Prof. Christian Rüssel – Always One Step Ahead and in Search of Something New in Glass Science

Journal of ChemicalRuzha Technology Harizanova, and Metallurgy, Ivailo Gugov 50, 4, 2015, 345-356

PROF. CHRISTIAN RÜSSEL – ALWAYS ONE STEP AHEAD AND IN SEARCH OF SOMETHING NEW IN GLASS SCIENCE

Ruzha Harizanova, Ivailo Gugov

Department of Physics, Received 19 January 2015 University of Chemical Technology and Metallurgy, Accepted 20 May 2015 8 Kl. Ohridski, 1756 Sofia, Bulgaria E-mail: [email protected]

ABSTRACT

The 18th Conference on Glass and Ceramics is dedicated to Prof. Christian Rüssel for his outstanding contributions to glass science and technology. Due to his close connections to Bulgarian scientists from Bulgarian Academy of Sciences and University of Chemical Technology and Metallurgy he was awarded the title Dr. h. c. of the University of Chemical Technology and Metallurgy on September 29th, 2014, while on October 7th, 2014 he received the Golden Band Honorary Medal “Prof. Marin Drinov” from the Bulgarian Academy of Sciences. Christian Rüssel was born on the 1st of August, 1952 in Nürnberg. He obtained his diploma in Chemistry in 1980. He is married to his wife Angela, who is also an engineer in glass and ceramics. He has a daughter Kathrin and two grandchildren, Clara and Johann. Between 1980 and 1992 C. Rüssel gathered tremendous scientific experience by successively joining the Institute of Physical and Theoretical Chemistry, Erlangen University, the Fraunhofer Institute of Solar Energy, Freiburg and the Faculty of Engineering, Department of Materials Science, Erlangen. In 1992, he headed the Otto-Schott-Institut for Glass Chemistry, Jena where he organized four Otto Schott Colloquia. He was an active member of the management of the Friedrich Schiller University working as Dean of the Faculty of Chemistry and Geoscience (1996-1997) and Vice Rector of Research (2002-2004). His versatile investigations encompass novel and intriguing topics: electrochemistry of polyvalent metal ions in glass melts; energy storage; oriented glass-ceramics by extrusion or electrochemically induced nucleation; nano-sized glass ceramics and self-constraint crystallization; electron backscatter diffraction studies of surface crystallization of glass; high temperature spectroscopy of redox pairs in glass; synthesis of nanocrystalline glass ceramics of advanced thermo- mechanical and optical properties. Keywords: glass science, electrochemistry of metals, self-constraint crystallization, nanocrystalline glass ceramics.

INTRODUCTION be paid to his carrier prior to and after arriving at Jena University and to his achievements in the field of the Prof. Christian Rüssel is to everybody who knows synthesis and study of numerous oxide and non-oxide him, even to those who have just a vague idea of his materials with advanced applications. His work and activities, a vigorous person and a scientist with sound personal life will be illustrated by numerous photographs judgement and profound knowledge of practically all and supported by materials from the Otto Schott Insti- topics of chemistry and physical chemistry of inorganic tute for Materials Research archives, provided with the materials. This paper will briefly review Christian Rüs- courtesy of his colleagues and co-workers, and from his sel’s personal and scientific life. Main attention will personal collection.

