Effect of Stoichiometry on Mechanical Properties of (Pb_0.875Ba_0.125)[(Mg_1/3Nb_2/3)_0.5(Zn_1/3Nb_2/3)_0.3Ti_0.2]O₃ Relaxor Dielectric Ceramic

<jats:p>The mechanical and thermal properties of a partially A‐site‐substituted relaxor dielectric ceramic, (Pb<jats:sub>0.875</jats:sub>Ba<jats:sub>0.125</jats:sub>)A[(Mg<jats:sub>1/3</jats:sub>Nb<jats:sub>2/3</jats:sub>)<jats:sub>0.5</jats:sub>(Zn<jats:sub>1/3</jats:sub>Nb<jats:sub>2/3</jats:sub>)<jats:sub>0.3</jats:sub>Ti<jats:sub>0.2</jats:sub>]<jats:sub><jats:italic>B</jats:italic></jats:sub>O<jats:sub>3</jats:sub>, were investigated for specimens with <jats:italic>A/B</jats:italic> ratios ranging from 0.95 to 1.05. Vickers hardness, fracture toughness, and three‐point bending strength altered significantly at an <jats:italic>A/B</jats:italic> value between 1.00 and 1.01; this was accompanied by a change in the fracture mode from transgranular for <jats:italic>A/B</jats:italic># 1.00 to intergranular for 1.01 $<jats:italic>A/B</jats:italic>. The three‐point bending strength of the relaxor was twice the thermal stress predicted by a simulation of multilayer ceramic capacitors (MLCs) subjected to heat‐cycle tests. However, the tensile strength in the direction normal to the internal electrode layers was much less than the simulated thermal stress. This indicated that mechanical strength was not a critical problem as regarded the MLC dielectric material but, rather, that it was critical to improve the adhesion between dielectric layers and internal electrode layers. Results also showed that it was important to improve the termination structure and solder wettability at the termination.</jats:p>