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www.ceramics.org | American Ceramic Society Bulletin, Vol. 94, No. 4
30
An analysis of
glass–ceramic research
and commercialization
By Maziar Montazerian, Shiv Prakash Singh,
and Edgar Dutra Zanotto
G
lass has been an important mate-
rial since the early stages of civiliza-
tion. Glass–ceramics are polycrystalline mate-
rials obtained by controlled crystallization
of certain glasses that contain one or more
crystalline phases dispersed in a residual
glass matrix. The distinct chemical nature
of these phases and their nanostructures or
microstructures have led to various unusual
combinations of properties and applications
in the domestic, space, defense, health, elec-
tronics, architecture, chemical, energy, and
waste management fields.
1–3
In 1739, French chemist René-Antoine
Ferchault de Réaumur was the first person
known to produce partially crystallized glass.
4
Réaumur heat-treated soda–lime–silica
glass bottles in a bed of gypsum and sand
for several days, and the process turned
the glass into a porcelain-like opaque mate-
rial. Although Réaumur had succeeded in
converting glass into a polycrystalline mate-
rial, unfortunately the new product sagged,
deformed, and had low strength because of
uncontrolled surface crystallization.
4,5
The late Stanley Donald Stookey of Corning Glass Works
(now Corning Incorporated, Corning, N.Y.) discovered glass–
ceramics in 1953.
6–8
Stookey accidentally crystallized Fotoform—a
photosensitive lithium silicate glass containing silver nanopar-
ticles dispersed in the glass matrix. From the parent glass
Fotoform, Stookey and colleagues at Corning Incorporated,
which holds the first patent on glass–ceramics, derived the glass–
ceramic Fotoceram. The main crystal phases of this glass-ceramic
are lithium disilicate (Li
2
Si
2
O
5
) and quartz (SiO
2
).
Since then, the glass–ceramics field has matured with funda-
mental research and development detailing chemical composi-
tions, nucleating agents, heat treatments, microstructures, proper-
ties, and potential applications of several materials.
3,5,9–15
A recent
article revealed that the term “crystallization” is the top keyword
in the history of glass science.
16
However, researchers still are
keen to understand further the kinetics of transformation from
glass to a polycrystalline material and to study the associated
changes in thermal, optical, electrical, magnetic, and mechanical
properties. Nonetheless, several commercial glass–ceramic inno-
vations already have been marketed for domestic and high-tech
uses, such as transparent and heat-resistant cookware, fireproof
doors and windows, artificial teeth, bioactive materials for bone
replacement, chemically and mechanically machinable materials,
and electronic and optical devices.
Review articles surveyed the properties and existing uses of
glass–ceramics and suggested several possible new applications for
these materials.
9–17
Here we report on the results of a statistical
Ceran glass-ceramic cooktop by Schott North America.
Credit: Schott North America
31
American Ceramic Society Bulletin, Vol. 94, No. 4 | www.ceramics.org
search evaluating the evolution of scientific
and technological research and develop-
ment of glass–ceramics during the past
60 years. We made an electronic search
of published research articles, granted
patents, and patent applications since the
discovery of glass–ceramics in 1953.
For a more in-depth assessment
of recent trends and developments
in this field, we manually searched
and reviewed 1,000 granted patents
and applications filed during the past
decade. Here we break down these
numbers into main property classes
(thermal, mechanical, optical, electrical,
etc.) and proposed applications. The
overall objective of this short article is
to give students, academics, and indus-
trial researchers some insight about the
evolution of and perspectives for appli-
cations of this class of materials. We
hope it also may be a useful source of
ideas for new research projects.
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.
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
2014. We ranked the number of pub-
lished patents per year as well as the most
prolific companies from the records.
Further, we searched the same key-
words in patent titles from FPO records
from January 2001—December 2013. In
this case, we searched granted patents
and patent applications and found 1,964
records. After sorting and eliminating sis-
ter patents submitted to different offices,
we identified 1,000 single granted patents
and applications, which we categorized
manually according to main property or
proposed use of the glass–ceramic.
