“…BST thin films have also been widely investigated for microwave applications such as phase shifters, tunable filters, tunable resonators, and switches [26][27][28][29][30]. Metal ion-doped BST samples, including thin films and ceramics, have also been investigated [31][32][33][34][35][36][37][38]. Especially, concerning Fe-doped Ba x Sr 1 À x TiO 3 samples, the overwhelming majority focus on BSTF thin films [34][35][36][37][38].…”