Polymorphic phase transition and enhanced piezoelectric properties in (Ba0.9Ca0.1)(Ti1−xSnx)O3 lead-free ceramics

► We achieve enhanced piezoelectricity in (Ba0.9Ca0.1)(Ti1−xSnx)O3 ceramics. ► We used the different functions of Sn4+ and Ca2+ to enhance properties. ► Our work could promote the research of (Ba,Ca)(Ti,Sn)O3 systems.