High-voltage varistor materials were prepared using an ultrafine additives precursor obtained from the precipitation method. Microstructural and electrical studies showed that the sample exhibited a smaller average grain size (d=4.5 mu m) and a considerably higher breakdown voltage (E(b)=1610 +/- 30 V/mm) as compared with the conventional one (d=6.5 mu m, E(b)=400 +/- 30 V/mm). The high voltage is attributed to the improvement in microstructure homogeneity and the formation of more active grain boundaries per unit volume. This novel route may explore the commercial possibility of device miniaturization.