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A tribute to George Blasse
A tribute to George Blasse This special issue of the Journal of Luminescence is dedicated to George Blasse on the occasion of his retirement from the chair of Solid State Chemistry at the University of Utrecht in March 1996. The papers collected in this issue are a tribute to George’s lasting contributions to luminescence research. George Blasse was born in 1934 in Amsterdam. He studied chemistry at the University of Amsterdam, where he majored in Physical Chemistry with professor Ketelaar. After his graduation, George fulfilled his military service at the National Defense Laboratories of RVO-TNO, where he was involved in infrared spectroscopy. He next joined Philips Research Laboratories to work in the field of magnetism. A close cooperation between physicists and chemists was strongly encouraged by the directors of the Philips Research Laboratories at that time, professor Casimir and professor Verwey. George’s excellent work on magnetic materials resulted in his PhD thesis: Crystal chemistry and some magnetic properties of mixed metaf oxides with spinel structure. In 1964 he earned his PhD cum laude at the University of Leiden with professor E.W. Gorter as thesis advisor. In 1965, George Blasse entered the field of luminescence. Triggered by the invention of a red emitting Eu3 + phosphor for colour television, George started research on rare earth doped luminescent materials. When he left Philips in 1970, he was author of more than 100 publications, including the famous “Blasse and Bril” papers, and 10 patents on important materials such as: Y,A15012:Ce3 +, NaGdO : Eu3 +, several EL? + phosphors, and the quantum counter NaYF,:Yb3+ ,Er3 + The high quality of his research was recognized in 1970, when he received the Gold Medal of the Royal Dutch Chemical Society, the most prestigious award for young chemists in The Netherlands. In 1970, George Blasse accepted the chair of Solid State Chemistry at the University of Utrecht. Under his guidance the solid state chemistry group worked on luminescence phenomena and luminescent materials. In a short period his group obtained international recognition. More than 50 PhD students received their degree under his supervision. In 1992 George was the officiator at the honorary doctoral ceremony of Dr. P.W. Atkins. George Blasse worked in many areas of luminescence. As examples where his outstanding work has contributed to the understanding of luminescence phenomena and the properties of luminescent materials the following research topics are mentioned: - Explanation of the site-sensitivity of the emission of the Eu 3+ ion in solids and the structure dependence of the quantum efficiency of Eu3+ doped oxides. - Interpretation
of the spectra and the efficiency of Ce3+ and Eu2+ doped host lattices.
- An approach to understand and interpret the luminescence of oxides with d” ions like Ti4+, V5+, Wh+ and the proposal of triplet state emission. Molecular orbital calculations on WOZ- and the transition from localized to delocalized systems. - Fine tuning of the luminescence of the UOZ- group by subtle variations in the surroundings. The observed changes in luminescence properties were supported by quantitative calculations in a configuration coordinate diagram. - Application systems.
of the Dexter model for energy transfer to explain concentration
quenching in many
~ The influence of the dimensionality on energy migration using lD, 2D and 3D Eu3+ compounds. Energy migration in Gd3+ compounds: a quantitative evaluation and application in lamp phosphors of the highest possible efficiency.
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- Interpretation of the luminescence of s2 ions (Bi3+, Sb3+, Pb’+, etc.) in terms of relaxation, space available in the host lattice and the role of charge transfer states. - Quenching of luminescence by electron transfer in solids: a result of close cooperation with coordination chemists. - New phosphors for X-ray (digital) photography. - Nonradiative transitions glasses and crystals.
in glasses and the role of effective charges on the quantum
efficiency in
- Vibronic spectroscopy of rare earth ions and insight in the large variation in electron-phonon strength for rare earth ions.