Published glass–ceramic papers
Searching Scopus for keywords only
in article titles provided cleaner results
than searching within abstracts, but this
limited search failed to capture all glass–
ceramic publications. The search yielded
7,040 papers, which, thus, represents
only a lower bound. Conversely, expand-
ing the selected keyword search to article
titles, abstracts, and keywords yielded
12,806 papers, including several that are
only minimally related to glass–ceram-
ics. Therefore, the actual number of
glass–ceramic publications lies between
these two extremes. Figure 1 shows that,
using either search strategy, the number
of articles shows some annual fluctua-
tion, although both strategies reveal an
exponential increase. Currently, about
500–800 papers on glass–ceramics are
published annually.
The 40 most prolific authors (not shown
here) include researchers with 40–130
published articles on several aspects of
glass–ceramic materials. The first paper on
glass–ceramics listed in the Scopus database
is authored by W.W. Shaver and S.D.
Stookey in 1959, which proposes the name
of Pyroceram for the new class of materi-
als.
18
A second paper, authored by G.W.
McLellan in the same year, discusses pos-
sible applications of glass–ceramics in the
automotive industry.
19
Figure 2 reveals the number of publica-
tions authored by researchers with par-
ticular affiliations, most of which are uni-
versities. Kyoto University in Japan holds
Capsule summary
BACKGROUND
Glass–ceramics are polycrystalline materials
derived from glass with distinct properties that
give them unique applications in domestic,
space, defense, health, electronics, architecture,
chemical, energy, and waste management.
ANALYSIS
Through a database search of published papers
and filed patents, the authors statistically evalu-
ate the evolution of scientific and technological
research and development of glass–ceramics
during the past 60 years.
KEY POINT
The field of glass–ceramics has grown during the
past 60 years and continues to show signs of ex-
ponential growth. Analysis of patent applications
has identified a few areas of promising growth
that may serve as a guide for future commercial
endeavors in this field of unique materials.
Figure 1. Number of published articles per year extracted from the Scopus database by
searching the keywords “sittal”, “vitroceramic*”, “glass–ceramic*”, or “glass ceramic*”
in article titles (blue) or in article titles, abstracts, or keywords (red).
Number of papers
Year
Credit: E.D. Zanotto
www.ceramics.org | American Ceramic Society Bulletin, Vol. 94, No. 4
32
An analysis of glass–ceramic research and commercialization
the top position with 157 articles, fol-
lowed by several Chinese and European
universities and two institutions in emerg-
ing countries—Iran University of Science
and Technology in Tehran, Iran, and
the National Research Center in Cairo,
Egypt. The only company in this ranking
is Corning Incorporated, and it is no sur-
prise that most scientific research in this
field is conducted in academia. However,
patent rankings tell a different story.
In terms of statistics by country,
Chinese investigators lead glass–ceramic
research with 1,557 papers, followed by
researchers from the U.S. (718 papers),
Japan (663 papers), Germany (462 papers),
and the United Kingdom (404 papers).
Most countries in this ranking are industri-
ally developed. However, it is somewhat
surprising that several emerging countries,
such as India, Brazil, Egypt, Iran, Turkey,
and Romania, also are well ranked.
Patents for glass–ceramics
In addition to publications related to
glass–ceramics, analysis of the status of
glass–ceramic
patents com-
piles an overall
view of techno-
logical develop-
ments in the
field. Similar
to searching
the publica-
tions database,
searching the
DWPI patent
database for key-
words “glass–
ceramic*”or
“glass ceram-
ic*” only in
patent titles
provided clean-
er results, but
this limited
search failed
to capture all
glass–ceramic
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
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
year. Our analysis reveals that glass–
ceramic technology is growing rapidly
and several potential new products are
emerging every year.
Further, we searched DWPI for key-
words “glass–ceramic*” or “glass ceram-
ic*” in patent titles and found that sev-
eral companies around the world manu-
facture glass–ceramic products (Table 1).
