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Dielectric spectra of ceramic samples of Ca1−xPbxTiO3 (0⩽x⩽0.4) solid solutions were studied at frequencies between 10 Hz and 1 MHz in a temperature range of 4.2–300 K. A ferroelectric phase transition was observed at x=0.3 with transformation to a relaxor type behavior at x>0.3. The transition temperature Tc follows a linear dependence Tc∝(x−xc) with xc=0.28 contrary to a square-root dependence Tc∝(x−xc)1/2 predicted by the theory for incipient ferroelectrics. The critical concentration essentially exceeds the xc values for SrTiO3 and KTaO3 incipient ferroelectrics.

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Dielectric properties of ceramic samples of (1−x)SrTiO3–xSrMg1/3Nb2/3O3 and (1−x)SrTiO3–xSrSc1/2Ta1/2O3 solid solutions were studied at x⩽15% and x⩽10%, respectively. The real and imaginary parts of the dielectric constant were measured at frequencies between 10 Hz and 1 MHz and in a temperature range of 4.2–300 K. Remarkable relaxation was found between 80 and 300 K. The relaxation was suggested to be due to local charge compensation processes. The activation energy for these processes was determined to be (0.25±0.05) eV with τ0=(10−12…10−13) s.