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In [[condensed matter physics]] and [[materials science]], an '''amorphous solid''' (or '''non-crystalline solid''') is a [[solid]] that lacks the [[long-range order]] that is a characteristic of a [[crystal]]. The terms "[[glass]]" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a [[glass transition]].<ref name=":6">{{ | In [[condensed matter physics]] and [[materials science]], an '''amorphous solid''' (or '''non-crystalline solid''') is a [[solid]] that lacks the [[long-range order]] that is a characteristic of a [[crystal]]. The terms "[[glass]]" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a [[glass transition]].<ref name=":6">{{cite book |last1=Elliott |first1=S. R. |title=Properties and Applications of Amorphous Materials |chapter=The Structure of Amorphous Materials |date=2001 |pages=1–11 |doi=10.1007/978-94-010-0914-0_1 |isbn=978-0-7923-6811-3 }}</ref> Examples of amorphous solids include glasses, [[metallic glasses]], and certain types of [[plastic]]s and [[polymer]]s.<ref>{{cite journal |last1=Ponçot |first1=M. |last2=Addiego |first2=F. |last3=Dahoun |first3=A. |title=True intrinsic mechanical behaviour of semi-crystalline and amorphous polymers: Influences of volume deformation and cavities shape |journal=International Journal of Plasticity |date=January 2013 |volume=40 |pages=126–139 |doi=10.1016/j.ijplas.2012.07.007 |url=https://hal.science/hal-01296898 }}</ref><ref name=":Z">{{Cite book |last1=Zaccone |first1=A. |title=Theory of Disordered Solids |series=Lecture Notes in Physics |publisher=Springer |year=2023 |pages=18–33 |volume=1015 |doi=10.1007/978-3-031-24706-4 |isbn=978-3-031-24705-7 }}</ref> | ||
== Etymology == | == Etymology == | ||
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== Structure == | == Structure == | ||
[[File:Crystalline vs. Amorphous solid.png|thumb|Crystalline vs. amorphous solid]] | [[File:Crystalline vs. Amorphous solid.png|thumb|Crystalline vs. amorphous solid]] | ||
Amorphous materials have an internal structure of molecular-scale structural blocks that can be similar to the basic structural units in the crystalline phase of the same compound.<ref>{{cite journal | first1 = Juraj| last1 = Mavračić| first2 = Felix C.| last2 = Mocanu| first3 = Volker L.| last3 = Deringer| first4 = Gábor| last4 = Csányi| first5 = Stephen R.| last5 = Elliott| title = Similarity Between Amorphous and Crystalline Phases: The Case of TiO<sub>2</sub>|journal = [[J. Phys. Chem. Lett.]]| volume = 9| issue = 11| pages = 2985–2990| year = 2018| doi = 10.1021/acs.jpclett.8b01067| pmid = 29763315| url = https://www.repository.cam.ac.uk/handle/1810/283145| doi-access = free}}</ref> Unlike in crystalline materials, however, no long-range regularity exists: amorphous materials cannot be described by the repetition of a finite unit cell. Statistical measures, such as the atomic density function and [[radial distribution function]], are more useful in describing the structure of amorphous solids.<ref name=":6" /><ref name=":Z" /> | Amorphous materials have an internal structure of molecular-scale structural blocks that can be similar to the basic structural units in the crystalline phase of the same compound.<ref>{{cite journal | first1 = Juraj| last1 = Mavračić| first2 = Felix C.| last2 = Mocanu| first3 = Volker L.| last3 = Deringer| first4 = Gábor| last4 = Csányi| first5 = Stephen R.| last5 = Elliott| title = Similarity Between Amorphous and Crystalline Phases: The Case of TiO<sub>2</sub>|journal = [[J. Phys. Chem. Lett.]]| volume = 9| issue = 11| pages = 2985–2990| year = 2018| doi = 10.1021/acs.jpclett.8b01067| pmid = 29763315| bibcode = 2018JPCL....9.2985M| url = https://www.repository.cam.ac.uk/handle/1810/283145| doi-access = free}}</ref> Unlike in crystalline materials, however, no long-range regularity exists: amorphous materials cannot be described by the repetition of a finite [[unit cell]]. Statistical measures, such as the atomic density function and [[radial distribution function]], are more useful in describing the structure of amorphous solids.<ref name=":6" /><ref name=":Z" /> | ||
