Editor
Ru-Shi Liu

Phosphors, Up Conversion Nano
Particles, Quantum Dots and
their Applications
Volume 2

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Editor
Ru-Shi Liu
Department of Chemistry, National Taiwan University, Taipei,
Taiwan
Department of Mechanical Engineering and Graduate Institute of
Manufacturing Technology, National Taipei University of
Technology, Taipei, Taiwan

ISBN 978-981-10-1589-2 e-ISBN 978-981-10-1590-8
DOI 10.1007/978-981-10-1590-8
Library of Congress Control Number: 2016943379
© Springer Science+Business Media Singapore 2016
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The use of general descriptive names, registered names,
trademarks, service marks, etc. in this publication does not imply,
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even in the absence of a specific statement, that such names are
exempt from the relevant protective laws and regulations and
therefore free for general use.
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Preface
This book is divided into two volumes. In Volume 1, we start
with an introduction to the basic properties of luminescent
materials (phosphors), before addressing the principle of energy
transfer and pressure effect of phosphor. Moreover, we present
the theoretical first-principles calculation of luminescent
materials. After having established a basic understanding of

phosphors, we then discuss a variety of phosphors of oxides,
nitrides, (oxy)nitrides, fluorides, etc. In Volume 2, we shift the
focus to the applications of phosphors in light-emitting diodes,
field emission displays, agriculture, solar spectral convertors and
persistent luminescent materials. We then demonstrate through the
basic upconversion nanoparticles their applications in
biomedical contexts. Lastly, we introduce readers to the basics
and applications of quantum dots.
Taken together, the two volumes offer essential insights on the
basics and applications of phosphor at the bulk and nanoscale.
Ru-Shi Liu
Taipei, Taiwan

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Contents
1 Exploration of New Phosphors Using a Mineral-Inspired
Approach in Combination with Solution Parallel Synthesis
Masato Kakihana, Hideki Kato, Makoto Kobayashi,
Yasushi Sato, Koji Tomita and Tetsufumi Komukai
2 Phosphors for Field Emission Display: Recent Advances in
Synthesis, Improvement, and Luminescence Properties
Guogang Li and Jun Lin
3 Phosphors with a 660-nm-Featured Emission for LED/ LD
Lighting in Horticulture
Dajian Wang, Zhiyong Mao and B. D. Fahlman
4 The Application of Phosphor in Agricultural Field
Xiaotang Liu, Bingfu Lei and Yingliang Liu
5 Rare Earth Solar Spectral Convertor for Si Solar Cells

Jing Wang, Xuejie Zhang and Qiang Su
6 Persistent Luminescent Materials
Yingliang Liu and Bingfu Lei
7 Foundations of Up-conversion Nanoparticles
Song Wang and Hongjie Zhang
8 Lanthanide-Doped Upconversion Nanoprobes
Datao Tu, Wei Zheng, Ping Huang and Xueyuan Chen
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9 Lanthanide-Doped Core–Shell Upconversion
Nanophosphors
Tianying Sun and Feng Wang
10 Upconversion Luminescence Behavior of Single
Nanoparticles
Jiajia Zhou and Jianrong Qiu
11 Persistent Luminescence Nanomaterials for Biomedical
Applications: A Quick Grasp of the Trend
Wai-Lun Chan, ZhenYu Liu and Ka-Leung Wong
12 Upconversion Nanoparticles for Bioimaging
Xiangzhao Ai, Junxin Aw and Bengang Xing
13 Upconversion Nanoparticle as a Platform for
Photoactivation
Pounraj Thanasekaran, Hua-De Gao and Hsien-Ming Lee
14 Foundations of White Light Quantum Dots
Shu-Ru Chung
15 Cadmium Free Quantum Dots: Principal Attractions,
Properties, and Applications
Anush Mnoyan, Yonghee Lee, Hankyeol Jung, Somang Kim
and Duk Young Jeon

16 Synthesis of InP Quantum Dots and Their Application
Hung-Chia Wang and Ru-Shi Liu
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17 Carbon Nitride Quantum
Dots and Their Applications


