Abstract: A vapor chamber includes a first cover, a second cover, a sealing ring and a sealing plug. The first cover has a thermal contact surface. The second cover is coupled with the first cover so as to form an interior space together, and the second cover has a vent hole. The sealing ring has a channel and at least one opening. The opening is in fluid communication with the channel, the sealing ring is clamped between the first cover and the second cover, and the vent hole is in fluid communication with the interior space via the channel and the opening. The vent hole and the channel are plugged with the sealing plug so as to seal the interior space.

Abstract: An alkaline earth metal aluminosilicate sintered body is obtained by molding a starting mixture of a zeolite having an alkaline earth metal form and an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio not higher than 3.0 and a boron compound such as boron oxide, and firing the molded body at a temperature lower than 1,000.degree. C. An amorphous calcination product formed by calcining the zeolite may also be used in the starting mixture with the boron compound. This process allows the range of firing temperatures suitable for formation of a sintered body to be varied over a range of from about 50.degree. to 150.degree. C. or more while also allowing lower firing temperatures than in the absence of the boron compound to be used while still obtaining the desired densified sintered body.