Synthesis, crystal structure, and characterization of Na₂SrV₄O₁₂: A low‐firing dielectric vanadate

Abstract

In this work, cyclotetravanadate Na 2 SrV 4 O 12 was synthesized at a relatively low sintering temperature of ∼500 • C using a solid-state reaction method. X-ray diffraction and a transmission electron microscope characterization featured a tetragonal structure that was built by a 3D frame of isolated tetracyclic (V 4 O 12 ) 4− . Dielectric measurements demonstrated strong dependence on frequency and temperature. A low relative permittivity of ε r ∼ 8 ± 0.2 and a dielectric (loss tanδ) ∼ 0.4 ± 0.01 was achieved at a frequency of 10 kHz and room temperature. ac impedance and conductivity analysis revealed a thermally activated migration behavior of charge carriers with a short-range hopping feature. XPS analysis validated the existence of oxygen vacancy and reduction in vanadium (from V 5+ to V 4+ ), which gave rise to charged lattice defects. The migration or hopping of such charged defects was responsible for the observed electrical behaviors. Owing to the simple composition, inexpensive raw materials and low density (2.99 g/cm 3 ) make Na 2 SrV 4 O 12 ceramic a potential candidate for lightweight devices and in photocatalytic degradation and all-solid-state ion batteries.