Effect of Ba(Y1/2Nb1/2)O3 and BaZrO3 on the cation order and properties of Ba(Co1/3Nb2/3)O3 microwave ceramics

The effect of different solid solution additives and heat treatments on the cation order and dielectric properties of Ba(Co1/3Nb2/3)O3 (BCoN) were investigated. Pure Ba(Co1/3Nb2/3)O3 undergoes an order-disorder transition at about 1400 C, with the Q value of the ordered phase (Q.f = 64400) being significantly higher than the disordered variant (Q.f = 10800). The substitution of BaZrO3 destabilises the 1:2 order and a 1:1 ordered phase is formed for about 10-20 mol% BZ. The order-disorder temperatures for the 1:1 BCoN-BZ phases are quite low ( < 1300 C) and lead to lower degrees of order and lower Q values. The substitution of Ba(Y1/2Nb1/2)O3 (BYN) also induces a transition to 1:1 ordering, but in this case the stability of the order is significantly higher and the samples remain ordered to at least 1550 C. The greater degree of order in the BYN system is accompanied by higher Q values compared to their BZ counterparts. However none of the samples reach the Q values of the pure ordered BCoN end-member. 13 refs.