Crystallization, dielectric and optical studies on strontium tetraborate glasses containing bismuth titanate

Shankar, MV and Varma, KBR (1998) Crystallization, dielectric and optical studies on strontium tetraborate glasses containing bismuth titanate. In: Materials Research Bulletin, 33 (12). pp. 1769-1782.

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Abstract

Glass nanocomposites comprising nanocrystallites of bismuth titanate, $Bi_4Ti_3O_{12}$ (BiT), dispersed in a glass matrix of strontium tetraborate $SrB_4O_7$ (SBO) were obtained by the controlled crystallization of glasses with the composition $2xBi_2O_3-3xTiO_2-(100 - 5x)SBO, (10 \leq x \leq 15)$. Ultrasonic treatment (UST) of the glass samples with an aqueous suspension of BiT followed by conventional heat treatment (HT) readily yielded the desired crystalline phase, which was otherwise difficult to obtain by conventional heat treatment. The phase formation was confirmed by powder X-ray diffraction (XRD) studies. High-resolution transmission electron microscopy (HRTEM) was used to confirm the crystallinity, and the average size of the crystallites was found to vary from 60 to 70 nm. The dielectric constant $(\varepsilon _r)$ of the glass samples was found to increase with increase in $Bi_2O_3–TiO_2$ content, and the dielectric loss $(tan\delta)$ values were reasonably low (0.02 to 0.04) for all the compositions under study, in the 100 Hz to 100 kHz frequency range. The frequency response of $\varepsilon _r$ and dielectric loss $(tan\delta)$ of the crystallized sample exhibited sharp piezoelectrically induced resonances in the 185 to 200 kHz range. The resonance peaks were found to shift towards lower frequencies with increasing temperature and higher frequencies with increasing pressure. The temperature dependence of the stiffness coefficient (C) was defined, using the resonance data. The refractive index of the glasses and the second harmonic generation (SHG) efficiency of the glass-ceramics were found to increase with increase in $Bi_2O_3–TiO_2$ or crystalline BiT content.

Item Type:	Journal Article
Publication:	Materials Research Bulletin
Publisher:	Elsevier
Additional Information:	Copyright of this article belongs to Elsevier.
Keywords:	Glasses;Chemical synthesis;Electron microscopy;Dielectric properties;Optical properties
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	07 Dec 2006
Last Modified:	19 Sep 2010 04:32
URI:	http://eprints.iisc.ac.in/id/eprint/9017

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