Uniaxial stress dependence of the dielectric permittivity of the Na0.5Bi0.5TiO3–KTaO3 system

The dependence of the dielectric permittivity on the uniaxial compressive stress was investigated for the case of Na0.5Bi0.5TiO3–KTaO3 ceramics. Special attention was focused on the reversibility of the permittivity–stress dependence. The results were connected with the transition from the ferroelectric to the relaxor state in the concentration region between 5 and 10 mol% of KTaO3. With this transition, the permittivity–stress dependence changes from non-linear, irreversible and time dependent to linear, instantaneous and reversible. In samples with 10–30 mol% of KTaO3 some minor relaxations were observed, which were suppressed under a small pre-stress. The stress sensitivity was higher at a lower measuring frequency and the reversible change of the permittivity was the highest in the sample with 20 mol% of KTaO3 (the absolute and relative changes of permittivity were 196.5 and 10.3%, respectively, at a pressure change between 8 and 219 MPa). The obtained results are discussed in terms of the macrodomains/microdomains’ reorientation under applied pressure and the transition from one to another with a change of the KTaO3 concentration. The use of Na0.5Bi0.5TiO3–KTaO3 ceramics for device applications is described.

► Lead-free Na0.5Bi0.5TiO3–KTaO3 materials for pressure sensing.
► Dielectric permittivity–uniaxial stress dependence.
► Change in the permittivity–stress dependence with change in domain structure.
► Instantaneous and reversible dependence in relaxor compositions.