coupling
This long list is only a selection of his achievements. The work of George Blasse has resulted in more than 700 papers on luminescence in international journals. Each of these papers contains a clear message and new results. A large number of excellent review papers reflect George’s unique insight and overview, and, as a result, are frequently cited. Recently, George, together with B.C. Grabmaier, wrote a book entitled Luminescent Materials (Springer Verlag, Berlin, 1994). In this book, his vast knowledge and long experience in luminescence is manifest in a clear and comprehensive way, to the advantage of many researchers in the field. In the tradition of his early work at Philips, George Blasse’s work straddles the borderline between physics and chemistry and accordingly is characterized by a dual nature. He combined excellent fundamental and successful applied research; he mastered solid state physics and solid state chemistry in a way few other scientists have achieved. George studied fundamental luminescence phenomena and at the same time applied new theories to the development of better luminescent materials. In 1992 he was awarded the Gilles Holst Medal of the Royal Dutch Academy of Sciences for outstanding scientific research connected with possible applications. George Blasse has a thorough understanding of the theoretical aspects of the field (largely explored by physicists) and has used his extensive knowledge and great intuition in solid state chemistry and crystal structures to test theoretical models. George is one of the few scientists who has been able to keep an overview of the complete field of luminescence research. This combined with his encyclopedic knowledge of the literature, makes the work and the position of George Blasse in the luminescence field unique. A striking recent demonstration of his overview over different fields in luminescence research can be found in the field of scintillator materials. In a crisp two page article George Blasse showed that the work of high energy physicists on new scintillator materials ignored extensive knowledge on luminescence under high energy excitation available from studies of cathode ray, X-ray and lamp phosphors. Presently, the rapidly expanding field involving the search for new efficient scintillator materials takes advantage of the approach suggested by George Blasse. Because of his unique overview of the field, his encyclopedic knowledge and his willingness to help, George Blasse was frequently consulted for advice and comments. He has given many invited lectures at conferences and institutes, and has been guest lecturer in Bern, Helsinki, Changchung, and Paris, and five times in Erice. Those who attended one of George’s talks or lectures (and who in the luminescence community has not!) will remember this as a special event. George not only is an excellent scientist, he also has a special gift for teaching. He has a talent to capture the attention of the audience and to explain difficult concepts in a way that everyone can comprehend the essentials. By including results from many different areas in the field, George shows how everything fits together and leaves the audience with a broader understanding of luminescence phenomena. George Blasse’s dedication to science went beyond scientific research. The same disciplined attitude that characterizes his scientific career, he showed in his administrative duties in several research organizations (for
vii
example, the Netherlands Foundation for Chemical Research and the Royal Dutch Academy of Sciences), as a founder and director of the Debye Institute and as a member of the editorial board of eight international journals. This is not the occasion to list all his contributions to promoting science. It is sufficient to mention two important recognitions George Blasse received recently for his contributions towards the progress of science: he has been selected as a member of the European Academy of Sciences and, in April 1996, he was honoured with a high royal decoration for his prominent role in national and international science. Those who have had the privilege to meet George Blasse personally will know that George is an inspiring man with a strong personality. He is loyal, dedicated and shows a personal modesty that characterizes truly great scientists. We have enjoyed working with him in the past and are grateful for what he has accomplished. He is an example to all of us and we sincerely regret that he shows toward his retirement the same dedication he has shown toward his active career. George is now fully enjoying his retired state and the many aspects of life that he did not allow himself time for during his scientific career. We wish him a long and wonderful life in his retirement, and we already miss his input in the luminescence community. It has been a privilege for us to act as guest editors of this special issue of the Journal of Luminescence and to assist in assembling this issue in honour of George Blasse. Andries Meijerink Jaap Dijkhuis Harold de Wijn Editors
of the spectra and the efficiency of Ce3+ and Eu2+ doped host lattices.
- An approach to understand and interpret the luminescence of oxides with d” ions like Ti4+, V5+, Wh+ and the proposal of triplet state emission. Molecular orbital calculations on WOZ- and the transition from localized to delocalized systems. - Fine tuning of the luminescence of the UOZ- group by subtle variations in the surroundings. The observed changes in luminescence properties were supported by quantitative calculations in a configuration coordinate diagram. - Application systems.
of the Dexter model for energy transfer to explain concentration
quenching in many
~ The influence of the dimensionality on energy migration using lD, 2D and 3D Eu3+ compounds. Energy migration in Gd3+ compounds: a quantitative evaluation and application in lamp phosphors of the highest possible efficiency.
