Thermal, structural, optical, and dielectric properties of (100 -x)Li 2B 4O 7 - X(BaO-Bi 2O 3-Nb 2O 5) glasses and glass-nanocrystal composites

C. Karthik, K. B.R. Varma

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2 Scopus citations

Abstract

Transparent glasses in the system (100 - x)Li 2B 4O 7 - x(BaO-Bi 2O 3-Nb 2O 5) (x = 10, 20, and 30) were fabricated via the conventional melt-quenching technique. The amorphous and glassy characteristics of the as-quenched samples were established by the differential thermal analyses (DTA) and X-ray powder diffraction (XRD) studies. Glass-nanocrystal composites (GNCs) i.e., the glasses embedded with BaBi 2Nb 2O 9 (BBN) nanocrystals (10-50 nm) were produced by heat-treating the as-quenched glasses at temperatures higher than 500°C Perovskite BBN phase formation through an intermediate fluorite-like phase in the glass matrix was confirmed via XRD and transmission electron microscopic (TEM) studies. The optical transmission properties of these GNCs were found to have a strong compositional (BBN content) dependence. The refractive index (n = 1.90) and optical polarizability (α o. = 15.3 × 10 -24 cm 3) of the GNC (x = 30) were larger than those of as-quenched glasses. The temperature dependent dielectric constant (Er) and loss factor (D) for the glasses and GNCs were determined in the 100-40 MHz frequency range. The Er was found to increase with increase in heat-treatment temperatures, while the loss of the glass-nanocomposites was less than that of as-quenched glasses. The sample heat-treated at 620°C/1 h (x = 30) exhibited relaxor behavior associated with a dielectric anomaly in the 150-250°C temperature range. The frequency dependence of the dielectric maximum temperature was found to obey the Vogel-Fulcher relation (E a = 0.32 eV and T f = 201 K).

Original languageEnglish
Pages (from-to)1006-1013
Number of pages8
JournalJournal of Nanoscience and Nanotechnology
Volume7
Issue number3
DOIs
StatePublished - Mar 2007
Externally publishedYes

Keywords

  • Dielectric properties
  • Glass-ceramics
  • Layered perovskites

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