Low temperature properties of ${\mathrm{BaZrO}}_3$ are revealed by combining experimental techniques (x-ray diffraction, neutron scattering and dielectric measurements) with theoretical first-principles-based methods (total energy and linear response calculations within density functional theory, and effective Hamiltonian approaches with and without zero-point vibrations). Unlike most of the perovskite systems, ${\mathrm{BaZrO}}_3$ does not undergo any (long-range-order) structural phase transition and thus remains cubic and paraelectric down to 2 K, even when neglecting zero-point vibrations. On the other hand, these latter pure quantum effects lead to a negligible thermal dependency of the cubic lattice parameter below $\simeq 40\mathrm{K}$. They also affect the permittivity of ${\mathrm{BaZrO}}_3$ by inducing an overall saturation of the real part of the dielectric response, for temperatures below $\simeq 40\mathrm{K}$. Two fine structures in the real part, as well as in the imaginary part, of the dielectric response are further observed around 50–65 K and 15 K, respectively. Microscopic origins (e.g., unavoidable defects and oxygen octahedra rotation occurring at a local scale) of such anomalies are suggested. Finally, possible reasons for the facts that some of these dielectric anomalies have not been previously reported in the better studied ${\mathrm{KTaO}}_3$ and ${\mathrm{SrTiO}}_3$ incipient ferroelectrics are also discussed.

• Received 11 March 2005

DOI:https://doi.org/10.1103/PhysRevB.72.205104