Abstract: A sensor element (100) including: a detection element portion (300) provided with at least one cell (130, 140) having a solid electrolyte (105, 109) and a pair of electrodes (104, 106, 108, 110) disposed on the solid electrolyte; a measurement chamber (107c) faced by one of the electrodes; and a diffusion resistance portion (115) through which a gas to be measured is introduced from outside into the measurement chamber. The sensor element further includes a porous protection layer (21) that is in direct contact with the diffusion resistance portion and which at least covers the diffusion resistance portion. The porous protection layer contains ceramic particles which serve as a backbone, and has pores formed in gaps between the ceramic particles. Further, a diameter ratio R represented by (an average diameter D1 (nm) of the pores / a particle diameter D2 (nm) at which an accumulated number of the ceramic particles accounts for 50%) is not greater than 100.

Abstract: A holding device includes a ceramic member and a base member joined together via a joining portion. When a second direction is perpendicular to a first direction and a third direction is perpendicular to the first and second directions, the joining portion includes a first joining part which extends through the joining portion in the second direction, as viewed in the first direction, and whose thickness in the first direction is uniform in an arbitrary cross section perpendicular to the second direction and in an arbitrary cross section perpendicular to the third direction, and at least one second joining part which is located between the first joining part and one end of the joining portion in the third direction and whose thickness in the first direction increases from the first joining part side toward the end of the joining portion in an arbitrary cross section perpendicular to the second direction.

Abstract: A holding device includes a ceramic member and a base member joined together via a joining portion. When a second direction is perpendicular to a first direction and a third direction is perpendicular to the first and second directions, the joining portion includes a first joining part which extends through the joining portion in the second direction, as viewed in the first direction, and whose thickness in the first direction is uniform in an arbitrary cross section perpendicular to the second direction and in an arbitrary cross section perpendicular to the third direction, and at least one second joining part which is located between the first joining part and one end of the joining portion in the third direction and whose thickness in the first direction increases from the first joining part side toward the end of the joining portion in an arbitrary cross section perpendicular to the second direction.

Abstract: A holding device manufacturing method includes a step of preparing a first joined body which includes a pre-machining ceramic member having a first surface and a fifth surface located opposite the first surface and approximately parallel to the first surface, a base member, and a joining portion disposed between the first surface of the pre-machining ceramic member and a third surface of the base member and joining the pre-machining ceramic member and the base member together. The thickness of the joining portion of the first joined body in a first direction, in which the first surface and the third surface face each other via the joining portion, increases from one end side toward the other end side of the joining portion in a second direction perpendicular to the first direction. The method includes a step of machining the fifth surface of the pre-machining ceramic member in the first joined body.