17 Carbon Nitride Quantum Dots and Their Applications
Ming-Hsien Chan and Ru-Shi Liu
18 Luminescent Materials for 3D Display Technology
Haizheng Zhong, Ziwei Wang, Wengao Lu, Juan Liu and
Yongtian Wang

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© Springer Science+Business Media Singapore 2016
Ru-Shi Liu (ed.) Phosphors, Up Conversion Nano Particles, Quantum Dots and Their
Applications 10.1007/978-981-10-1590-8_1

1. Exploration of New Phosphors
Using a Mineral-Inspired Approach
in Combination with Solution
Parallel Synthesis
Masato Kakihana1 , Hideki Kato1,
Makoto Kobayashi1, Yasushi Sato2,
Koji Tomita3 and Tetsufumi Komukai4
(1) Institute of Multidisciplinary Research for Advanced
Materials, Tohoku University, Sendai 980-8577, Japan
(2) Department of Chemistry, Faculty of Science, Okayama

University of Science, Okayama 700-0005, Japan
(3) Department of Chemistry, School of Science, Tokai
University, Hiratsuka 259-1292, Japan
(4) Ichikawa Research Center, Sumitomo Metal Mining Co.,
Ltd., Ichikawa, Japan

Masato Kakihana
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Email:
Abstract
We introduce the concept, as well as the methodology, of using a
mineral-inspired approach in combination with solution parallel
synthesis for the exploration of new phosphors. The key to
successful discovery of new phosphors is the construction of a
promising composition library. In this chapter, the construction of
an artificial composition library inspired by minerals is
proposed. By employing this approach, we have discovered
various new phosphors including NaAlSiO4:Eu2+,
BaZrSi3O9:Eu2+, Na3ScSi3O9:Eu2+, SrCaSiO4:Eu2+, and
Ca2SiO4:Eu2+ that emit green-yellow (553 nm), cyan blue-green
(480 nm), green (520 nm), orange-red (615 nm), and deep-red
(650 nm) light, respectively, when excited at 365–460 nm.
Among these phosphors, the most prominent result was the
observation of unusual deep-red emission from Ca2SiO4:Eu2+,
which originated from the phase transition from the normal phase to an

-phase when a sizable number of Ca2+ sites were


substituted by Eu2+ (up to 40 mol%). The reason for the
emergence of the deep-red emission of -Ca2SiO4:Eu2+ is
discussed in terms of “crystal site engineering.” In addition to
these silicate-based phosphors, exploration of new oxide upconversion phosphors was carried out using solution parallel
synthesis. Among various niobates and tantalates of rare earth
elements, Y0.5Yb0.4Er0.1Ta7O19 was discovered as a new oxide
up-conversion phosphor with a good internal quantum efficiency
(2.05 %) compared with those of previously known upwww.pdfgrip.com


conversion phosphors, which are typically below 1 %.

1.1 Introduction
One of the characteristic features of inorganic materials is that
they include almost all the elements in the periodic table. In other
words, the types of existing inorganic substances are enormous,
and countless unknown new inorganic substances may also exist.
We will focus on silicon, which has the second highest Clarke
number and is the second most abundant element on Earth after
oxygen. According to the database of inorganic compounds
(https:// icsd. fiz-karlsruhe. de/ ), among the inorganic materials
that include silicon, as of September 2014, there are 21,386 types
of inorganic substances with known crystal structures. Most of
these substances are mineral-derived. For example, (Ba,
Sr)2SiO4, which is a well-known host for phosphors, is also a
mineral-derived inorganic substance called orthosilicate. Many
functional inorganic substances are artificial substances that can
also achieve new functions or structures by forming solid
solutions. Solid solutions are substituted inorganic substances,
such as the new structure created by substituting the barium and

