Effects of K Nonstoichiometry in (Bi_0.5K_0.5+x)TiO₃ Ceramics

Abstract

K nonstoichiometry effects in (Bi_0.5K_0.5+x )TiO₃ (BKT) ceramics were studied with K contents varying in the range of −8≤ x ≤+1 mol% from the stoichiometric K_0.5. Within the range tested, a single BKT phase region was found to be at −1≤ x ≤+1 mol% and secondary phases started emerging with further K deficiency. Despite the formation of secondary phases, BKT perovskite with tetragonal symmetry was retained at all compositions. For nonstoichiometric BKT perovskite, a composition dependent structure property relation was observed; a decrease in tetragonality (c/a) caused piezoelectric coefficient (d ₃₃) enhanced while depolarization temperature (T_d ) reduced and vice versa.

Keywords:

• Pb-free bismuth potassium titanate
• piezoelectric coefficient
• depolarization temperature
• nonstoichiometry
• lattice distortion

Acknowledgment

This work was supported by the National Research Foundation of Korea Grant funded by the Korean Government (2009-0088570). This research was also financially supported by the Ministry of Education, Science and Technology (MEST) and Korea Institute for Advancement of Technology (KIAT) through the Human Resource Training Project for Regional Innovation.