345 Journal of Chemical Technology and Metallurgy, 50, 4, 2015

EARLY LIFE AND FAMILY He left Erlangen University and joined the Fraun- hofer Society. He started working at the newly funded Christian Rüssel was born on the 1st of August, 1952 Fraunhofer Institute of Solar Energy in Freiburg. His in Nürnberg, Southern Germany as the younger son of an interests were in the field of energy storage, especially actor at the Nürnberg Theater, who later had a bookshop in electrochemical systems. He constructed fuel cells in Nürnberg (Fig. 1). His mother was an opera singer and redox batteries, especially those based on iron and until she retired 30 years later. He has a three years older chromium [1]. brother who succeeded his father’s bookshop. During this period of time he started working with industrial partners and the experience obtained was of tremendous importance for his future activity and suc- cess as a scientist and an administrator in Jena. After 15 months he left the Fraunhofer Society and went back to Erlangen University joining the Depart- ment of Glass and Ceramics of the Institute of Materials Science at the Faculty of Engineering. Shortly before that Prof. Helmut Schaeffer left the Institute to become the managing director of the Ger- man Glass Society and some of his projects remained unfinished. They were mainly focused on electrochemistry in glass melts, on zirconia sensors of oxygen activity and Fig. 1. Christian Rüssel in 1954. corrosion of metal electrodes in molten glass. Christian Rüssel grew up in Nürnberg, where he The new task faced by Christian Rüssel was to went to school from 1958 to 1971. Then he joined the combine his expertise in electrochemistry with the army and did an alternative civilian service until 1974. knowledge on glass and ceramics widely available at He started to study Chemistry and got his Diploma in the Institute of Materials Science in Erlangen. He suc- 1980. In between, he travelled a lot in oriental countries. ceeded in performing electrochemical measurements Nowadays, Christian Rüssel is married to his wife in glass melts applying square-wave voltammetry to Angela who is also an engineer in the field of glass and determine the diffusion coefficients of polyvalent ions ceramics. They have a daughter Kathrin, a granddaughter [3] in these media. Clara and a grandson Johann. In his leisure time Prof. Later, the method was also used for the quantitative Rüssel is collecting old furniture and carpets. If he has determination of their concentrations, even in case of some extra time, he rides his bicycle. the simultaneous presence of numerous polyvalent ions [4]. At this time, he also recorded the first stationary EDUCATION, CARRIER AND PROFESSIONAL current-potential curves referring to the corrosion of EXPERIENCE PRIOR TO JENA molybdenum electrodes in glass melts [5]. He also performed some work on ceramics, focus- In 1980, Christian Rüssel joined the Institute of ing predominantly on non-oxides chemical synthesis. Physical and Theoretical Chemistry at Erlangen Univer- During his work at the Institute of Materials Science sity where he performed some work in electrochemistry; in Erlangen he developed the only (nearly) universal he studied the kinetics of electron transfer. polymeric route for the synthesis of nitrides [6] and Prof. Walther Jaenicke was his advisor. It is worth fluorides [7]. Later he applied these routes to prepare noting that Christian Rüssel used Marcus theory to in- oxynitride [8] and fluoride glasses [9]. terpret his results. This happened some ten years before In 1991 he wrote and defended his second disserta- Marcus obtained his Nobel Prize and his theory was tion (Dr.-Ing. habil.) on the redox chemistry of glasses not widely known. He finished his PhD (Doctor rerum and glass melts and was appointed as Docent in Glass naturalium) in the spring of 1984. and Ceramics (Fig. 2). 346 Ruzha Harizanova, Ivailo Gugov

Fig. 2. Prof. Christian Rüssel – habilitation ceremony.

MOVING TO JENA TO INHERIT THE TRADI- TION OF SCHOTT, ABBE AND ZEISS

In 1992 he was offered to head the Otto Schott Institute for Glass Chemistry at the Friedrich-Schiller- University Jena. He succeeded the famous glass scientist Werner Vogel, the Founder and Director of the Otto- Schott-Institut, who retired in 1990 (Fig. 3). Christian Rüssel was the first natural scientist appointed to Jena University after the German Unification. By the way, the advisor of Christian Rüssel’s Ph.D. thesis Walther Jaenicke was in Jena in 1948, while Werner Vogel was one of his students. Coming to the Otto-Schott-Institut, Prof. Rüssel inherited the institute’s tradition to work in the spirit of Otto Schott, Ernst Abbé and Carl Zeiss (Fig. 4), i.e. to carry out a team work with the participation

Fig. 3. Prof. Werner Vogel and Prof. Rüssel at the days of Fig. 4. Otto Schott, Ernst Abbe and Karl Zeiss – inspiration the Otto-Schott-Institut in 2008. for cooperation among chemistry, technology and physics.

