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

In this work, cyclotetravanadate Na2SrV4O12 was synthesized at a relatively low sintering temperature of similar to 500 degrees 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 (V4O12)(4-). Dielectric measurements demonstrated strong dependence on frequency and temperature. A low relative permittivity of epsilon(r) similar to 8 +/- 0.2 and a dielectric (loss tan delta) similar to 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 V5+ to V4+), 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 Na2SrV4O12 ceramic a potential candidate for lightweight devices and in photocatalytic degradation and all-solid-state ion batteries.