The Electrical Conductivity of Giniite Fe5(PO4)4(OH)3·2H2O Materials.

Using the hydrothermal method, the iron hydroxyl phosphate materials Fe5(PO4)4(OH)3·2H2O (giniite), with an orthorhombic crystal structure were obtained. SEM analysis showed that the morphology of these iron hydroxyl phosphates is influenced by the pH of the aqueous solution from the hydrothermal synthesis: for pH=1.5 (Sample A) the shape of particles is spherical and by increasing the pH to 4.5 (Sample B) the particles transforms into dendrites. The electrical conductivity σ of these two giniite samples was studied in 20 Hz to 2 MHz frequency range at room temperature. The results show that the spectrum of σ conductivity, presents two regions: i) a first region, where σ remains constant at low frequency (the σDC component) and ii) a dispersion region, where the σ increases with increasing the frequency (the σAC component). For both samples, at the frequency f=1 kHz, the temperature dependence of conductivity (σ) and resistivity (ρ) at the variation of temperature between 25 °C to 200 0C, have been analyzed. The results show that the slope of ρ, changes with the increase of temperature at two temperatures, between (60-80) °C and respectively (160- 170) °C, which may be associated with changes in the structure of giniite samples, due to loss of water molecules by increasing of temperature. [ABSTRACT FROM AUTHOR]