Study of the hyperfine structure, thermal stability and electric–dielectric properties of vanadium iron phosphate glasses

• Published in: Physica. B, Condensed matter Condensed matter, 2009-07, Vol.404 (14), p.2058-2064
• Main Authors: Shapaan, M., Shabaan, E.R., Mostafa, A.G.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conductivity of specific materials; Dielectric properties of solids and liquids; Dielectric relaxation; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Disordered solids; Electric transport properties; Electronic transport in condensed matter; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Glass transition temperature; Glass transitions; ME spectroscopy; Permittivity (dielectric function); Physics; Specific phase transitions; Structure analysis
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2009.03.042

In the present study the thermal analysis, hyperfine structure and electric transport properties were investigated for the (60− X) P 2O 5 (20+ X) V 2O 5 20Fe 2O 3 [PVF] ( X=10, 15, 20, 30 and 40 mol%) glasses. The glassy state of the samples was characterized using DTA and Mössbauer spectroscopy. Two glass transition temperatures T g1 and T g2 were detected at the DTA traces of the investigated system. The glassy sample with X=20 mol% (PVF3) is of the highest glass thermal stability where Δ T=177±2 K. Also, it has the highest value of crystallization activation energy for the first and the second crystallization peaks (305 and 316±3 kJ/mol%) among the other samples. The obtained ME spectra showed the presence of Fe 3+ alone located in the tetrahedral and octahedral sites. Increasing V 2O 5 content, the dc conductivity increases while the activation energy decreases. The room temperature dc conductivity is typically 2.9×10 −7–2.5×10 −5 with an activation energy 0.60–0.37±0.011 eV. The power law exponent s was found to be temperature dependent and exhibited a minimum, for PVF3 and PVF4. The dielectric constant ε 1( ω) increases with increasing V 2O 5 content which was attributed to the increase in the deformation of glass network.