Abstract
The structural and physical properties ofxFe2O3-(40-x)B2O3-60V2O5 (0≤x≤20)glass system have been investigated. The samples were prepared by normal melt-quench technique. The structural changes were inferred by means of FTIR by monitoring the infrared (IR) spectra in the spectral range 600–4000cm-1. The absence of boroxol ring (806 cm-1) in the present glass system suggested that these glasses consist of randomly connectedBO3andBO4units. The conversion ofBO3toBO4andVO5toVO4tetrahedra along with the formation of non-bridging oxygen's (NBOs) attached to boron and vanadium takes place in the glasses under investigation. The density and molar volume of the present glass system were found to depend onFe2O3content. DC conductivity of the glass system has been determined in the temperature range 310–500 K. It was found that the general behavior of electrical conductivity was similar for all glass compositions and found to increase with increasing iron content. The parameters such as activation energy, average separation between transition metal ions (TMIs), polaron radius, and so forth have been calculated in adiabatic region and are found consistent with Mott's model of phonon-assisted polaronic hopping.
Highlights
Borate glasses are generally insulating in nature, and the addition of transition metal oxide such as Fe2O3 and V2O5makes these glasses semiconducting [1, 2]
It has been reported that addition of a network modifier in borate glasses could produce the conversion of the triangular BO3 structural units to BO4 tetrahedra with coordination number of 4, which are incorporated in more complex cyclic groups such as diborate, triborate, tetra or pentaborate, and the formation of non-bridging oxygen (NBOs) atoms [8, 9]
Similar results have been reported for V2O5-B2O3 glasses [22, 23]
Summary
Borate glasses are generally insulating in nature, and the addition of transition metal oxide such as Fe2O3 and V2O5makes these glasses semiconducting [1, 2]. These semiconducting glasses have been extensively studied owing to their potential applications as optical and electrical memory switchings, cathode materials for making solid state devices, and optical fiber [3,4,5]. The electron-phonon interaction in these glasses is strong enough to form small polaron, and the electrical conduction process occurs by the hopping of small polarons between different valence states as proposed by Austin and Mott [2] Hoping conduction in these glasses was generally known to be adiabatic for V2O5 content. The objective of present paper is to study the structural and physical properties of iron-boro-vandate glasses to shed some light on the role of the Fe2O3 in this glass system
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