Synthesis, crystal structure, dielectric properties, and potential use of nanocrystalline complex perovskite ceramic oxide Ba2ErZrO5.5

A new member belongs to Ba₂REZrO_5.5 (RE = Rare-Earth) perovskites, viz. Ba₂ErZrO_5.5, is synthesized as nanocrystals using a combustion process. Unlike the other Ba₂REZrO_5.5 perovskites, which are cubic, Ba₂ErZrO_5.5 crystallizes in tetragonal structure having space group P4/mnc (#128). Phase purity and ultrafine morphology of Ba₂ErZrO_5.5 powders were examined using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), Fourier transform of infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) specific surface area measurements, and transmission electron microscopy (TEM). Nanocrystals of Ba₂ErZrO_5.5 was sintered at ∼1500 °C for 4 h; whereas coarse-grained powders synthesized through solid state reaction could not be sintered even at 1700 °C for prolonged duration. XRD pattern of Ba₂ErZrO_5.5 was refined for atomic coordinates, lattice parameters, occupancies, and thermal factors using Rietveld analysis of XRD. Dielectric constant (?′) of Ba₂ErZrO_5.5 at 10 MHz is 21.62 ± 2 and dielectric loss (tan δ) is 5 × 10⁻³ at room temperature. Similar to the other Ba₂REZrO_5.5 perovskites, Ba₂ErZrO_5.5 is also showed chemically stability with YBa₂Cu₃O_7−δ (YBCO) and Bi₂Sr₂Ca₁Cu₂O_x (Bi-2212) superconductors. Ba₂ErZrO_5.5 can possibly be used as a substrate for high temperature superconductor (HTS) films, or be used as an insulator in the active superconductor-insulator-superconductor (SIS) structures.