PTCR properties and aging characteristics in Y2O3 doped BaTiO3 ceramics with ZrO2 additions

The effects of yttria and zirconia additions to the BaTiO₃ microstructure and the positive temperature coefficient of resistance (PTCR) effect are studied. Y₂O₃ and ZrO ₂ were added to barium- and titanium-rich samples without the incorporation of SiO₂, so that only the effects of each could be observed. Several aging studies were used to determine the type of changes which occur from added ZrO₂. The stoichiometry was varied using Ba/Ti=1.003 and 0.997. Small ZrO₂ additions to the Ti excess materials greatly affected the microstructures and within the limit of solubility lowered the resistivity by up to an order of magnitude and increased the rise at the Curie temperature (T _c). ZrO₂ additions degraded the PTCR properties for Ba excess samples. Various static and cyclic modes of aging were used to study the resistivity instability. ZrO₂ additions were found to improve the degradation in resistivity in Ti excess materials. Without added ZrO₂ the Ba excess materials showed smaller variations in resistivity in all modes