more than 100 μ, consisting of basic fine crystals of more than 1 μ of average particle size, including more than 50 capacity %, preferably more than 90 capacity % of tetragonal system crystal, of which a mol ratio of Ba/Ti is slightly more than 1, can be obtained. 0.15-0.60, preferably 0.15-0.35 of barium titanate powder is blended to the total capacity of an organic matrix.