Enhanced Tunability Achieving at Low Permittivity and Electric Field in (Ba(0.91)Ca(0.09))(Sn(x)Zr(0.2)(−)(x)Ti(0.8))O(3)-2 mol% CuO-1 mol% Li(2)CO(3) Ceramics

Ferroelectric varactors should have high tunability at low permittivity and a working electric field to obtain better impedance matching and stable tunability. In this work, (Ba(0.91)Ca(0.09))(Sn(x)Zr(0.2−x)Ti(0.8))O(3)-2 mol% CuO-1 mol% Li(2)CO(3) (abbreviated as BCSZT100x, x = 0.05, 0.10, 0.15 and 0.20, respectively) are prepared to achieve high tunability at low permittivity and a working electric field. The tunable mechanisms are investigated based on crystal structure, micro-morphology and the permittivity-temperature spectrum. The results show that the shrink of oxygen octahedron and weaker interaction force between Sn(4+) and O(2−) make BCSZT5 ceramic have a higher tunability value of 26.55% at low permittivity (1913) and a working electric field (7.3 kV/cm). The tunability value of BCSZT5 ceramic increases by 58%, while its permittivity decreases by 25%, compared with x = 0. Those advantages make BCSZT5 ceramic have substantial application prospects in varactors.