  Lead-free materials based on the $\text{(Ba,Ca)(Zr,Ti)O}_{3}$ (BCZT) system
exhibit excellent electromechanical properties that can be strongly modified by
small amounts of dopants. Here, we use a high throughput strategy to unravel
the influence of aliovalent doping with Ce on dielectric and piezoelectric
properties of BCTZ. We synthesize and characterize a single BCTZ thin film with
a composition gradient from undoped to 0.2 mol % cerium doping. The cerium
doping increases the piezoelectric coefficient from $42.3\pm 2.9 \text{pm
V}^{-1}$ (undoped) to $63\pm 2.4 \text{pm V}^{-1}$ for 0.06 Ce-mol\%, and then
decreases to $38.4 \pm 1.3 \text{pm V}^{-1}$ for the maximum amount of cerium
(0.2 mol %). An investigation of sub-coercive field non-linearities reveal that
these variations are not only induced by changes in dynamics and densities of
domain walls. The results highlight the advantage of high throughput techniques
to identify ideal compositions for applications, without synthesizing a high
number of samples with unavoidable sample-to-sample variations.
