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In order to obtain a diphasic ceramic composite consisting of Pb(Zr, Ti)O_3(PZT) and PbTiO_3, the following experiment was carried out. Raw materials were (1) Bi_2O_3-and Pb(W_<1/2>Ni_<1/2>)O_3-modified PZT powder with a composition near the morphotropic phase boundary and average particle size of 0.6 μm, pure PbTiO_3 powders with average particle size of (2) 5 μm and (3) 20μm. These powders were mixed at PZT/PbTiO_3 mass ratios of 75/25, 50/50 and 25/75, pressed into disks and then fired at around 1000℃ for 0.5h (short-time soak) or 12h (long-time soak). The short-time-soaked compact with PZT/PbTiO_3(20 μm) mass ratio of 32.5/67.5 was hot-isostatically pressed (HIPed) at 1000℃ and 200 MPa in O_2(5%)/Ar gas atmosphere for 1h without encapsulation. PZT/PbTiO_3 diphasic ceramic composites were obtained at PZT/PbTiO_3 mass ratios of 50/50 and 25/75 for (a) short-time soak (0.5h) with 5 μm and 20 μm PbTiO_3 powders and (b) long-time soak (12h) with 20 μm PbTiO_3 powder, although their relative densities were 50-70%. The HIPed compact was a PZT/PbTiO_3 diphasic ceramic composite with 95% relative density. The composition of the reacted PZT in the ceramic composite was shifted to the tetragonal (Ti-rich) side from that of starting PZT powder and compositional fluctuation was observed, while that of PbTiO_3 was not detected by X-ray analysis.