Nd₂Ba₂CaZn₂Ti₃O_14.4: a new high dielectric constant oxide having a disordered (cubic) perovskite structure

Abstract

A new oxide of the formula Nd₂Ba₂CaZn₂Ti₃O_14.4 has been successfully prepared by a high-temperature ceramic route at 1200 °C. The title compound crystallizes in a cubic structure with a = 3.94263(7) Å (space group = Pm3m, wRp = 0.0305, Rp = 0.0192) as obtained from Rietveld refinement of powder neutron diffraction data. X-ray and electron diffraction studies also confirm the absence of any ordering of the cations. The title compound has a high dielectric constant of 59 at 100 kHz and a very small frequency coefficient of the dielectric constant (dε/dF = 1.26 × 10⁻⁶ Hz⁻¹). The dielectric loss is 0.0047 at 100 kHz, which also shows very minor variation with frequency. The temperature-dependence studies show an increase in dielectric constant and dielectric loss over the temperature range 35-300 °C.