Several companies hold glass–ceramics
patents, but only some are commercial-
izing such products. Likewise, some com-
panies manufacture and sell commercial
glass–ceramics, although they are not
among the top patenting companies.
Figure 4 shows the 20 most prolific
companies from DWPI that were grant-
ed glass–ceramic patents in 1968–2014.
Schott AG, Corning Incorporated,
Kyocera, and Nippon Electric Glass hold
the top four positions. All others are
Japanese, German, or American compa-
nies, with the exception of dental glass–
ceramic company Ivoclar Vivadent from
Liechtenstein. Some companies, such as
Owens–Illinois, were very active during
the 1970s—when they filed several pat-
ents on glass–ceramics—but then halted
their activity in this field. However, most
of these companies still engage in R&D
and manufacture various types of com-
mercial glass–ceramics.
5,9
Commercial applications of
glass–ceramics
DWPI allows automatic breakdown of
granted patents per field, which reveals
a wide spectrum of knowledge, spanning
from traditional fields, such as chemis-
try, engineering, and materials science,
to unexpected areas, such as polymer
Number of patents
Year
Figure 3. Number of patents granted per year, extracted from the
DWPI database by searching for keywords “glass–ceramic*” or
“glass ceramic*” in the patent title.
Credit: E.D. Zanotto
Figure 2. Total glass–ceramic publications in the Scopus database from 1955–July 2014,
sorted by affiliation. Counted articles contained keywords “sittal”, “vitroceramic*”,
“glass–ceramic*”, or “glass ceramic*” in the article title.
Number of papers
Affiliation
Credit: E.D. Zanotto
33
American Ceramic Society Bulletin, Vol. 94, No. 4 | www.ceramics.org
science, food science, and environmental
fields (Figure 5).
For a more comprehensive view, we
manually searched the FPO database,
which allows separate searching of
granted patents and patent applications,
by reading abstracts (and some text) of
about 2,000 of the most recently filed
and granted patents.
Glass–ceramics with specific properties,
such as thermal (e.g., low thermal expan-
sion, insulating, high thermal stability, etc.),
electrical, (e.g., high ionic conductivity),
or optical (e.g., high transparency, high
luminescence efficiency) properties, have
attracted considerable attention from indus-
tries and technologists in the past decade.
This special interest has resulted in more
than 550 patents on various glass–ceramics
intended for electronic components, wiring
board substrates, cooktop panels, insulators,
sealants, heat reflector substrates, and more
(Table 2). Some patents also have been
granted for glass–ceramics with architec-
tural, biological, magnetic, armor, energy,
nuclear, and waste immobilization applica-
tions and for applications in combined
fields, such as electrooptics.
Overall trends in current patent appli-
cations—which are more recent than
granted patents—are decreased electrical,
electronic, and magnetic applications
and increased dental, biomedical, opti-
cal, energy, chemical, waste manage-
ment, refractory, and “other” applica-
tions for glass–ceramics. These results
suggest that those areas are potential
thrust fields for advanced technology.
The above-listed trend applications are
in line with current demands of new
products, suggesting prospects for indus-
trial growth in these areas.
Future growth
A great deal already is known about
glass–ceramics, but several challenges and
opportunities in glass–ceramics research
and development remain to be explored
for desired properties and new applica-
tions of these materials. A few important
areas for further exploration follow.
Fundamental and technological studies
• Search for new or more potent
nucleating agents for the synthesis of
glass–ceramics using data mining tech-
niques, theoretical equations, and mod-
Table 1. Prominent companies and some of their glass–ceramic inventions
5,9–11
Company Product Crystal type Applications
Schott, Germany
Foturan Lithium silicate Photosensitive and etched patterned materials
Zerodur β-quartz(ss) Telescope mirrors
Ceran/Robax β-quartz(ss) Cookware, cooktops, and oven doors
Nextrema Lithium aluminosilicate Fireproof window and doors
Corning Inc., U.S.
