FIG. 1 is a perspective view showing a stacked ceramic capacitor as the background art of the present invention, and FIG. 2 is an illustration diagram showing an internal structure thereof. A stacked ceramic capacitor 10 includes a ceramic body 12 having, for example, a rectangular parallelepiped shape. Ceramic body 12 includes a plurality of stacked dielectric ceramic layers 14. An internal electrode 16 is formed at an interface between these dielectric ceramic layers 14. Internal electrodes 16 face and overlap with each other at a central portion of ceramic body 12, and adjacent internal electrodes 16 are alternately led out to two end surfaces of ceramic body 12 that face in the longitudinal direction. An external electrode 18 is formed at the end surface of ceramic body 12 to which internal electrodes 16 are led out. Internal electrodes 16 led out to the respective end surfaces of ceramic body 12 are connected to two external electrodes 18. Therefore, adjacent internal electrodes 16 are alternately connected to two external electrodes 18 and a capacitance is formed between these external electrodes 18.
In order to fabricate stacked ceramic capacitor 10 described above, a ceramic slurry is formed by using a dielectric ceramic composition. This ceramic slurry is formed into a sheet shape, thereby forming a ceramic green sheet 20. As shown in FIG. 3, a plurality of internal electrode patterns 22 are formed on ceramic green sheet 20 by using a conductive paste. Ceramic green sheets 20 each having internal electrode patterns 22 are stacked, and on both sides thereof, ceramic green sheets 20 each having no internal electrode patterns are stacked as needed. Stacked ceramic green sheets 20 are pressure-bonded and a mother stacked body 24 is formed.
Mother stacked body 24 is cut and a crude stacked body chip having adjacent internal electrode patterns 22 exposed alternately to both end surfaces is formed. This stacked body chip is fired, thereby forming ceramic body 12 having dielectric ceramic layers 14 and internal electrodes 16. An electrode paste is applied and baked onto the end surface of ceramic body 12 to which internal electrodes 16 are exposed, thereby forming external electrode 18. External electrode 18 is plated as needed.
When such stacked ceramic capacitor 10 is used in, for example, a vehicle-mounted application, stacked ceramic capacitor 10 may sometimes be arranged near an engine. In such a case, the temperature around stacked ceramic capacitor 10 changes greatly, and a dielectric constant of dielectric ceramic layers 14 changes in accordance with the aforementioned temperature change, and a capacitance of stacked ceramic capacitor 10 changes in accordance therewith. However, needless to say, stacked ceramic capacitor 10 having a small rate of change in capacitance with respect to the temperature change is preferable.
Thus, disclosed is a dielectric material in which a capacitance-temperature change rate in a range of −55° C. to 250° C. becomes ±15% by adding BaO, MgO and Nb2O5 to an alkali niobium-based material (K, Na, Li)(Nb, Ta)O3 (refer to PTD 1).
PTD 1: Japanese Patent Laying-Open No. 2009-249244