Compositional dependence of Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3 piezoelectric thin films prepared by combinatorial sputtering

• Compositional gradient BZT–BCT thin films were deposited by combinatorial sputtering.
• The maximum relative dielectric constant (εr = 778) was obtained for x = 0.50.
• The piezoelectric coefficients |e31, f| reached to 0.48 C/m2 at around x = 0.50.

In this study, we evaluate the compositional dependence of Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3 (BZT–BCT) thin films prepared by combinatorial sputtering. Compositional gradient polycrystalline (1 − x)BZT–xBCT thin films oriented along the < 001 > and < 111 > directions were deposited on Si substrates by co-sputtering BZT and BCT targets and the composition x was varied from 0.16 to 0.82. Over the whole composition range, the BZT–BCT thin films exhibited smooth surfaces and columnar structure. The temperature dependence of the dielectric properties was measured and the tricritical phase transition point of BZT–BCT thin films was determined to be the same composition as that of bulk ceramics, while its temperature was approximately 100 °C higher. The maximum relative dielectric constant (εr = 778) was obtained for x = 0.50. The piezoelectric coefficients also peaked at around x = 0.50, and the maximum value (|e31, f| = 0.48 C/m2) was compatible with other Ba-based piezoelectric epitaxial thin films. These results indicate that polycrystalline BZT–BCT thin film is a promising material as a substitute for lead-based piezoelectric materials.