347 Journal of Chemical Technology and Metallurgy, 50, 4, 2015 of chemists, physicists, glass-technologists and indus- was the first homogeneous chemical reaction whose try. At that time Schott Glassworks in Jena, the main kinetics could directly be measured in a glass melt. cooperation partner of the Otto Schott Institute, was Surprisingly, its activation energy strongly depended on acquired by Schott Mainz, and hence lost its autonomy. the type of the polyvalent ion present. Christian Rüssel Christian Rüssel had to find new research partners and explained this fact, on the ground of the Marcus theory, to look for new financial sources as the contribution of with the reorganization energies, which were especially the University was continuously decreasing. This af- high in case of the coordination numbers’ change in the fected mainly the number of the employees supported course of the reaction [13]. This just closed the loop by the University and the funds required for the provi- bringing him back to his earliest contact with science. sion of state-of-the-art equipment. Nevertheless, due to Oriented crystallization from glass melts and the his effective network of industrial partners Prof. Rüssel EBSD method managed to find resources through public and private The preparation of oriented glass-ceramics was a projects to keep a high level team. new subject in the early 90s not only for the Otto Scott Institute. There the work was initially focused on extru- SCIENTIFIC ACTIVITY IN JENA sion of partially crystalline melts and the development of a completely new method, namely, the electrochemically In Jena Christian Rüssel continued his older sci- induced nucleation [14]. The latter referred to the follow- entific activities but started also to work on numerous ing: a platinum wire was inserted in a glass melt placed in new subjects in the field of glasses and glass-ceramics: a platinum crucible and a potential was applied between electrochemistry in melts; redox-reactions in melts; the crucible and the wire acting as a cathode. There the high-temperature spectroscopy; oriented crystallization melt was reduced, e.g. Ti4+ was reduced to Ti3+, which in glass melts; nanocrystallization in glass; synthesis of led to viscosity decrease. This resulted in nucleation nanocrystalline powders using polymeric routes; materi- near the cathode and subsequent crystal growth (Fig. 5). als for the photonics; preparation of glass-ceramics of The first structures obtained by this method were highly special applications from glass. oriented. In fact such an extent of orientation was not Electrochemistry and redox-reactions in melts achieved [15] by any other method applied so far for Glass melts thermodynamics was studied. This in- unidirectional crystallization in a glass melt (Fig. 6). cluded recording of stationary current-potential curves Highly oriented structures were obtained by ex- referring to the corrosion of metals in contact with melts, trusion as well. Here the papers on lithium disilicate, especially in case of molybdenum electrodes [5]. The phlogopite and apatite are to be mentioned [16 - 19]. diffusion coefficients of numerous metal ions in glass The work in this field was additionally complemented melts, including polyvalent metals, were determined. by studies on the crystallization of oxynitride glasses 3d-contact points mode impedance spectroscopy was [20] and ferroelectric phases from glass [21]. successfully performed in glass melts. Adsorption The surface crystallization of glass was also a topic of processes at high temperatures (T > 1000°C) were investigated [10]. High-temperature spectroscopy The redox chemistry work was continued until recently and was complemented by high temperature spectroscopic measurements [11]. The focus was on performing redox-reactions with simultaneous temperature change. These reactions were frozen below a certain temperature value depending on the cooling rate. Changing the temperature and monitoring the changes in the spectra as a function of time enabled to prove that the “redox-relaxation” observed was the third relaxation Fig. 5. Electrochemically induced crystallization of fres- process in glasses [12]. It should be underlined that this noite in glass. 348 Ruzha Harizanova, Ivailo Gugov

