Structure and Microwave Dielectric Properties of Low Firing Bi2Te2W3O16 Ceramics. Issue 4 (26th December 2013)

• Record Type: Journal Article
• Authors: Schileo, Giorgio; Dias, Anderson; Moreira, Roberto L.; Jackson, Tim J.; Smith, Paul A.; Chung, Kelvin T. S.; Feteira, Antonio; Alford, N.
• Is Part Of: Journal of the American Ceramic Society. Volume 97:Issue 4(2014)
• Page Start: 1096
• Page End: 1102
• Publication Date: 2013-12-26
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.12738
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace12738-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Dense Bi<sub>2</sub>Te<sub>2</sub>W<sub>3</sub>O<sub>16</sub> ceramics were prepared by the conventional solid‐state reaction route. X‐ray diffraction data show the room‐temperature (RT) crystal symmetry of Bi<sub>2</sub>Te<sub>2</sub>W<sub>3</sub>O<sub>16</sub> to be well described by the centrosymmetric monoclinic <italic>C</italic>2<italic>/c</italic> space group [<italic>a</italic> = 21.280(5) Å, <italic>b</italic> = 5.5663(16) Å, <italic>c</italic> = 12.831(3) Å and β = 124.014(19)° and <italic>Z</italic> = 4]. Raman spectroscopy analyses are in broad agreement with space group assignment, but also revealed the presence of Bi<sub>2</sub>W<sub>2</sub>O<sub>9</sub> as a secondary phase. This phase is present as plate‐like grains embedded on a fine‐grained equiaxed matrix, as revealed by scanning electron microscopy. From the fitting of infrared reflectivity data the relative permittivity, ε<sub>r</sub>, was estimated as 34.2, and the intrinsic quality factor, <italic>Q</italic><sub>u</sub><italic> × f</italic> as 57 500 GHz. At RT and microwave frequencies, Bi<sub>2</sub>Te<sub>2</sub>W<sub>3</sub>O<sub>16</sub> ceramics sintered at 720°C for 6 h exhibit ε<sub>r</sub> ~ 34.5, <italic>Q</italic><sub>u</sub><italic> × f </italic>=<italic> </italic>3173 GHz (at 7.5 GHz), and temperature coefficient of resonant frequency, τ<sub>f</sub> = −92 ppm/°C. This shows a good agreement between the estimated and measured ε<sub>r</sub> values, but also shows that, in principle, the dielectric losses of the ceramics are of extrinsic origin.</p> </abstract>