strontium of (Ba, Sr)2SiO4 with magnesium and calcium. By
including such solid solutions, the types of inorganic substances
increase from 21,386 to 100,000 or 1,000,000, etc., up to
astronomical numbers. It is impossible to comprehensively
synthesize such an abundance of inorganic substances, and
therefore, new materials and new functions are left unexplored in
the present situation.
In this chapter, we first briefly introduce the basis of (thin
film) combinatorial, melt combinatorial, combinatorial-based
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computing science, and solution parallel synthesis, which are
methods to search for new inorganic substances and inorganic
materials (Sect. 1.2). Next, we introduce the details with applied
examples of the “solution parallel synthesis method,” which the
authors’ group has developed (Sect. 1.3). In particular, it is noted
as a precaution that there are limits to the solution methods that
can be used for solution parallel synthesis. In Sect. 1.4, an actual
example of a search for new phosphors using the solution parallel
synthesis method guided by minerals is introduced as a new
approach to new material searches. In particular, the importance
of the selection of the lead compound, a key to the search, is
referred to in order to indicate that a material search can be
reasonably performed by using a mineral as a hint.
The solution parallel synthesis method can be deemed one of
the most effective methods of searching for phosphors, and
examples of new phosphors discovered using this method are
introduced. The application of the solution parallel synthesis
method to search for new dielectrics, battery materials,

photocatalysts, etc., indicates that there are still some problems to
be overcome, but we believe that it is useful for the researchers
concerned with new inorganic material searches to know the
solution parallel synthesis method.

1.2 Methods for Exploring New Inorganic
Substances and Materials
1.2.1 Combinatorial Approach
Thin film combinatorial is one of the ultrahigh-speed material
screening techniques, which was actively studied from the midwww.pdfgrip.com


1990s to the early 2000s, and laser molecular beam epitaxy
(MBE) and chemical vapor deposition (CVD) are used as
methods for forming thin films. In principle, tens of thousands of
types of thin films can be manufactured at a time, which is
effective for the exploration of new functions in ferroelectric thin
films [1, 2]. Figure 1.1 schematically shows the principle of thin
film combinatorial using laser MBE.

Fig. 1.1 Schematic illustration of the combinatorial synthesis of functional thin films

Within a vacuum chamber, the targeted materials (A, B, C,
etc.) are volatilized under high-power UV laser irradiation to
form the components of thin films laminated on a substrate. By
rotating the target as well as moving a shielding plate (i.e., mask)
in the x–y direction, a substance with the desired composition is
formed as a film on the substrate. The lower part of the substrate
is irradiated with another laser, such as an infrared laser, to
produce a temperature gradient, which allows determination of

the optimum film production temperature. This method has
resulted in brilliant achievements in the creation of new functions
by the formation of epitaxial films and artificial superlattices,
through the use of single-crystal substrates with ultraclean
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surfaces [1, 2].
In recent years, this technique has been extensively expanded
using combinatorial and high-throughput screening of materials to
search for a variety of new materials, including hydrogen storage
materials [3], Li-ion battery materials [4], Pd-based metal oxide
catalysts [5], and piezoelectric materials [6].

1.2.2 Melt Combinatorial
Melt combinatorial is a method to melt multiple oxide mixed
powders using an arc imaging furnace, which enables efficient
material searches. However, because melting makes it easy to
obtain glass substances and may induce evaporation of some
components, there are problems with the versatility of this
method. Melt combinatorial was developed as a new phosphor
exploration method by Professor Toda’s group at Niigata
University [7]. As a result of this approach, the group
successfully discovered a new red-emitting phosphate phosphor
caused by blue photoexcitation by activating Eu2+ in NaMgPO4
with an olivine-type structure. NaMgPO4 is a common phosphor
that usually has a glaserite-type structure, and the material in
which Eu2+ was activated has blue emission under ultraviolet
photoexcitation [8]. Phosphate is a kind of oxide, and red
emission under blue photoexcitation is very rare, except in

nitrides. Even when the temperature is elevated to 150 °C, this
phosphor, with good temperature quenching characteristics,
maintains about 80 % of the emission intensity compared with
that at room temperature. The exploration of new phosphors by
melt combinatorial will be accelerated in the future [7].
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1.2.3 Combinatorial by Computational
Science Algorithms
Combinatorial by computational science algorithms is a highly
effective method that enables a reasonable prediction of
composition optimization and can be applied to a search for
materials in conjunction with an experimental combinatorial
method. This method, developed by Professor Kee-Sun Sohn’s
group at Sejong University in South Korea, is especially effective
for the exploration of new phosphors. In recent years, the
combination of this method with experimental combinatorial
methods has been extended to the exploration of new oxynitride
phosphors [9–15].