verified by the work carried out within the framework of the project INTERCONY funded by the European Com- munity. Spanish and Greek scientists as well as members of the Bulgarian Academy of Sciences took also part in this project using high resolution transmission electron microscope [27] as well as anomalous small angle x- ray scattering [28]. Theoretical considerations were elaborated by Prof. Isak Avramov from the Institute of Physical Chemistry of the Bulgarian Academy of Sci- ence. It is possible to prepare glass-ceramics containing Fig. 6. EBSD pattern of dendrite of fresnoite cut parallel to a crystalline phase of 10 % if these results are properly the c-axis; main orientation is marked orange. used. They will be fully transparent for visible light and increasing importance in the past few years. A new method, can be used as optical materials [26, 27]. electron backscatter diffraction (EBSD), was available Synthesis of nanocrystalline powders using poly- at the Otto-Schott-Institut. It provided to identify certain meric routes crystal phases and to determine the orientation of a crystal A nearly universal method for the preparation of at the sample surface [22, 23] inside a scanning electron metal nitrides, carbides [6] and fluorides [7] was pro- microscope. Thus an overall idea of the texture of the posed for the first time. It was later used for the prepara- surface and of every individual crystal could be obtained. tion of oxynitride [8] and fluoride glasses [9]. Besides, Surprisingly, it was found that the crystals at the immedi- a nearly universal precursor route for fluorides was also ate surface of the glass have already orientations. In most developed. It was used to synthesize fluoroapatite [29] cases they change if the crystals grow further in the bulk. as well as nitride and fluoride coatings [30]. Nanocrystallization in glass Preparation of glass-ceramics of special applica- An important topic in the past few years was the tions starting from glass preparation of nano glass ceramics. This work was Another important field of investigation is the initially focused on the crystallization of fluorides from preparation of glass-ceramics of special applications silicate glasses [24, 25]. During the course of this pro- using glass as a starting material with the application of cess the viscosity of the melt increases. This leads to the appropriate time-temperature regimes. Different types of formation of a highly viscous layer around the growing glass-ceramics were prepared during Prof. Rüssel’s years crystals. This layer is enriched in SiO2 and depleted in in Jena: glass-ceramics of special mechanical properties those components which if added to a melt decrease the [31], glass-ceramics for dentistry [32] (Fig. 8); glass- viscosity, for example fluoride and alkaline earth cations are depleted near the crystal (Fig.7). This leads to the diffusion coefficient decrease and hence to a decrease in the crystal growth velocity [26]. These assumptions were

Fig. 8. TEM-micrograph of a glass-ceramic sample an- Fig. 7. Model of self-constraint crystallization in glass-ceramics. nealed at 950 °C for 3 h for application in the dentistry.

349 Journal of Chemical Technology and Metallurgy, 50, 4, 2015

Fig. 9. SEM-micrographs of freshly sputtered and annealed gold layers. ceramics for hard discs [33], sintered glass-ceramics, crystallizing sealing glasses [34]. Functional metal layers coatings on glass A new topic for the Otto-Schott-Institut was developed in the last years. It referred to the formation [35] of functional metal coatings on glass (Figs. 9 and 10). Metal layers of thickness of 5 nm to 30 nm were thermally treated which resulted in a dewetting of the metal layer and the formation of metal islands of diameters in the range from 30 nm to 300 nm. These layers can be used as decorative coatings (e.g. gold ruby layers) or for various sensor applications. Materials for the photonics Fig. 10. SEM-micrograph of the annealed surface super- An increasing amount of work was also done in the imposed by a frame indicating where an EBSD-scan was field of optical materials. It was attempted to dope the performed. nano-crystals formed in glass-ceramics with rare earth elements. This was a tool to obtain fluorescent materials lifetimes nearly as good as those of fluoride phosphate for fluorescence [36] or up-conversion [37]. Glasses of glasses (Fig. 11). The growth of polycrystalline ZnS and good thermo mechanical properties were required in the texturing phenomena occurring in it were studied by this case in contrast to the active laser glasses for high EBSD aiming an application [40] as a material for infra- power applications [38] where the starting glasses had red optics (Fig. 12). Glass ceramic materials converting to possess good optical properties. A specific attention the blue light of LEDs into white light were also devel- was paid to the small coefficient of thermal expansion. oped. These materials have much higher temperature It was possible to prepare aluminosilicate glasses [39] resistance and heat conductivity than the conventional of excellent mechanical properties and fluorescence polymer matrix composites [41].

