Sol-gel powder synthesis and preparation of ceramics with high- and low-temperature polymorphs of Ba_xSr_1-xZn₂Si₂O₇ (x = 1 and 0.5): A novel approach to obtain zero thermal expansion

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• 作者：Michael Kracker ^{michael.kracker@uni-jena.de" class="auth_mail" title="E-mail the corresponding author} ; Christian Thieme ; ^{christian.thieme@uni-jena.de" class="auth_mail" title="E-mail the corresponding author} ; Johannes Hä ; &szlig ; ler ^{johannes.haessler@uni-jena.de" class="auth_mail" title="E-mail the corresponding author} ; Christian Rü ; ssel ^{ccr@uni-jena.de" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Sol&ndash ; gel ; Ceramics ; Thermal expansion ; Sintering ; Dilatometry
• 刊名：Journal of the European Ceramic Society
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：36
• 期：8
• 页码：2097-2107
• 全文大小：6920 K

文摘

Samples with the stoichiometry BaZn₂Si₂O₇ as well as Ba_0.5Sr_0.5Zn₂Si₂O₇ were prepared using a sol–gel procedure. Hot pressing led to dense and crack free specimens. The BaZn₂Si₂O₇ samples showed a steep increase in volume in the temperature range from 130 to 400 °C attributed to the transition of the low temperature to the high temperature phase. The coefficient of thermal expansion of the Ba_0.5Sr_0.5Zn₂Si₂O₇ sample was close to zero at temperatures up to 130 °C and then approaches a value of 4 × 10⁻⁶ K⁻¹ up to a temperature of 900 °C. Ba_0.5Sr_0.5Zn₂Si₂O₇ powders prepared by conventional solid state reactions could not be fully densified by the supplied hot pressing procedure. Their thermal expansion was strongly negative and showed a strong hysteresis. This is the first report on dense sintered ceramics based on the SrO/BaO/ZnO/SiO₂ system with thermal expansion close to zero.