1.2.4 Solution Parallel Synthesis Method
Figure 1.2 schematically shows the solution parallel synthesis
method [16–19]. Aqueous solutions are prepared containing
various concentrations of metal salts (A, B, C, D, E, etc.). In the
example shown in Fig. 1.2, the solution referred to as Eu is
prepared because europium ions are used as an activator. Also,
in this example, GMS (glycol-modified silane) [17] is used as a
silicon source, as the exploration of a new silicate-based
phosphor is simulated. In addition, citric acid is required to

stabilize the solution system; when using water as the solvent, the
solution method is the amorphous metal complex method,
whereas, when using glycol as the solvent, the solution method is
the polymerizable complex method [16, 20, 21]. Using the
“composition library” described later, a series of solution
samples are produced in vitro. The composition library is a set of
compositions corresponding to the sample series aimed at
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synthesis. The solution set of this series is chemically processed
at the same time to obtain gelation or polyester resins, and then
subjected to a series of heat treatments to perform the phosphor
synthesis of interest. Phosphor screening can be performed by
irradiating the completed set of phosphors with a portable lamp
to observe the emission by visual inspection. The picture in the
bottom left of Fig. 1.2 shows the emission of synthesized
phosphor samples when irradiated at 254, 365, and 400 nm. For
example, sample No. 3 is strongly yellow-green luminescent and
sample No. 7 is strongly green-white luminescent. Therefore, a
second cycle of solution parallel synthesis was implemented to
fine-tune the composition in the vicinity of these samples for the
purpose of identifying the composition of phosphors with stronger
emission intensities. This repetition leads to the discovery of new
phosphors.

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Fig. 1.2 Scheme of solution parallel synthesis for the exploration of new phosphors;

GMS (glycol-modified silane) was used as a convenient silicon source; visual
observation of emission under UV to near-UV irradiation [16]

Although the solution parallel synthesis method enables the
parallel synthesis of dozens of samples at a time, as evident in
Fig. 1.2, it requires extra time compared with the thin film
combinatorial and melt combinatorial approaches because it
involves multiple processes. However, the use of a highly
reliable solution method makes it possible to increase the
accuracy of each synthesis process, resulting in improved
reliability of the material search. In addition, the high versatility
of this method is a significant benefit. The details of the solution
parallel synthesis method are described in the next section.

1.3 Details of the Solution Parallel Synthesis
Method
1.3.1 Conditions Required for Solution
Parallel Synthesis
The solution parallel synthesis method we have developed is
applied to the efficient search for new materials, quick
determination of the optimum composition in the functional
materials, and realization of high functionalization [16, 18, 22,
23]. In order to accomplish this, the following conditions must be
met.
1. A solution method with excellent composition control for
ceramics should be applied.
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2. The parallel synthesis of substances with different

compositions should be possible using the same experimental
conditions, including reaction time.
3. Substances should be relatively insensitive to moisture in the
air.
The solution methods that meet these three conditions are
limited, and any one of those solution methods cannot always be
applied.
In Fig. 1.3, we select the solution methods available for
solution parallel synthesis in light of the above three
requirements. Depending on the type of metal ions in the solution,
the precipitation method [20] may or may not form a precipitate.
In addition, even if a precipitate is formed, the solubility varies
depending on the type of metal. Therefore, this method does not
meet Conditions 1 and 2. Thus, the precipitation method is
ineligible as a solution method for the solution parallel synthesis
method.