350 Ruzha Harizanova, Ivailo Gugov

of Chemistry and Geoscience. From 2002 to 2004 he was busy as Vice Rector of Research of the Friedrich Schiller University. Some of the managing positions Christian Rüssel has had or is still occupying are: a member of the Referee Board for Graduate Schools of the German Science Foundation (2008-2013), Chairman of TC 22 of the International Commission on Glass (1992-2001), Chairman of the Committee “Forum on Glass” of the German Glass Society (2000-2004), Elected Referee (Materials Science) of the German Science Foundation (2001-2008), Chairman of the Committee “Physics and Chemistry of Glasses” of the German Glass Society - Fig. 11. Fluorescence decay curves of the 4G energy 5/2 since 2004, a board member of the German Society of 3+ level of Sm . Glass Technology – since 2003. For his active part in the scientific world of glass research and for his steady and systematic work on bridging the fundamental science and industry, Christian Rüssel was awarded in 1990 the Industry Award of the German Glass Society.

OTTO-SCHOTT-COLLOQUIA AND INTERNA- TIONAL COLLABORATIONS The numerous international collaborations of Prof. Christain Rüssel have to be mentioned since some of his achievements are due to the team work and the ex- changed ideas with representatives of different scientific schools all over the world. In the years at the Otto- Schott-Institut he worked closely with scientists from Spain (Instituto de Ceramica y Vidro, Madrid), Brazil Fig. 12. SEM-micrograph of a ZnS sample cut perpendicu- (Universidade Federal de Sao Carlos), Greece (Aristotle lar to the growth direction superimposed by the combined University, Thessanoliki) and Bulgaria (Bulgarian Acad- IPF+IQ-map of an EBSD-scan. Pole figures describe the emy of Sciences and University of Chemical Technology <001>-textures observed in the areas 1 and 2. Unit cells and Metallurgy) which resulted in a number of papers but illustrate the preferred orientation while red arrows indicate also in many scientific and educational projects (Figs. 13 the free rotation around a <001>-direction. - 15). Through joint scientific and teaching activities and intensive exchange of students and scientists Prof. Rüs- TEACHING AND MANAGEMENT ACTIVITY sel established contacts with many universities abroad AT THE FRIEDRICH SCHILLER UNIVERSITY (Fig. 16). The Technical University Trencin (Slovakia), The intensive scientific activity of Christian Rüs- the Al-Azhar University (Assiut) and the National Re- sel in Jena has been and is accompanied by his active search Center (Dokki, Giza, Egypt), the Department participation in the management body of the Friedrich of Physics of the Chiang Mai University (Thailand), Schiller University, as well as in the board of directors of the East China University of Science and Technology many other professional and educational organisations. (Shanghai, China), the Queen Mary College (London, Lecturing was another key activity. The courses read by UK), the Physics Department of the Khalid University Prof. Christian Rüssel are: Glass and Glass Technology, (Abha, Saudi Arabia), the Department of Geology of Ceramics and Other Inorganic Non-Metallic Materials, the University of Toronto (Canada), the Institute Laue- Recycling and Materials Characterization. Langevin (Grenoble, France), the Laboratoire Radio From 1996 to 1997 he worked as Dean of the Faculty Analyses et Environnement and Faculté des Sciences de 351 Journal of Chemical Technology and Metallurgy, 50, 4, 2015

Fig. 15. Prof. Ivan Gutzow delivering a lecture at the 8th Fig. 13. Meeting of the DAAD project partners and students Otto-Schott-Colloquium, 2006. at Prof. Rüssel´s house, 2002 – from left to right first row: Prof. Edgar Zanotto, Juliana Meireles-Rocca, Erico Rocca; second row: Ruzha Harizanova, Anna-Candida Martinez- Rodriges, Dr. Günter Völksch, Ralitsa Garkova-Rosenow, Prof. Christian Rüssel, Angela Rüssel, Prof. Yanko Dimit- riev, Dr. Ralf Keding.

