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Design of LTCC with High Thermal Expansion
Author(s) -
Eberstein Markus,
Glitzky Carsten,
Gemeinert Marion,
Rabe Torsten,
Schiller Wolfgang A.,
Modes Christina
Publication year - 2009
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/j.1744-7402.2008.02316.x
Subject(s) - thermal expansion , materials science , devitrification , composite material , sintering , ceramic , dilatometer , microstructure , phase (matter) , frit , borosilicate glass , permittivity , crystallization , dielectric , chemical engineering , chemistry , organic chemistry , engineering , optoelectronics
New applications of low‐temperature co‐fired ceramics (LTCC), such as pressure sensors or integrated functional layers, require materials that possess higher coefficients of thermal expansion (CTE). To fabricate LTCC with elevated CTE, two methods of material design are examined: firstly, glass ceramic composites (GCC), which consist of >50 vol% glass in the starting powder, and, secondly, glass‐bonded ceramics (GBC), where glass is added as a sintering aid only. The CTE of GBC is mainly determined by the crystalline component. For GCC, the CTE can be well predicted, if CTE and elastic data of each phase in the microstructure are known. A nonlinear characteristic of the CTE versus phase composition was found with increasing E crystals / E glass ratio and absolute CTE difference between the components. The glass composition and glass amount can be used to compensate the fixed properties of a crystalline material in a desired way. However, because the CTE and permittivity of a glass cannot be chosen independently, an optimum glass composition has to be found. For a given LTCC, it is possible to control the devitrification by shifting the glass composition. In this way, the resulting CTE values can be predicted more exactly and tailoring becomes possible. Different LTCC materials, based on the crystalline compounds Ba(La,Nd) 2 Ti 4 O 12 , ZrO 2 (Y‐TZP), SiO 2 (quartz), and specially developed glasses, possessing an elevated CTE of around 10 × 10 −6 K −1 while showing permittivity ɛ r between 6 and 63, are introduced.