An electric field temporarily strengthens zirconia ceramics

By applying an electric field to yttria-stabilized zirconia (8YSZ) equipped with an inert electrode, oxide ions are localized near the positive electrode, causing it to expand. When polarization was performed under different conditions, it was possible to strengthen the material to 1.5 times that of an untreated sample. The lattice constant of the positive electrode surface after polarization was larger than before polarization. When the Vickers hardness of the positive electrode surface was measured by changing the test load, the smaller the load, the higher the hardness value. Polarization caused oxide ions to move near the positive electrode, filling in the defects and generating an expanded layer with a large lattice constant. It is believed that this was subjected to compressive stress from the bulk layer, which had not changed in volume, resulting in an increase in strength.