A large number of lead-free BaTiO₃-based ceramics were prepared. Depending on the composition, some of them exhibit a relaxor behaviour whose characteristics were related to the type of ionic substitution and to the substitution rate. The relaxor effect is all the more favoured as the composition deviates more from BaTiO₃ and as the substitution is heterovalent in the 6-coordination number crystallographic site. Some of these materials could prove valuable (dielectrics for capacitors and actuators) because they are environment-friendly.