Effect of Stoichiometry on the Dielectric Properties and Life Performance of (Pb 0.875 Ba 0.125 ) [(Mg 1/3 Nb 2/3 ) 0.5 (Zn 1/3 Nb 2/3 ) 0.3 Ti 0.2 ]O 3 Relaxor Dielectric Ceramic: Part I, Dielectric Properties

Effects of stoichiometry (A/B mole ratio, i.e., the ratio of elements on the A‐site to those on the B‐site in the perovskite structure) on the dielectric properties and microstructure of a partially A‐site substituted relaxor, (Pb 0.875 Ba 0.125 ) A [(Mg 1/3 Nb 2/3 ) 0.5 (Zn 1/3 Nb 2/3 ) 0.3 Ti 0.2 ] B O 3 were investigated in the A/B range between 0.95 and 1.05. Specimens, with A/B equal to or greater than 1.01, were sintered at lower temperatures than those with A/B equal to or less than 1.00. A maximum dielectric constant (K max ) value of 13300 was obtained when A/B was 1.01. When A/B was less than 1.01, K max decreased, due to the formation of pyrochlore phase. K max also decreased with A/B values greater than 1.01, probably due to a grain boundary phase. Resistivity measurements did not suggest a stoichiometry dependence. However, breakdown voltage decreased with an increase in A/B, possibly due to the segregation of PbO with low dielectric constant at grain boundaries.