A thin film dielectric composite has been produced consisting of lead-free barium titanate nanoparticles bound by the conformal atomic layer deposition of hafnia. The materials were examined crystallographically, topologically, and structurally using a variety of techniques including scanning electron microscopy and high-resolution transmission electron microscopy. Electrical measurements of capacitors using the composite material revealed dielectric constant variations of 200-1200 depending on the bias direction, corresponding to asymmetric leakage mechanisms and contributions from interface defects. Piezoresponse force microscopy indicated accessible polarization within the nanoparticles. This work illustrates an approach for conformally depositing a dielectrically tunable composite thin film with novel electrical properties.