Fig. 1.3 Selection criteria of the solution method to incorporate in the solution parallel
synthesis method; Excellent composition control to ensure homogeneity, Able to
perform parallel synthesis under the same condition, Insensitive to humidity and able
to perform synthesis in air; : Excellent, : Good, : fair, ×: Poor
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Furthermore, the sol–gel method using an alkoxide [20] does
not meet Condition 2 because the hydrolysis rate or
polycondensation rate varies depending on the type of metal
alkoxide. In addition, many typical metal alkoxides are unstable
compounds and are affected by humidity in the atmosphere;
therefore, this method does not meet Condition 3. Thus, the sol–

gel method using an alkoxide is ineligible as a solution method
for the solution parallel synthesis method.
In the hydrothermal method [20, 21], depending on the type of
metal ions used, the rate of the chemical reaction in aqueous
solution under a given hydrothermal condition varies. Therefore,
this method does not meet Condition 2, and the hydrothermal
method also cannot be used as a solution method for the solution
parallel synthesis method.
On the other hand, because of its principle, the polymerizable
complex method [20, 21] has excellent composition control, and
without much attention to the type of metal, synthesis is possible
under the same conditions. Moreover, because this process can
be carried out in air, it is the most appropriate solution method
for the solution parallel synthesis method. Methods similar to the
polymerizable complex method, including the amorphous metal
complex (AMC) method [20] and the polyvinyl alcohol (PVA)
method [20, 21], can also be used as solution methods for the
solution parallel synthesis method.

1.3.2 Pictures of the Solution Parallel
Synthesis Method in Operation
To help understanding the readers, an actual phosphor search
using the solution parallel synthesis method with the
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polymerizable complex method as the solution method is
introduced in the photographs shown in Figs. 1.4, 1.5, and 1.6.

Fig. 1.4 Experimental view of the solution parallel synthesis method (part 1): a solution

preparation; b polymerization in a dry box; c polyester reaction; and d solidified polyester
resin

Fig. 1.5 Experimental view of the solution parallel synthesis method (part 2): resin
decomposition in a sand bath a at the start time and b after 30 min; c degreasing
product; and d calcination product at 500 °C

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Fig. 1.6 Experimental view of the solution parallel synthesis method (part 3): a
products after firing at 1200 °C and b products irradiated with ultraviolet light (254 nm)

First, 20 types of solutions with different metal composition
ratios are prepared in test tubes (construction of the composition
library), and citric acid and glycol are added to these test tubes
as gelling agents (Fig. 1.4a). Then, these 20 test tubes are placed
in an oven and heated at 120 °C to concentrate the solution and
promote polymerization (Fig. 1.4b). The polymerizable complex
method [20, 21] is a solution method, in which the polyester
reaction between citric acid and glycol is allowed to proceed,
and as a result, metal ions or metal–citric acid complexes are
uniformly trapped in a polyester resin. The polyester reaction is a
dehydration reaction; extensive bubbling occurs during the
release of water from the highly viscous polyester resin, as
shown in Fig. 1.4c. To prevent the overflow of these bubbles, tall
test tubes are used as the reaction containers. Figure 1.4d shows
one of the test tubes turns upside down after the reaction, and the
solidified polyester resin can be observed. The polyester resins
are inserted into a sand bath at 300 °C to decompose the resins

(Fig. 1.5a). The decomposition of the resins generates steam
(Fig. 1.5b). Figure 1.5c shows the products after degreasing.
Figure 1.5d shows the products obtained by putting the degreased
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products into crucibles and applying heat treatment in an electric
furnace at 500 °C. Further heat treatment in an electric furnace at
1200 °C forms the fluorescent substances, i.e., “phosphors.”
Figure 1.6a shows the calcination products obtained after the
treatment at 1200 °C. Figure 1.6b shows the emission from the
resulting 20 samples when irradiated with ultraviolet light
(254 nm) using a portable UV lamp. This enables visual
confirmation of the substances that show strong blue, green, or
red depending on the composition and the substances with no
emission. A substance with strong light emission is then selected,
a new composition library in the vicinity of its composition is
constructed, and the solution parallel synthesis process is
repeated to determine the optimum composition.