Fig. 16. Prof. Rüssel with international trainee-students at the traditional excursion day of the Otto-Schott-Institut, 2004.

Fig. 14. Prof. Vladimir Fokin with Prof. Christian Rüssel and Dr. Ralf Keding. Sfax of the Université de Sfax (Tunisia) are also among his scientific contacts. A special event took place for the first time in 1978. This was the Otto Scott Colloquium. It was organized for four times prior to the time when Christian Rüssel started his work in Jena. It enhanced greatly the international reputation of the institute (Figs. 17) being almost the only opportunity for the glass scientists from the east and the west to meet during the times of separation. Another four Otto Schott Colloquia were later organized. The last one took place in 2006 attracting more than 250 participants. About 50 % of them came from the eastern Fig. 17. Prof. Rüssel at the opening ceremony of the 8th European countries. Otto Scott Colloquium in 2006. 352 Ruzha Harizanova, Ivailo Gugov

CONNECTION TO BULGARIA

Dr. Radost Pascova from the Institute of Physical Chemistry of the Bulgarian Academy of Sciences joined the group of Christian Rüssel in Erlangen. His contacts with Bulgarian colleagues continued in Jena where the cooperation with Bulgaria was already functioning mainly on the ground of the friendship of Prof Werner Vogel with Prof. Ivan Gutzow. Numerous scientists from Bulgaria worked part time at the Otto-Schott-Institut Fig. 19. With the Rector and the Vice rectors after the ever since 1994. Prof. Ivan Gutzow, Prof. Isak Avra- ceremony for awarding Prof. Rüssel the title Dr. h. c. of mov, Dr. Radost Pascova and Dr. Ivailo Gugov were the University of Chemical Technology and Metallurgy, among them. Ralitza Garkova (Rosenow) and Ruzha from left to right: Prof. Eduard Klein (Vice Rector for Harizanova got their PhDs in Jena under the supervi- Science), Prof. Christian Rüssel, Prof. Mitko Georgiev sion of Christian Rüssel. Many students from Sofia had (Rector) and Prof. Senya Terzieva (Vice Rector for Ac- traineeships or worked summer projects in Jena. creditation and Quality). On the 29th of September 2014 Prof. Rüssel was awarded the title “Doctor Honoris Causa” of the Univer- sity of Chemical Technology and Metallurgy (Figs. 18 and 19) for his outstanding contribution to the Bulgarian higher education and the developing of the Bulgarian- German scientific and educational cooperation. On 7th of October 2014 he was awarded the Golden Band Honor- ary medal “Prof. Marin Drinov” – the highest award of

Fig. 20. At the office of the President of the Bulgarian Academy of Sciences, Acad. S. Vodenicharov – ceremony for awarding Prof. Rüssel the Honorary medal `Prof. Marin Drinov`on a golden band of the Bulgarian Academy of Sciences, October 7th, 2014.

the Bulgarian Academy of Sciences for his long term cooperation and joint scientific work with colleagues from the Institute of Physical Chemistry (Fig. 20).

CONCLUSIONS

Christian Rüssel’s expertise in electrochemistry of polyvalent metal ions in glass melts and his achievements in the field of investigation of electrode reactions Fig. 18. Prof. Rüssel – speech at the ceremony for award- in melts at high temperatures are valuable contribution ing him the title Dr. h. c. of the University of Chemical to the development of theoretical redox-chemistry and Technology and Metallurgy, September 29th, 2014. served as a basis for the improvement of many techno-