vi
- Interpretation of the luminescence of s2 ions (Bi3+, Sb3+, Pb’+, etc.) in terms of relaxation, space available in the host lattice and the role of charge transfer states. - Quenching of luminescence by electron transfer in solids: a result of close cooperation with coordination chemists. - New phosphors for X-ray (digital) photography. - Nonradiative transitions glasses and crystals.
in glasses and the role of effective charges on the quantum
efficiency in
- Vibronic spectroscopy of rare earth ions and insight in the large variation in electron-phonon strength for rare earth ions.
coupling
This long list is only a selection of his achievements. The work of George Blasse has resulted in more than 700 papers on luminescence in international journals. Each of these papers contains a clear message and new results. A large number of excellent review papers reflect George’s unique insight and overview, and, as a result, are frequently cited. Recently, George, together with B.C. Grabmaier, wrote a book entitled Luminescent Materials (Springer Verlag, Berlin, 1994). In this book, his vast knowledge and long experience in luminescence is manifest in a clear and comprehensive way, to the advantage of many researchers in the field. In the tradition of his early work at Philips, George Blasse’s work straddles the borderline between physics and chemistry and accordingly is characterized by a dual nature. He combined excellent fundamental and successful applied research; he mastered solid state physics and solid state chemistry in a way few other scientists have achieved. George studied fundamental luminescence phenomena and at the same time applied new theories to the development of better luminescent materials. In 1992 he was awarded the Gilles Holst Medal of the Royal Dutch Academy of Sciences for outstanding scientific research connected with possible applications. George Blasse has a thorough understanding of the theoretical aspects of the field (largely explored by physicists) and has used his extensive knowledge and great intuition in solid state chemistry and crystal structures to test theoretical models. George is one of the few scientists who has been able to keep an overview of the complete field of luminescence research. This combined with his encyclopedic knowledge of the literature, makes the work and the position of George Blasse in the luminescence field unique. A striking recent demonstration of his overview over different fields in luminescence research can be found in the field of scintillator materials. In a crisp two page article George Blasse showed that the work of high energy physicists on new scintillator materials ignored extensive knowledge on luminescence under high energy excitation available from studies of cathode ray, X-ray and lamp phosphors. Presently, the rapidly expanding field involving the search for new efficient scintillator materials takes advantage of the approach suggested by George Blasse. Because of his unique overview of the field, his encyclopedic knowledge and his willingness to help, George Blasse was frequently consulted for advice and comments. He has given many invited lectures at conferences and institutes, and has been guest lecturer in Bern, Helsinki, Changchung, and Paris, and five times in Erice. Those who attended one of George’s talks or lectures (and who in the luminescence community has not!) will remember this as a special event. George not only is an excellent scientist, he also has a special gift for teaching. He has a talent to capture the attention of the audience and to explain difficult concepts in a way that everyone can comprehend the essentials. By including results from many different areas in the field, George shows how everything fits together and leaves the audience with a broader understanding of luminescence phenomena. George Blasse’s dedication to science went beyond scientific research. The same disciplined attitude that characterizes his scientific career, he showed in his administrative duties in several research organizations (for
vii
example, the Netherlands Foundation for Chemical Research and the Royal Dutch Academy of Sciences), as a founder and director of the Debye Institute and as a member of the editorial board of eight international journals. This is not the occasion to list all his contributions to promoting science. It is sufficient to mention two important recognitions George Blasse received recently for his contributions towards the progress of science: he has been selected as a member of the European Academy of Sciences and, in April 1996, he was honoured with a high royal decoration for his prominent role in national and international science. Those who have had the privilege to meet George Blasse personally will know that George is an inspiring man with a strong personality. He is loyal, dedicated and shows a personal modesty that characterizes truly great scientists. We have enjoyed working with him in the past and are grateful for what he has accomplished. He is an example to all of us and we sincerely regret that he shows toward his retirement the same dedication he has shown toward his active career. George is now fully enjoying his retired state and the many aspects of life that he did not allow himself time for during his scientific career. We wish him a long and wonderful life in his retirement, and we already miss his input in the luminescence community. It has been a privilege for us to act as guest editors of this special issue of the Journal of Luminescence and to assist in assembling this issue in honour of George Blasse. Andries Meijerink Jaap Dijkhuis Harold de Wijn Editors