1.4 Exploration of New Phosphors Inspired
by Minerals Using the Solution Parallel
Synthesis Method
In contrast to the continual discovery of new organic compounds,
new inorganic substances have not been discovered frequently. In
the field of drug discovery, useful antibiotics are developed
daily, so why is the development rate of new inorganic substance
slow?
One reason for this is derived from the different essential
principles of inorganic and organic synthesis. For inorganic

synthesis reactions, slow diffusion of metal ions in solids is ratelimiting, whereas organic synthesis reactions are generally based
on reactions between molecules. For this reason, it is thought that
the efficiency of the exploration of inorganic substances is quite
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low, and the opportunity to discover new substance is reduced
correspondingly. In addition to the difficulties associated with the
synthesis itself, we think the selection of an appropriate lead
substance, which is the starting point for exploration, is also a
problem.
A lead substance is the substance from which the library for
substance exploration is constructed. In the field of drug
discovery, the lead substance is either a natural compound or a
synthetic substance. Specifically, a synthetic substance is selected
as a lead compound, and the required functional groups are
introduced, for example, to construct a library consisting of a set
of modifiers for combinatorial synthesis. It is possible to
determine whether the modifiers can exist from the standpoint of
organic synthetic chemistry. That is, it is possible to conduct
substance exploration rationally, rather than by random
combinatorial synthesis. On the other hand, with inorganic
substances, it is difficult to predict whether the corresponding
substances can exist for any composition. From the standpoint of
crystal chemistry, a certain degree of prediction is possible, but,
in many cases, it is difficult to be conclusive unless the actual
synthesis is attempted. For this reason, the exploration of
inorganic substances using a combinatorial method is likely to
rely on exhaustive synthesis with no basis and, at this time, is far
from rational. The fact that the number of new substance

discoveries is limited, even when a combinatorial method with
the advantage of concurrent synthesis of substances with tens or
hundreds of thousands of compositions is used, may indicate the
selection of inappropriate lead substances. That is, we think the
answer to the question “Why are new inorganic substances not
discovered frequently?” could be “There were problems
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selecting the lead substance.”
We proposed to seek a lead substance for exploration of new
inorganic substance in natural minerals. That is, exploration of
new inorganic substances inspired by minerals using the solution
parallel synthesis method. In this section, we introduce examples
of the exploration of new phosphors based on this strategy.

1.4.1 Practical Exploration of Novel
Phosphors Using a Mineral-Inspired Method
with Solution Parallel Synthesis
Figure 1.7 shows a flowchart for the exploration of novel
phosphors using a mineral-inspired method with solution parallel
synthesis.

Fig. 1.7 Scheme of the search for novel phosphors inspired by minerals using the
solution parallel synthesis method [23]

First, a mineral database provided by the International
Mineralogical Association (IMA, http:// www. ima-mineralogy.
org/ ), Mindat (http:// www. mindat. org/ ), etc. is accessed.
Data on up to tens of thousands of kinds of basic minerals are

available, so a search can be conducted by category, such as
silicates, phosphates, and borates. Next, model minerals (lead
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substances) are selected, and a large-scale task of grouping is
conducted. There are several possible ways of grouping. One is
to group the minerals based on the characteristics of their crystal
chemical structure. For example, in mineralogy, silicate minerals
are classified into groups such as nesosilicates, sorosilicates,
inosilicates, cyclosilicates, and phyllosilicates, as shown in
Fig. 1.8, based on the way the silicate ion, which is the
fundamental building unit of these structures, is bound. Therefore,
using this method, minerals belonging to each group are selected
as lead substances to construct a library. Another method is to
group the minerals by the element group. Here, we will describe
this second method, using silicates as an example.

Fig. 1.8 A variety of silicates composed of [SiO4]4− as a fundamental structural unit
and the various binding modes of [SiO4]4− [23]

Figure 1.9 shows silicates classified into nine categories by
elemental composition. Library 1 consists mainly of calcium
silicate or magnesium silicate minerals, Library 2 of calcium–
magnesium silicate minerals, Library 3 of calcium–aluminum
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