353 Journal of Chemical Technology and Metallurgy, 50, 4, 2015 logical processes in industry. His contributions to the As last but not least, we would like to acknowl- development of new methods for oriented crystallization edge the help and valuable ideas and suggestions of of glass-ceramic materials such as lithium disilicate, Prof. D.Sc. Yanko Dimitriev during each stage of the phlogopite, apatite and fresnoite have to be mentioned. preparation of this material. His works on surface crystallization processes in oxide We also express our gratitude to the Otto-Schott- glasses are also valuable from practical point of view. Institut for the authorization to use some of the The description of “redox-relaxation” as a third relaxa- materials published at the site of the institute (http:// tion process in glasses in the light of the Marcus theory www.glas1.uni-jena.de/Lehrstuhl+Glaschemie+I/ is another recent key finding which leаds to new insights Research.html). into the fundamental theory of glass thermodynamics at higher temperatures. His work focused on fluorides REFERENCES crystallization from glasses brought to the glass commu- nity not only another type of nanocrystalline advanced 1. C. Rüssel, D. Krauss, K. Ledjeff, Der Einfluss des optical materials but also drew the attention of the sci- Elektrolyten auf die Kinetik der Cr(III)‑Reduktion, in entific world to the idea about the self-constrained and J.W. Schultze (Ed.) Grundlagen von Elektrodenreak- controlled crystallization processes in oxide glasses. The tionen, Dechema Monographie, 102, 1986, 139‑147. successful attempts of his group to synthesize alumino- 2. C. Rüssel, E. Freude, Voltammetric Studies of the silicate glasses of excellent mechanical properties and Redox Behaviour of Various Multivalent Ions in fluorescence lifetimes nearly as good as those of fluoride Soda‑Lime‑Silica Glass Melts, Phys. Chem. Glasses, phosphate glasses deserve special attention. 30, 1989, 62‑68. 3. C. Rüssel, Self Diffusion of Polyvalent Ions in a “I do not make research for money. I am interested Soda‑Lime‑Silica Glass Melt, J. Non‑Cryst. Solids, in science - in what is new and uninvestigated, undis- 134, 1991, 169‑175. covered as knowledge.” 4. C. Rüssel, E. Freude, Voltammetric Studies in a So- da‑Lime‑Silica Glass Melt, Containing Two Different Prof. Christian Rüssel, Jena, July 2014 Polyvalent Ions, Glastech. Ber., 63, 1990, 149‑153. 5. G.B. Balazs, C. Rüssel, Electrochemical Studies of the This vigorous and restless spirit, the versatile and Corrosion of Molybdenum Electrodes in Soda‑Lime focused scientific interests make Christian Rüssel one Glass Melts, J. Non‑Cryst. Solids, 105, 1988, 1‑6. of the most successful contemporary representatives of 6. C. Rüssel, R. Zahneisen, Electrochemical Prepara- applied electrochemistry and physical chemistry of oxide tion of Preceramic Polymers for the Formation of glass melts and solid state oxide glass-ceramics. They Non‑Oxides, J. Electrochem. Soc., 39, 1993, 2424- inspired his numerous diploma- and PhD - students at 2428. the Otto Schott Institute to start a scientific carrier strug- 7. C. Rüssel, A Pyrolytic Route to Fluoride Glasses, I. gling to find their own pathway in science all over the Preparation and Thermal Decomposition of Metal world. That is life worth living! Trifluoro-acetates, J. Non-Cryst. Solids, 152, 1993, 161-166. Acknowledgements 8. V. Geyer, C. Rüssel, Oxynitride Glasses in the Sys- tem Mg‑AI‑Si‑O‑N, Prepared with the Aid of an The authors would like to express their gratitude Electrochemically Derived Polymeric Precursor, J. to Prof. Chrstian Rüssel and all co-workers of the Otto Non‑Cryst. Solids, 149, 1992, 196-202. Schott Institute for Materials Research who contributed 9. U. Wagner, C. Rüssel, A Pyrolytic Route to Fluoride with materials from their archives. Special thanks go to Glasses, II. Preparation of Glasses in the System Mrs. Claudia Siedler, Dr. Doris Möncke, Mrs. Siegrid ZrF4-BaF2-LaF3-AlF3-NaF, J. Non-Cryst. Solids, 152, Keinert, Mrs. Corinna Seelheim, Mr. Berndt Keinert, 1993, 167-171. Mrs. Angela Rüssel and Dr. Wolfgang Wisniewski. 10. D. Benne, R. Keding, C. Rüssel, Redox Equilibria

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⋅ in a Tin-Doped Melt with the Basic Composition Crystals Grown fom a Surface of a 2 BaO TiO2

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11. L. Kido, M. Müller, C. Rüssel, High Tempera- sel, Electron Backscatter Diffraction of BaAl2B2O7 ⋅ ture Spectroscopy of Manganese and Chromium Crystals Grown from the Surface of a BaO Al2O3 ⋅ Doped Glasses with the Basic Composition 16 B2O3 Glass, Crystengcomm, 12, 2010, 3105-3111.

