In-situ observation of nanomechanical behavior arising from critical-temperature-induced phase transformation in Ba(Zr0.2Ti 0.8)O3-0.5(Ba0.7Ca0.3)TiO 3 thin film

In this Letter, we use the nanoindentation technique and vary the testing temperature to above and below critical values to study the nanomechanical features of a strong Pb-free piezoelectric Ba(Zr0.2Ti 0.8)O3-0.5(Ba0.7Ca0.3)TiO 3 (BZT-0.5BCT) thin film across its piezoelectric-optimal morphotropic phase boundary. The mechanisms responsible for the Young's modulus and hardness evolution are then discussed. An X-ray diffraction method that can detect the d(110) variation associated with the change in the inclination angle ψ of the (110) plane was developed to quantify the residual stress in the BZT-0.5BCT films.