építôanyag § Journal of Silicate Based and Composite Materials Ceramic radiotransparent materials on the basis of BaO-Al 2 O 3 -SiO 2 and SrO-Al 2 O 3 -SiO 2 systems georgiy v. LISACHUK § Lisachuk@kpi.kharkov.ua ruSlan v. KRYVOBOK § National Technical University “Kharkiv Polytechnic Institute” § krivobok_ruslan@ukr.net elena y. FEDORENKO arteM v. ZAKHAROV Érkezett: 2015. 02. 06. § Received: 06. 02. 2015. § http://dx.doi.org/10.14382/epitoanyag-jsbcm.2015.4 Abstract Based on the literature review, the authors made a justified choice of ceramic materials with a low dielectric constant and dielectric loss tangent. The composition and process parameters (burning temperature - 1550 °C, burning duration - 5 hours) of producing of celsian and Sr-anorthite ceramics with low dielectric properties were defined. The phase composition of products of burning was examined. X-ray phase studies of Sr-ceramics after burning were conducted. Keywords: Ceramic radiotransparent materials, celsian, Sr-anorthite, dielectric constant, reflection coefficient of radio waves Prof. Georgiy V. LISACHUK Doctor of Sciences (since 2003), full Professor (since 2007). Winner of the State Prize of Ukraine in Science and Technology (2006). Honoured master of sciences and engineering (2009). Specialist in material sciences of resource saving and energy-saving technologies, new structural ceramic materials and coatings. Author and co- author of more than 250 papers, 3 monographs, 83 author’s certificates and patents. Leads the training of Postgraduates, Masters and Bachelors in advanced material sciences. 7 candidate’s dissertations of postgraduates have been defended under his guidance. Head of Research department of NTU “KhPI”. Lecturer of major courses at the Department of Technology of ceramics, refractories, glass and enamels. Ruslan V. KRYVOBOK Candidate of Technical Sciences (since 2007), Senior researcher (since 2010). Winner of the Prize of the President of Ukraine for young scientists (2010). Honoured master of sciences and engineering (2009). Specialist in material sciences of new special-purpose ceramic materials and coatings. Author and co-author of more than 24 papers, 6 patents. Deputy Head of Scientific and Research Part NTU “KhPI”, Elena Y. FEDORENKO Doctor of Sciences (since 2013), full Professor (since 2014). Author and co-author of more than 125 papers, 2 monographs, 25 author’s certificates and patents. Artem V. ZAKHAROV Graduate student. Author and co-author of more than 5 papers, 2 author’s certificates and patents. 1. Introduction Ceramic radiotransparent materials are non-metallic materials which do not substantially alter the amplitude and phase of the electromagnetic wave of radio-frequency range passing through them. Radiotransparency of ceramic materials is provided by low dielectric losses in the range of operating temperatures (tgδ = 10 -2 …10 -5 , ε<10) and by low value of refection coefcient of radio waves (S). Ceramic radiotransparent materials are mainly used for the manufacture of radomes protecting antennas against the environmental infuences. Besides the above mentioned requirements radio-ceramic materials must have: a high value of thermal resistance, low coefcient of linear thermal expansion and at the same time should protect the equipment from external infuences [1-8]. Nowadays a large number of materials in the world practice are used as radiotransparent silicate materials. Classifcation of radiotransparent silicate materials is shown in Fig. 1. Te main disadvantages of radiotransparent materials based on the vitroceramics and glass materials are their brittleness and the disadvantage of composite materials is their high manufacturing cost. At the moment ceramic materials based on quartz, high- alumina and mullite ceramics, silicon nitride, boron and others are widely used for the production of radiotransparent materials. Table 1 shows the most important advantages and disadvantages of the main ceramic radiotransparent materials. Fig. 1 Classifcation of radio-silicate materials 1. ábra Rádió-szilikát anyagok csoportosítása 20 | építôanyag § JSBCM § 2015/1 § Vol. 67, No. 1 Name of material Advantages Disadvantages Quartz ceramics High thermal stability, stability of dielectric properties over a wide temperature range High melting temperature, low mechanical strength, the upper limit of operating temperature is 1000 °C High-alumina ceramics High mechanical properties, resistance to corrosion High temperature of sintering, low resistance to thermal shock – not higher than 200 °C Ceramics based on silicon nitride High strength characteristics at high temperatures (1500 °C), good resistance to oxidation and thermal stresses High sintering temperature, complex technological process of production Ceramics based on boron nitride Has the best dielectric properties at temperatures up to 2000 °C Table 1 Radiotransparent ceramic materials 1. táblázat Rádiótranszparens kerámia anyagok