10.1016/j.solidstatesciences.2016.09.005
Dielectric properties of FeNbO4 ceramics prepared by the sol-gel method

FeNbO4 powders were prepared using the sol-gel method. Niobium chloride (NbCl5) and iron nitrate (Fe(NO3)3*9H2O), were used as starting materials and citric acid and ethylene glycol as chelating agent and reaction medium, respectively. A suspension containing stoichiometric amounts of starting materials was previously prepared in a minor amount of hydrogen peroxide (3% V/V) and dispersed in a mixture of citric acid and ethylene glycol in a molar ratio 1:3. In order to promote the solubility, the suspension was stirred until a clear colloidal suspension was obtained. 

The solution was dried at 300 degC for 24 h to evaporate the solvent and the obtained powders were thermally analysed by differential thermal analysis, performed in a Lynseis Apparatus type L92/095, in the temperature range 20-1200 degC, with a heating rate of 5 degC/min, using Al2O3 as reference. 

Subsequently, the dry powders were pressed into pellets, and finally heat-treated, according to the DTA results, at 500, 650, 850, 1000 and 1200 degC, using a dwell time of 4 h, with a heating rate of 5 oC/min.
suspension
hydrogen peroxide
3% V/V
% V/V
citric acid and ethylene glycol
molar ratio
1:3
powders were thermally analysed
temperature range
20-1200 degC
degC
powders
heating rate
5 degC/min
degC/min
solution
dried
300 degC
degC
solution
dried
24 h
h
pellets
heat-treated
500, 650, 850, 1000 and 1200 degC
degC
pellets
heat-treated
4 h
h
pellets
heating rate
5 oC/min
oC/min