Grain oriented ceramics constituted of a polycrystalline body having a first perovskite-type alkali-pentavalent metal oxide compound as the main phase, in which a specific crystal plane of each grain constituting the polycrystalline body is oriented. The materials that produce the release properties are incorporated in the plastic layer and can be extruded with it. The use of SH rather than RH decouples humidity from temperature and thus simplifies control of both. An optical intensity measuring unit measures the optical intensity of the first polarization component.