Materials Chemistry and Physics 88 (2004) 138–144 AC conductivity studies of lithium borosilicate glasses: synthesized by sol–gel process with various concentrations of nitric acid as a catalyst P. Muralidharan, M. Venkateswarlu 1 , N. Satyanarayana ∗ RamanSchoolofPhysics,PondicherryUniversity,Pondicherry605014,India Received 10 March 2004; accepted 28 June 2004 Abstract Glasses of lithium borosilicate (LBS) were synthesized by sol–gel process with various concentrations (x = 0.01, 0.1, 1.0, 2.5 and 5 N) of nitric acid as a catalyst. LBS samples glass forming temperatures were monitor and optimized through XRD studies at different stages from gel to glass and to multicrystalline phases. XRD, FTIR and DSC techniques were used in the characterization of the LBS samples. Impedance measurements were made on LBS glasses, heat-treated at 698 K, synthesized with various concentrations of nitric acid at different temperatures and data were analyzed using Boukamp equivalent circuit software. The bulk conductivity was calculated from the analysis of impedance data and it is found that LBS glass synthesized with 2.5 N nitric acid concentration showed high conductivity σ = 1.45 (±0.02) × 10 -7 S cm -1 at 443 K. The activation energy (E a ) was obtained from the slopes of log(σT) versus 1000/T plot in the region of 443–613 K and it is found to be 0.51 ± 0.03 eV for high conducting (x = 2.5 N) LBS glass. The conductivity variations with LBS glasses synthesized with various concentrations of nitric acid as a catalyst is explained based on conductivity expression. AC conductivity were calculated from impedance data and analyzed using Jonscher’s power law (JPL) exponent (s) for LBS glasses synthesized under various concentrations of nitric acid. The power law exponent s is found to be non-linear with the concentrations of nitric acid used in the synthesis of LBS glasses. © 2004 Published by Elsevier B.V. Keywords: LBS glasses; Sol–gel process; Concentration of acid; Impedance; AC conductivity 1. Introduction High ion conducting solids are being investigated in wide range as an important component in the fabrication of newer and improved solid state ionic device [1,2]. These high ion conducting solids are synthesized as different single/polycrystalline as well as amorphous/glasses forms like bulk, powder, sheet, thin films, fibers, etc. Augmentation in ionic conductivity of the samples is achieved by varying formers compositions or modifier to former ratios and also by various synthesis processes like melt quench, thermal evaporation, sol–gel process, etc. [1,2]. In particular, sol–gel ∗ Corresponding author. Tel.: +91-413-2655991-99x404; fax: +91-413-2655265/2655211. E-mailaddress: nallanis2000@yahoo.com (N. Satyanarayana). 1 Present address: Department of Chemical Engineering, NTUST, Taipei, Taiwan. process has attracted the attention of the electrochemical community as a resourceful way for the research of modified electrodes and solid electrolytes [3]. Hence, tailor made compounds are synthesized through sol–gel process under high controlled reaction, required design and structure of materials, relatively at low temperatures [3–7]. Materials of better property are synthesized through sol–gel process by varying not only constituent but also parameters like solvent, water, catalysts, temperature, etc., of the reaction [5]. Catalysts play vital roles in determining the hydrolysis and polycondensation reaction rates and thus, result in struc- tural modification of the matrix. Mineral acids and ammonia are most generally used catalyst in the sol–gel process [5]. Acid catalyst promotes hydrolysis reaction in the process through an electrophilic attack, according to the following reaction, (RO) 3 SiOR + H 3 O + → (RO) 3 SiOH + H + + HOR (1) 0254-0584/$ – see front matter © 2004 Published by Elsevier B.V. doi:10.1016/j.matchemphys.2004.06.032