Pb(B0.5Nb0.5)O3 (B = Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) powders were prepared from mixed nitrate solutions by a chemical coprecipitation method. This method produced very small particles (∼30 nm) with good compositional homogeneity. These powders were highly reactive upon calcination. The powders of the systems (B = Sc, Tm, Yb and Lu) yielded ∼100% perovskite phase after calcination between 800°C and 1000°C for 1 h. For the system with B = Er, 93% perovskite phase was formed at 900°C for 1 h. For the other systems of the elements (B = Y, Nd, Sm, Eu, Gd, Tb, Dy and Ho) with a larger ionic size, perovskite compounds were not formed up to 1100°C. The stability and the possible formation of the compounds with a perovskite structure for the Pb(B0.5Nb0.5)O3 series were discussed.