Microwave field: Temperature-dependent dielectric properties and heating characteristics during the synthesis of alpha-tellurium dioxide

Abstract

The temperature-dependent dielectric properties of the precursor can provide theoretical support for microwave synthesis related materials. Herein, temperature-dependent dielectric properties and microwave heating characteristics were researched in detail during the synthesis of alpha-tellurium dioxide (α-TeO2) by a microwave removal of hydrogen from orthotelluric acid (H6TeO6). The results showed that the dielectric constant (εr′) and the dielectric loss (εr″) values of H6TeO6 were divided into six stages due to the evolution of the structure with increasing temperature. And the loss tangent coefficient (tanδ) values had two distinct wave crests: 200–400 °C, and 450–600 °C, which corresponded to maximum tanδ values of 0.044 (F/m) at 350 °C and 0.028 (F/m) at 550 °C, respectively. In addition, TG-DSC, XRD, FT-IR, SEM were employed to track the as-synthesized evolution of structure and morphology during calcination. The results indicated that the fine and uniform α-TeO2 particles could be obtained by the microwave treatment at 600 °C for 10 min. The work not only provides a stable and high-quality precursor for the application of α-TeO2, but also offers theoretical data support for microwave preparation and design of tellurium oxide-based materials.