Method for manufacturing sensor element

A method for manufacturing a sensor element,

• the sensor element extending in a direction of an axial line, having a plate shape, and including
• a pair of electrodes,
• a ceramic layer having a hollow space that is to be an air introduction hole and that extends in the direction of the axial line, and
• a first layer and a second layer respectively stacked on both surfaces of the ceramic layer so as to cover the hollow space,
• one of the electrodes being in communication with the hollow space,
• the method comprising:
• a preparation step of preparing
• an unsintered ceramic sheet to be the ceramic layer after sintering, the unsintered ceramic sheet having a pre-sintering hollow space in a portion corresponding to the hollow space, and
• a burn-out material sheet having smaller dimensions than the pre-sintering hollow space when viewed in a plane direction of the unsintered ceramic sheet, the burn-out material sheet having a thickness different from that of the unsintered ceramic sheet, the burn-out material sheet having, in a plane orthogonal to the direction of the axial line, a cross-sectional area substantially identical to a cross-sectional area of the pre-sintering hollow space;
• a placement step of accommodating the burn-out material sheet inside the pre-sintering hollow space of the unsintered ceramic sheet;
• a pressing step of, after the placement step, pressing the unsintered ceramic sheet and the burn-out material sheet so as to have an identical thickness;
• and
• a sintering step of, after the pressing step, sintering the unsintered ceramic sheet and the burn-out material sheet to burn out the burn-out material sheet and make the unsintered ceramic sheet into the ceramic layer, thereby forming the hollow space.