The Effect of Y Addition on Morphology, Structure, and Electrical Properties of Yttria-Stabilized Tetragonal Zirconia Dental Materials.

Zirconia (ZrO), a widely known material with an extensive range of applications, is especially suitable for dental applications. This kind of dental material is produced in the form of blocks or discs (mostly discs-depending on CAD/CAM machines) by cold isostatic pressing (CIP). Such discs are subsequently milled by CAM/CAD technology into a desirable form. Due to the application of CIP, the resulting discs consist of different yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) powders, additives and pigments. The diverse composition of the discs (e.g., different Y content) governs material properties, such as hardness, toughness and translucence. The aim of this work was to investigate the impact of Y addition on the grains and grain boundaries, on the ZrO phases lattice parameter values and on the electrical equivalent circuit parameters of the prepared Y-TZP samples. The disc-shaped samples were prepared by using CAM/CAD technology. It was observed that the grain size and the grain density were increased by Y addition. The sample with the lowest Y content was characterized by the highest portion of the tetragonal phase, whilst the disc with the highest Y addition consisted mainly of the cubic phase. It was also observed that at the higher Y ion concentrations, these ions mainly incorporated the tetragonal phase. Furthermore, conductivity investigations showed that the resistivity of the grains in the samples with the higher Y concentrations was decreased as these ions were mainly trapped in the grain boundary. On the other hand, the Y trapping increased the capacitance of the grain boundary.