Honey mediated microwave assisted sol–gel synthesis of stabilized zirconia nanofibers

Abstract

Aim of the present work is to prepare zirconia nanofibers using microwave assisted sol–gel method. Both honey and microwave powers are employed as structure directing agents to improve the stability and reduce the crystallite size. Honey, acting as capping agent, prevents the particles from hard agglomeration. Soft agglomeration or less agglomeration results in smaller crystallite size that prevents the transformation of tetragonal to monoclinic phase resulting in stabilized tetragonal zirconia (t-ZrO2). Zirconium oxychloride is used as precursor of zirconium and deionized water as solvent. Effect of microwave powers, in the range of 100–900 W with interval of 200 W, on zirconia stabilization is observed. X-ray diffraction analysis shows the presence of phase pure t-ZrO2 at low microwave power ~ 100 W with crystallite size ~ 26 nm. Formation of phase pure t-ZrO2 at low microwave power is due to the presence of sufficient amount of honey to coat the zirconia crystals. Relatively higher x-ray density has been observed in case of phase pure t-ZrO2 at 100 W of microwave power. This high density and phase purity reveals the high value of hardness (~ 1503 HV). Scanning electron microscopy analysis reveals the formation of well-separated nanofibers without agglomeration at 100 W. These nanofibers are purposed for bone implants and bone grafting. Structural transformation along with hard agglomeration is observed with increase in microwave powers from 500 W to 900 W. FTIR and Raman fundamental tetragonal bands, appearing at 490 cm−1 and 148 cm−1, respectively, confirm the formation of t-ZrO2 at low microwave power. Sample with phase purity exhibits high grain boundary resistance (1.95 MΩ) along with high dielectric constant (~ 74) and low tangent loss (at log f = 4.0). It is worth mentioning here that phase pure t-ZrO2 at very low microwave power (~100 W) with high density and well-separated nanofibers has been obtained without any post heat treatment.