Dear Colleagues,

This Special Issue is dedicated to the domain of transparent ceramics ( TCs); passive or active ones (owing to controlled doping—able to induce designed spectral behavior). It intends to treat topics such as the optimization of all aspects of TC fabrication-related engineering and the introduction of new processing techniques. There is also interest in studies devoted to performance level enhancement of current products (commercial and in prototype stage), relevant characterization techniques (concerning fabrication or performance estimation), and new applications. In many cases, the usefulness of a TC is owed to an adequate design of the dopants package and/or a suitable matching of it with the transparent host. Therefore, works dealing with theoretical and/or applied transition metal cations (TMC), rare-earth (RE) spectroscopy, optical, EPR, Raman, etc., are welcome. So are results regarding host characterization refinements—such as more accurate site symmetry determinations—relevant for dopant accommodation in the host lattice.

The issue also intends to honor Dr. Adrian Goldstein (former head of the Israel Ceramics and Silicates Institute) for his significant contribution to the development of the TC domain. Below, we offer a list of some of the topics studied by the researcher honored. For instance, together with Dr. Andreas Krell (former IKTS-Dresden senior researcher), Dr. Goldstein realized the fact that full ceramics sinterability is obtained more as a result of actions taken in the stage of green-body forming than during sintering. Thus, he demonstrated that an ordered array (obtained by slow gravitational or fast centrifugal deposition) of amorphous micron size cvasi-monodisperse—spherical micron silica particles arranged in a compact packing maintained over large specimen volumes—allows densification fast enough (obtained by MW heating) to generate transparent bulk specimens without crystallization. Arranging, in the same manner, suitable MgAl₂O₄ powder, highly transparent specimens were obtained via sintering (pressureless + HIP) at temperatures around 1300 ^oC, viz. many hundreds of degrees lower than is necessary to densify conventional green bodies. He also discovered that, in phosphate glasses, the addition of alkaline-earth metals, as opposed to alkaline ones, reduces the electron donor ability (basicity) of oxide ions. Based on this effect, Cu0-based phosphate stable glasses could be obtained without Sn addition and a striking stage. An interesting finding relates to the accommodation of d1 type cations in oxide glasses. Many such ions (Ti³⁺, VO²⁺, Nb⁴⁺, Mo⁵⁺ and W⁵⁺) have in common the tendency to form C4v complexes in oxide glass hosts; the tendency increases with an increase of the oxidation state. Dr. Adrian Goldstein was the first (1998) to obtain transparent spinel via MW sintering (followed by HIPing) and ZnAl₂O₄ spinel as a transparent ceramic. He identified the main parasitic, reducing incident EMR beams intensity when interacting with spinel or YAG. He determined the mechanisms (promoting or impeding densification) operating when LiF is added to spinel for full densification via hot pressing. Dr. Goldstein also participated in the development of saturable absorber type, Co²⁺ based Q-switches for Er³⁺ lasers. Regarding the interaction of transition metal dopants in glasses, he discovered a redox interaction between Cr³⁺ and Cu²⁺.

The list of his publications includes, among others, an invited paper on transparent ceramics (J. Amer. Ceram. Soc. 2016) and eight invited lectures on the same topic. A more extensive review of the domain was offered in the book written by Dr. Adrian Goldstein:

Goldstein A., Krell A. and Burshtein Z. “Transparent Ceramics: Materials, Engineering and Applications”., J. Wiley and Sons, N.Y., 2020

Contributions, regarding the topics listed at the start of this document, are invited for this Special Issue “Transparent Ceramics—a Theme Issue in Honor of Dr. Adrian Goldstein”.

Prof. Dr. Yiquan Wu
Guest Editor

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