An Analysis of Glass–Ceramic Research and Commercialization
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An analysis of glass–ceramic research and commercialization Credit: Schott North America Ceran glass-ceramic cooktop by Schott North America. rial. Although Réaumur had succeeded in converting glass into a polycrystalline mate- By Maziar Montazerian, Shiv Prakash Singh, and Edgar Dutra Zanotto rial, unfortunately the new product sagged, deformed, and had low strength because of 4,5 lass has been an important mate- uncontrolled surface crystallization. rial since the early stages of civiliza- The late Stanley Donald Stookey of Corning Glass Works G (now Corning Incorporated, Corning, N.Y.) discovered glass– tion. Glass–ceramics are polycrystalline mate- ceramics in 1953.6–8 Stookey accidentally crystallized Fotoform—a rials obtained by controlled crystallization photosensitive lithium silicate glass containing silver nanopar- ticles dispersed in the glass matrix. From the parent glass of certain glasses that contain one or more Fotoform, Stookey and colleagues at Corning Incorporated, crystalline phases dispersed in a residual which holds the first patent on glass–ceramics, derived the glass– glass matrix. The distinct chemical nature ceramic Fotoceram. The main crystal phases of this glass-ceramic are lithium disilicate (Li2Si2O5) and quartz (SiO2). of these phases and their nanostructures or Since then, the glass–ceramics field has matured with funda- microstructures have led to various unusual mental research and development detailing chemical composi- tions, nucleating agents, heat treatments, microstructures, proper- combinations of properties and applications ties, and potential applications of several materials.3,5,9–15 A recent in the domestic, space, defense, health, elec- article revealed that the term “crystallization” is the top keyword in the history of glass science.16 However, researchers still are tronics, architecture, chemical, energy, and keen to understand further the kinetics of transformation from waste management fields.1–3 glass to a polycrystalline material and to study the associated changes in thermal, optical, electrical, magnetic, and mechanical In 1739, French chemist René-Antoine properties. Nonetheless, several commercial glass–ceramic inno- Ferchault de Réaumur was the first person vations already have been marketed for domestic and high-tech known to produce partially crystallized glass.4 uses, such as transparent and heat-resistant cookware, fireproof doors and windows, artificial teeth, bioactive materials for bone Réaumur heat-treated soda–lime–silica replacement, chemically and mechanically machinable materials, glass bottles in a bed of gypsum and sand and electronic and optical devices. Review articles surveyed the properties and existing uses of for several days, and the process turned glass–ceramics and suggested several possible new applications for the glass into a porcelain-like opaque mate- these materials.9–17 Here we report on the results of a statistical 30 www.ceramics.org | American Ceramic Society Bulletin, Vol. 94, No. 4 Capsule summary BACKGROUND ANALYSIS KEY POINT Glass–ceramics are polycrystalline materials Through a database search of published papers The field of glass–ceramics has grown during the derived from glass with distinct properties that and filed patents, the authors statistically evalu- past 60 years and continues to show signs of ex- give them unique applications in domestic, ate the evolution of scientific and technological ponential growth. Analysis of patent applications space, defense, health, electronics, architecture, research and development of glass–ceramics has identified a few areas of promising growth chemical, energy, and waste management. during the past 60 years. that may serve as a guide for future commercial endeavors in this field of unique materials. search evaluating the evolution of scientific words in patent titles from FPO records glass–ceramic publications lies between and technological research and develop- from January 2001—December 2013. In these two extremes. Figure 1 shows that, ment of glass–ceramics during the past this case, we searched granted patents using either search strategy, the number 60 years. We made an electronic search and patent applications and found 1,964 of articles shows some annual fluctua- of published research articles, granted records. After sorting and eliminating sis- tion, although both strategies reveal an patents, and patent applications since the ter patents submitted to different offices, exponential increase. Currently, about discovery of glass–ceramics in 1953. we identified 1,000 single granted patents 500–800 papers on glass–ceramics are For a more in-depth assessment and applications, which we categorized published annually. of