Abstract: A new route was developed for preparation of nonreducible BCTZ ceramics.In this route, complex oxide dopants were obtained by sol-gel process ~via~ heat treatment at 500～
800℃, and then mixed and milled with (Ba_1-xCa_x)(Ti_1-yZr_y)O₃ powders to get nonreducible BCTZ ceramic powders, which could be fired
under reducing atmospheres to get base metal compatible ceramics with high permittivity and low dielectric loss. The influence of synthesizing
temperature of the mixed dopants, sintering temperature and annealing time on the microstructure and dielectrical properties of the BCTZ ceramics was studied. The
nanosized complex oxide dopants(nanosized dopants) synthesized at low temperature were confirmed to be suitable for the modification of the
ultrafine ceramic powders. With the increase of the synthesizing temperature of the complex oxide dopants at 500～800℃, the Curie
point, dielectric loss and dielectric maximum K_MAX of the BCTZ ceramics decreased. Studies on the firing process confirmed that nonreducible BCTZ ceramics
satisfying the Y5V specification could be prepared via this route. The ceramics had relative dielectric permittivity higher than 18000,
dissipation factor below 0.7%, resistivity as high as 10¹²Ω·cm, Curie point in the range of 5～20℃, and the average grain
size less than 4μm. This route can be hopeful to be adopted in the production of Y5V Ni-MLCC with large capacitance.

Key words: MLCCs, BCTZ ceramics, complex oxide dopants, sol-gel, dielectric properties, annealing