large grain size, giving rise to less degradation of the frequency dependence polarization and strain. This occurs because the internal random fields created by the seed, slow down the effect of a reversion of induced long-range ferroelectric ordering to short-range ordering of relaxor phase with the frequency.

The frequency-related electromechanical properties of r-ST26-ST10 and t-ST26-ST10 composites at different soaking times were investigated. ST26 composite ceramics with different sizes of the ferroelectric seed ST10 were successfully synthesized by a conventional solid-state reaction and molten-salt method. The polarization and electric field-induced strain increased with only 10% addition of seeds to the matrix and overall decreased with the increasing soaking time for t-ST26-ST10 and r-ST26-ST10. The degradation of the polarization and electric field-induced strain with the frequency was investigated in detail. The critical composition, ST26-ST10 with 10% seed in the composite, resulted in a high P~r~, S~max~, and d~33~\* values with an enhanced phase transition. From the study of the polarization and strain with the frequency, a ferroelectric addition prompted the stability corresponding to the coexistence of FE (seed) and RE (matrix) phases in a composite. The electromechanical properties of the composites increased until the optimum composition and soaking time for the 10% large grain size seed content was reached, and then, they gradually decreased and changed to the FE phase with the increased soaking time of the composite, driving the absorption of the two phases in the ABO~3~ perovskite structure. The decreasing trend of the activation energy calculated using the KAI relationship suggests that a faster domain velocity was generated by increasing the seed content in a ST26 matrix. This result suggests that the ST26 composite is a promising candidate for Pb-free electromechanical applications.

Material and Methods {#Sec4}
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Sample Preparation {#Sec5}
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