Pyroceram β-spodumene(ss) Cookware
Fotoform/Fotoceram
Lithium silicate Photosensitive and etched patterned materials
Cercor β-spodumene(ss) Gas turbines and heat exchangers
Centura Barium silicate Tableware
Vision β-quartz(ss) Cookware and cooktops
9606 Cordierite Radomes
MACOR Mica Machinable glass–ceramics
9664 Spinel–enstatite Magnetic memory disk substrates
DICOR Mica Dental restorations
Nippon Electric
Glass, Japan
ML-05 Lithium disilicate Magnetic memory disk substrates
Neoparies β-wollastonite Architectural glass–ceramics
Firelite β-quartz(ss) Architectural fire-resistant windows
Neoceram N-11 β-spodumene(ss) Cooktops and kitchenware
Narumi β-quartz(ss) Low-thermal-expansion glass–ceramics
Neoceram N-0 β-quartz(ss) Color filter substrates for LCD panels
Cerabone A-W Apatite–wollastonite Bioactive implants
Ivoclar Vivadent IPS Series Leucite/lithium Dental restorations
AG, Liechtenstein silicate/leucite–apatite
Eurokera, U.S./France
Keralite β-quartz(ss) Fire-resistant windows and doors
Eclair β-quartz(ss) Transparent architectural glass–ceramics
Keraglas β-quartz(ss) Cookware and cooktops
Asahi Glass Co., Japan Cryston β-wollastonite Architectural glass–ceramics
Kyushu Co., Japan Crys-Cera Calcium metaphosphate Dental restorations
Leitz, Wetzlar Co., Germany Ceravital Apatite Bioactive glass–ceramics
Ohara Inc., Japan
LiC-GC Nasicon(ss) Lithium-conducting glass–ceramics
TS-10 Lithium disilicate Magnetic memory disk substrates
Owens-Illinois, U.S. Cer-Vit β-spodumene(ss) Cookware and kitchenware
Pentron Ceramic Inc., U.S. 3G OPC Lithium disilicate Dental crowns
PPG, U.S. Hercuvit β-spodumene(ss) Cookware and domestic-ware
Vitron, Germany
Bioverit series and Mica/mica–apatite/ Biomaterials and machinable glass–ceramics
Vitronit phosphate type
Sumikin Photon, Japan Fotovel/ Photoveel Mica type Dental and insulator materials
Yata Dental MFG Co., Japan Casmic Apatite–magnesium titanate Bioactive and dental glass–ceramics
Company name
Number of patents
Figure 4. Twenty com-
panies with the most
glass–ceramic patents
granted 1968–2014,
extracted from
records in the DWPI
database by search-
ing for the keywords
“glass–ceramic*” or
“glass ceramic*” in
the title.
www.ceramics.org | American Ceramic Society Bulletin, Vol. 94, No. 4
34
An analysis of glass–ceramic research and commercialization
eling rather than empirical trials;
• Development of stronger, chemically
resistant chalcogenide glass–ceramics with
novel electric and optical properties;
• Development of new or improved
crystallization processes, such as microwave
heating, biomimetic assemblage of crystals,
textured crystallization, laser crystallization,
and electron beam crystallization;
• Deeper understanding and control
of photothermal-induced nucleation;
• Engineering adequate matrices for
development of hierarchical nanostruc-
tured glass–ceramics based on variations
in size, distribution, and composition of
nanoscale crystals;
• Confinement of the glassy phase
(nanoglass) within the glass–ceramic
matrix by reverse engineering based on
novel synthesis processes;
• Fabrication of 2-D and 3-D single
crystals within glass matrices via direct
laser heating or photothermal-induced
crystallization; and
• Understanding the role of the
residual glass phase in the properties of
glass–ceramics.