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2005, 523-529. K2O/CaO/CaF2/Al2O3/SiO2 Glasses, Chem. Mater., 12. E. Meechoowas, M. Müller, C. Rüssel, Redox 17, 2005, 5843-5847. Relaxation in Glass Melts Doped With Copper and 25. C. Bocker, C. Rüssel, Self Organized Nano-Crys-

Arsenic, J. Am. Ceram. Soc., 93, 2010, 1032-1038. tallisation of BaF2 from Na2O/K2O/BaF2/Al2O3/SiO2 13. L. Kido, M. Müller, C. Rüssel, Redox Reactions Glasses, J. Europ. Ceram. Soc., 29, 2009, 1221-1225. Occurring During Temperature Change in Soda- 26. N. Tsakiris, P. Agyrakis, I. Avramov, C. Bocker, C. Lime-Silicate Melts Doped with Copper, Tin and Rüssel, Crystal Growth Model with Stress Develop- Antimony or Copper and Tin, Phys. Chem. Glasses, ment and Relaxation, Europ. Phys. Lett., 89, 2010, 45, 2004, 21-26. 18004. 14. R. Keding, C. Rüssel, Oriented Crystallization of 27. S. Bhattacharya, C. Bocker, T. Heil, J. R. Jinschek, T. Fresnoit in an Electric Field. Ber. Bunsenges. Phys. Höche, C. Rüssel, H. Kohl, Experimental Evidence Chem., 100, 1996, 1515-1518. of Self-Limited Growth of Nanocrystals in Glass 15. R. Keding, C. Rüssel, Electrochemical Nucleation Nano Lett., 9, 2009, 2493-2496. for the Preparation of Oriented Glass Ceramics. J. 28. V. S. Raghuwanish, A. Hoell, C. Bocker, C. Rüs- Non-Cryst. Solids, 219, 1997 136-141. sel, Experimental Evidence of a Diffusion Barrier

16. S. Habelitz, G. Carl, C. Rüssel, Processing, Micro- around BaF2 Nano Crystals in a Silicate Glass by structure and Properties of Extruded Mica Glass- ASAXS, Crystengcomm., 14, 2012, 5215-5223. Ceramics, Mater. Sci. Engin., A 307, 2001, 1-14. 29. U. Partenfelder, A. Engel, C. Rüssel, A Pyrolytic 17. C. Moisescu, C. Jana, S. Habelitz, G. Carl, C. Rüs- Route for the Formation of Hydroxyapatite/Fluoroa- sel, Oriented Fluoroapatite Glass Ceramics, J. Non- patite Solid Solutions, J. Mater. Sci.: Materials in Cryst. Solids, 248, 1999, 176-182. Medicine, 4, 1993, 292-295. 18. R. Keding, D. Stachel, C. Rüssel, Oriented Fluor- 30. R. Jaschek, C. Rüssel, Hard Coatings in the System richterite/Diopsid Glass-Ceramics Prepared by Elec- (Ti, Al)(C, N) Prepared by Pyrolysis of Polymeric trochemically Induced Nucleation, J. Non-Cryst. Precursor Films, Surf. Coat. Technol., 45, 1991, Solids, 283, 2001, 137-143. 99‑103. 19. B. R. Durschang, G. Carl, C. Rüssel, I. Gutzow, 31. M. Dittmer, M. Müller, C. Rüssel, Self Organized

Influence of Pressure and Shear Flow on the Crys- Nano Crystallinity in MgO-Al2O3-SiO2 Glasses with

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