Characterization and dielectric properties of Ba5LnNiTa9O30 (Ln = La, Nd and Sm) ceramics

Three novel Ba₅LnNiTa₉O₃₀ (Ln = La, Nd and Sm) ceramics were prepared and characterized in the BaO-Ln₂O₃-NiO-Ta₂O₅ system. All three compounds adopted the filled tetragonal tungsten bronze (TB) structure at room temperature. The present ceramics exhibited relaxor behavior, and the Curie temperature (at 10kHz) were −130, −80 and −45°C for Ba₅LaNiTa₉O₃₀, Ba₅NdNiTa₉O₃₀, and Ba₅SmNiTa₉O₃₀ respectively. At room temperature, Ba₅LnNiTa₉O₃₀ ceramics have a high dielectric constants in the range 102∼118, a low dielectric loss in range 0.0019∼0.0036, and the temperature coefficients of the dielectric constant (τ_ɛ) in the range −320∼−460 ppm°C⁻¹ (at 1 MHz).