Desired material properties
• Highly bioactive glass–ceramics for
tissue engineering or drug delivery and for
preventive treatments that slow down dete-
rioration and maintain health of tissues;
• Development of harder, stiffer,
stronger, and tougher glass-ceramics, for
instance, HV > 11 GPa, E > 150 GPa,
four-point-fracture strength > 400 MPa,
and K
IC
>3 MPa∙m
1/2
;
• Nanocrystalline glass–ceramics with
greater transparency in the ultraviolet,
visible, or infrared spectral regions;
• Highly transparent and efficient
scintillator glass–ceramics; and
• Glass–ceramics with ionic conduc-
tivities >10
–3
S/cm.
Possible applications
• Glass–ceramics for solar cell appli-
cations with improved optical, thermal,
electrical, and mechanical properties
for use as substrates, matrices, and solar
light concentrators;
• Glass–ceramics as self-healing seal-
ant materials with high longevity for fuel
cells and electronic devices;
• Glass–ceramics as smart architectur-
al building materials with antifungal and
self-cleaning properties; automatic energy
generators for building energy consump-
tion, multisensor security, and antifire
systems; and materials with dynamic
color-changing abilities;
• Glass–ceramic compositions for
immobilization of nuclear waste products;
• Glass–ceramics to replace existing
materials (polymers) currently used in
a variety of electronic products, such as
computers, mobile phones, IC chips,
and mother boards, to address future
environmental problems associated with
electronics waste;
• Glass–ceramics for nanopatterning
and nanolithography in high-tech materials;
• Glass–ceramics for treatment of cancer
using thermal or photosensitive therapies;
• Glass–ceramics for components
in space research and similar sophisti-
Table 2. Proposed uses for glass–ceramics in patent applications and granted patents in
FPO database from January 2001–July 2014
Subject Number of patents Proposed uses
Applications Granted
Thermal 141 145 Cookware, cooktops, hot plates, low-thermal-expansion glass–ceramics, sealants,
and fireproof windows and doors
Electrical 52 95 Solid electrolytes, lithium-ion-conducting glass–ceramics, and semiconductor substrates
Electronics 24 96 Electronic components, substrates for electronic devices, and plasma display panels
Optical 63 55 Transparent glass–ceramics, luminescent glass–ceramics, colored glass–ceramics,
lasers, lens, and mirrors
Dental 38 21 Dental restorations and dental prosthetic devices
Mechanical 29 30 Abrasives, machinable glass–ceramics, and high-strength glass–ceramics
Chemical 25 23 Catalytically active glass–ceramics, photocatalyst supports, corrosion-resistant glass–
ceramics, ion-exchanged glass–ceramics, and glues
Architecture 15 13 Decorative substrates and building construction glass–ceramics
Biology 17 10 Bioactive scaffolds, antimicrobial glass–ceramics, antiinflammatory glass–ceramics,
and glass–ceramic powders for cosmetics
Energy 10 7 SOFCs, LEDs, and solar cells
Magnetic 6 11 Magnetic head actuators, magnetic information storage media, and substrates for
magnetic storage devices
Armor 8 7 Bulletproof and missileproof glass–ceramic components and bulletproof vests
Subject area
Number of patents
Figure 5. DWPI database breakdown of number of patents granted in various fields
by searching keywords “glass–ceramic*” or “glass ceramic*” in patent titles from
1968–2014.
Credit: E.D. Zanotto
35
American Ceramic Society Bulletin, Vol. 94, No. 4 | www.ceramics.org
cated environments;
• Ultrafast crystallizable chalcogenide
glass–ceramics for rewritable optical
disks and PRAM devices; and
• Glass–ceramics with low thermal
conductivity, high electrical conductivity,
and adequate Seebeck coefficient developed
into thermoelectric power generators, which
could produce renewable and sustainable
energy in vehicle exhaust manifolds, furnace
exhausts, and building windows.
In addition, other unexpected applica-
tions will probably emerge that require
new combinations of material properties.
