A series of (100$-x)$Pb(Mg${}_{1/3}$Nb${}_{2/3})$O${}_3-x$PbTiO₃ (PMN$-x$PT, $x$= 24, 25, 26) ceramics were prepared by solid-state reaction technique using MgNb₂O₆ precursor. The results of the detailed characterizations reveal that the content of PT has negligible influence on the grain size, and all samples possess the perovskite structure. As the PT content increases, the samples changed from the normal ferroelectric phase to the ergodic relaxor state at room temperature. As a result, PMN–$x$PT ceramics are endowed with electro-strain of 0.08% at a relatively low electric field of 2 kV/mm, and effective piezoelectric coefficient of 320 pm/V was obtained. Simultaneously, the PMN–$x$PT ceramics have exceptional pyroelectric performance, exhibiting a high pyroelectric coefficient $p$$\sim$5.5 – 6.3 × 10${}^{-8}$ C⋅cm${}^{-2}$⋅K${}^{-1}$. This study demonstrates the great potential of PMN–$x$PT for piezoelectric and pyroelectric device applications.A series of (100$-x)$Pb(Mg${}_{1/3}$Nb${}_{2/3})$O${}_3-x$PbTiO₃ (PMN$-x$PT, $x$= 24, 25, 26) ceramics were prepared by solid-state reaction technique using MgNb₂O₆ precursor. The results of the detailed characterizations reveal that the content of PT has negligible influence on the grain size, and all samples possess the perovskite structure. As the PT content increases, the samples changed from the normal ferroelectric phase to the ergodic relaxor state at room temperature. As a result, PMN–$x$PT ceramics are endowed with electro-strain of 0.08% at a relatively low electric field of 2 kV/mm, and effective piezoelectric coefficient of 320 pm/V was obtained. Simultaneously, the PMN–$x$PT ceramics have exceptional pyroelectric performance, exhibiting a high pyroelectric coefficient $p$$\sim$5.5 – 6.3 × 10${}^{-8}$ C⋅cm${}^{-2}$⋅K${}^{-1}$. This study demonstrates the great potential of PMN–$x$PT for piezoelectric and pyroelectric device applications.