Lead magnesium niobate $[Pb(Mg_\frac{1}{3}Nb_\frac{2}{3})O_3]$ is a relaxor ferroelectrics with a disordered perovskite structure. It was known that a statistical inhomogeneity in the distribution of $Mg^{2+}$ and $Nb^{5+}$ ions in the B-sites of an $ABO_3$ perovskite lattice leads to a wide Curie temperature range and relaxor ferroelectric characteristic. With 10 mol % $PbTiO_3$ substitution its Curie temperature, dielectric constant and strain by electric field is increased so applicable to not only high permittivity capacitor but also electrostrictive actuator. Nearly pyrochlore-free perovskite structure was obtained by columbite precursor method and double calcination. From TEM selected area diffraction patterns it is certain that ordering in B-site ions is partially formed and microinhomogeneity like that comprises relaxor characteristic. As sintering temperature rises, grain size and dielectric constant increase without appreciable change of density. And the intensity of ordering spot brightens relatively. The dielectric constant change with sintering temperature is due to grain size effect and change of short range ordering.
