Berlin 2015 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 16: Focused Session on GHz Dielectrics: Materials for Mobile Communication I (DF with HL/MM)

DF 16.6: Talk

Thursday, March 19, 2015, 11:50–12:10, EB 407

Ba₄Al₂Ti₁₀O₂₇ glass-ceramics as dielectric materials for antenna elements in wireless communications — •Martun Hovhannisyan¹, Hubertus Brauna¹, Yuliang Zheng², Arshad Mehmood², Martin Letz¹, and Rolf Jakoby² — ¹Material & Technology Development, SCHOTT AG, Hattenbergstrasse 10, Mainz, 55122, Germany — ²Technical University of Darmstadt, Darmstadt, D-64283 Darmstadt, Germany

Dielectric glass-ceramics with Ba₄Al₂Ti₁₀O₂₇ as the main crystalline phase are obtained by controlled heat-treatment of a non-porous bulk-glass phase. Such a non-porous material has advantages over ceramics with residual porosity wherever metallization steps are applied to the material. Depending on the details of heat-treatment profile the Ba₄Al₂Ti₁₀O₂₇ is formed as a main phase with secondary phases BaTi₄O₉ or BaAl₂Si₂O₈. Microstructural observation using scanning electron microscopy (SEM) shows nanometer-sized crystals (40nm) grown in a true glass phase. The microwave dielectric characterization using Hakki-Coleman setup shows a Qf from 2000 GHz to 10.000 GHz, dielectric constant from 19 to 33 and |tf| of <20 ppm/K. Balancing between different crystalline phases allows to adjust |tf| to zero. To our knowledge the present work is the first one emphasizing the attractiveness of the microwave dielectric properties of the phase Ba₄Ti₁₀Al₂O₂₇. Such glass-ceramics are well suited for antenna and filter applications in microwave electronics.