Phase Boundary Shift by Thermal Strain in 100-Oriented Epitaxial Pb(ZrxTi1-x)O3 Film Grown on CaF2 Substrates

100-oriented epitaxial Pb(Zr,Ti)O 3 [PZT] films with various Zr/(Zr+Ti) ratios from 0 to 0.8 were grown on (100) c SrRuO 3 ∥(100) SrTiO 3 and (100) c SrRuO 3 ∥(100) LaNiO 3 ∥(001) CaF 2 substrates. 200-nm-thick films grown on CaF 2 substrates consisted of a pure tetragonal phase up to the Zr/(Zr+Ti) ratio of 0.8. On the other hand, the phase of the films on SrTiO 3 substrates changed from pure tetragonal below the Zr/(Zr+Ti) ratio of 0.4 to rhombohedral above the Zr/(Zr+Ti) ratio of 0.6 through their mixture phase within the Zr/(Zr+Ti) ratio range from 0.4 to 0.6. The larger polarization value was observed to be lager for PZT films on CaF 2 substrates than for PZT films on SrTiO 3 substrates for all Zr/(Zr+Ti) ratios and was in good agreement with the estimated one assuming tetragonal symmetry. The tetragonal region can be expanded to a Zr/(Zr+Ti) ratio of 0.8 below 1 µm in thickness for films on CaF 2 substrates. The present results show that the large thermal strain induced by CaF 2 substrates having with a large thermal expansion coefficient can expand the tetragonal symmetry region up to large a Zr/(Zr+Ti) ratio and thicker films.