Past growth in research expected
to continue
Statistics on published scientific
articles and patents indicate that glass–
ceramic research has grown exponential-
ly during the past 60 years, with no signs
of slowing down. The above analysis pro-
vides an overall picture in terms of num-
bers as well as traditional and new areas
of applications for the advancement of
glass-ceramics. Commercially successful
products include those intended for
domestic and high-tech applications—
such as cookware, chemically or mechan-
ically machinable materials, telescope
mirrors, hard-disk substrates, cooktop
plates, artificial bones, and dental pros-
theses—but the breadth of uses proposed
in patents is much wider. Analyses of
patent applications of glass–ceramics
versus number of granted patents in the
past decade reveal significant growth in
dental, biomedical, waste management,
and optical applications.
We hope this report serves as a
motivation and guide for students, pro-
fessors, technologists, and researchers
when thinking of future research direc-
tions and, most importantly, encourages
researchers to dig deeper to find new
glass–ceramic compositions, nucleating
agents, and heat treatments that lead to
novel structures and properties. Such
considerations may result in materials
with uniquely organized nanostructures
or microstructures or with useful combi-
nations of properties that are well suited
for new applications.
Acknowledgments
The authors dedicate this article to
S.D. Stookey—although he passed away
on November 4, 2014, his important dis-
coveries and legacy will remain forever.
The authors thank the São Paulo
Research Foundation for financial sup-
port of this research project, and they
also acknowledge Brazil’s National
Council for Scientific and Technological
Development and The World Academy
of Sciences for Ph.D. fellowships granted
to Maziar Montazerian. The authors also
appreciate the critical comments of Mark
Davis, George Beall, and Atiar Rahaman
Molla. Edgar Dutra Zanotto is indebted
to the knowledgeable members of the
Crystallization and Glass–Ceramics
Committee of the International
Commission on Glass for enlightening
discussions during the past 30 years.
About the authors
All authors are from the Department
of Materials Engineering at the
Center for Research, Technology, and
Education in Vitreous Materials at
Federal University of São Carlos, Brazil.
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n
Realizing the potential of glass–ceramics in industry
by John C. Mauro, Corning Incorporated
The accidental discovery of glass–ceramics by
S. Donald Stookey in 1953 revolutionized the glass
industry by enabling new properties, such as ex-
ceptionally high fracture toughness and low thermal
expansion coefficient compared with traditional
glasses. Although glassy materials are noncrystalline
by definition, glass–ceramics are based on controlled
nucleation and growth of crystallites within a glassy
matrix. Concentration, size, and chemistry of the
crystallites can be controlled through careful design
of the base glass chemistry and the heat-treatment
cycle used for nucleation and crystal growth. These
composition and process parameters give new
dimensions for optimizing the properties of industrial
glass–ceramics.
Table 1 provides an excellent summary of com-
mercialized glass–ceramic products. The success of
these products is based on achieving unique com-
binations of attributes, including appropriate optical,
thermal, mechanical, and biological properties, often
which cannot be achieved by an “ordinary” non-
crystalline glass. For many of these products, such
as MACOR and dental glass–ceramics, forming and
machining behavior of the glass–ceramic materials
are also of critical concern.
Successful design of next-generation indus-
trial glass–ceramic products should be aided by
a renewed focus on the fundamental physics and
chemistry governing these high-tech materials.
Although the thermodynamic and kinetic aspects
of crystallization are of the utmost importance
for designing industrial materials, there remains
insufficient theoretical understanding of these basic
processes in glass–ceramics. Future development of
new theoretically rigorous modeling capabilities will
hopefully enable quantitatively accurate predictions
of glass–ceramic microstructures and properties.
A detailed understanding of glass–ceramic materials
is an exceptionally challenging problem, especially
for many-component oxide systems that are the
basis for most industrial glass–ceramic products.
However, this presents a unique opportunity to build
a solid foundation for realizing the many exciting fu-
ture applications of glass–ceramics described in the
accompanying article and to train the next generation
of industrial glass–ceramic scientists.