recent trends and developments manually according to main property or The 40 most prolific authors (not shown in this field, we manually searched proposed use of the glass–ceramic. here) include researchers with 40–130 and reviewed 1,000 granted patents published articles on several aspects of and applications filed during the past Published glass–ceramic papers glass–ceramic materials. The first paper on decade. Here we break down these Searching Scopus for keywords only glass–ceramics listed in the Scopus database numbers into main property classes in article titles provided cleaner results is authored by W.W. Shaver and S.D. (thermal, mechanical, optical, electrical, than searching within abstracts, but this Stookey in 1959, which proposes the name etc.) and proposed applications. The limited search failed to capture all glass– of Pyroceram for the new class of materi- overall objective of this short article is ceramic publications. The search yielded als.18 A second paper, authored by G.W. to give students, academics, and indus- 7,040 papers, which, thus, represents McLellan in the same year, discusses pos- trial researchers some insight about the only a lower bound. Conversely, expand- sible applications of glass–ceramics in the evolution of and perspectives for appli- ing the selected keyword search to article automotive industry.19 cations of this class of materials. We titles, abstracts, and keywords yielded Figure 2 reveals the number of publica- hope it also may be a useful source of 12,806 papers, including several that are tions authored by researchers with par- ideas for new research projects. only minimally related to glass–ceram- ticular affiliations, most of which are uni- ics. Therefore, the actual number of versities. Kyoto University in Japan holds Database search We surveyed the Scopus Elsevier, Free Patents Online (FPO), and Derwent World Patents Index (DWPI) databases for patents and papers published in glass–ceramic science and technology. We searched the Scopus database for scientific publications 1955—2014 using the keywords “sittal”, “vitroceramic*”, “glass–ceramic*”, or “glass ceramic*” in the article title or, in a separate search, in the title, abstract, and keywords. Number of papers Keywords “glass–ceramic” and “glass ceramic” predominate by a large margin. We then sorted articles by publication year, affiliation, and country. Additionally, we extracted DWPI records of granted patents by searching for keywords “glass–ceramic*”or “glass ceramic*” in patent titles from 1968—July Year 2014. We ranked the number of pub- Credit: E.D. Zanotto lished patents per year as well as the most Figure 1. Number of published articles per year extracted from the Scopus database by prolific companies from the records. searching the keywords “sittal”, “vitroceramic*”, “glass–ceramic*”, or “glass ceramic*” Further, we searched the same key- in article titles (blue) or in article titles, abstracts, or keywords (red). American Ceramic Society Bulletin, Vol. 94, No. 4 | www.ceramics.org 31 An analysis of glass–ceramic research and commercialization patents. However, this particular search engine provided no other pos- sible search strategies. With this restrictive search strategy, the total number of glass–ceramics patents granted—which thus represents a minimum—up to December 2013 is 4,882. Although granted patents have Affiliation fluctuated somewhat over the years, the number has steadily grown in the past two decades (Figure 3). During 1975– 1979 and 2003–2008, total patents declined monotonically, whereas the number increased 1994–1998. Overall, about 220 new patents are granted each Number of papers year. Our analysis reveals that glass– Credit: E.D. Zanotto Figure 2. Total glass–ceramic publications in the Scopus database from 1955–July 2014, ceramic technology is growing rapidly sorted by affiliation. Counted articles contained keywords “sittal”, “vitroceramic*”, and several potential new products are “glass–ceramic*”, or “glass ceramic*” in the article title. emerging every year. the top position with 157 articles, fol- research with 1,557 papers, followed by Further, we searched DWPI for key- lowed by several Chinese and European researchers from the U.S. (718 papers), words “glass–ceramic*” or “glass ceram- universities and two institutions in emerg- Japan (663 papers), Germany (462 papers), ic*” in patent titles and found that sev- ing countries—Iran University of Science and the United Kingdom (404 papers). eral companies around the world manu- and Technology in Tehran, Iran, and Most countries in this ranking are industri- facture glass–ceramic products (Table 1). the National Research Center in Cairo, ally developed. However, it is somewhat Several companies hold glass–ceramics Egypt. The only company in this ranking surprising that several