[[File:Lake Mjøsa sunrise reflected in window 01.jpg|thumb|upright|[[Glass]] is a commonly encountered example of amorphous solids.]] | [[File:Lake Mjøsa sunrise reflected in window 01.jpg|thumb|upright|[[Glass]] is a commonly encountered example of amorphous solids.]] | ||
Although amorphous materials lack long range order, they exhibit localized order on small length scales.<ref name=":6" /> By convention, ''short range order'' extends only to the nearest neighbor shell, typically only 1-2 atomic spacings.<ref name=":0">{{ | Although amorphous materials lack long range order, they exhibit localized order on small length scales.<ref name=":6" /> By convention, ''short range order'' extends only to the nearest neighbor shell, typically only 1-2 [[atomic spacing|atomic spacings]].<ref name=":0">{{cite journal |last1=Cheng |first1=Y.Q. |last2=Ma |first2=E. |title=Atomic-level structure and structure–property relationship in metallic glasses |journal=Progress in Materials Science |date=May 2011 |volume=56 |issue=4 |pages=379–473 |doi=10.1016/j.pmatsci.2010.12.002 }}</ref> ''Medium range order'' may extend beyond the short range order by 1-2 nm.<ref name=":0" /> | ||
== Fundamental properties of amorphous solids == | == Fundamental properties of amorphous solids == | ||
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Although there are various theoretical models, neither [[glass transition]] nor low-temperature properties of [[glassy solids]] are well understood on the [[fundamental physics]] level. | Although there are various theoretical models, neither [[glass transition]] nor low-temperature properties of [[glassy solids]] are well understood on the [[fundamental physics]] level. | ||
Amorphous solids is an important area of [[condensed matter physics]] aiming to understand these substances at high temperatures of [[glass transition]] and at low [[temperature]]s towards [[absolute zero]]. From the 1970s, low-temperature properties of amorphous solids were studied experimentally in great detail.<ref name="Stephens2021">{{Cite book |last1=Stephens |first1=Robert B. |first2=Xiao |last2=Liu |title=Low-Energy Excitations in Disordered Solids. A Story of the 'Universal' Phenomena of Structural Tunneling |year=2021 |doi=10.1142/11746|isbn=978-981-12-1724-1 | | Amorphous solids is an important area of [[condensed matter physics]] aiming to understand these substances at high temperatures of [[glass transition]] and at low [[temperature]]s towards [[absolute zero]]. From the 1970s, low-temperature properties of amorphous solids were studied experimentally in great detail.<ref name="Stephens2021">{{Cite book |last1=Stephens |first1=Robert B. |first2=Xiao |last2=Liu |title=Low-Energy Excitations in Disordered Solids. A Story of the 'Universal' Phenomena of Structural Tunneling |year=2021 |doi=10.1142/11746 |isbn=978-981-12-1724-1 }}{{pn|date=September 2025}}</ref><ref name="Ramos2022">{{Cite book |editor-last1=Ramos |editor-first1=M. |title=Low-Temperature Thermal and Vibrational Properties of Disordered Solids. A Half-Century of Universal 'Anomalies' of Glasses |year=2022 |doi=10.1142/q0371 |arxiv=2010.02851 |isbn=978-1-80061-257-0 |last1=Grushin |first1=Adolfo G. }}{{pn|date=September 2025}}</ref> For all of these substances, [[specific heat]] has a (nearly) linear dependence as a function of temperature, and [[thermal conductivity]] has nearly quadratic temperature dependence. These properties are conventionally called '''anomalous''' being very different from properties of [[crystalline solid]]s. | ||
On the phenomenological level, many of these properties were described by a collection of tunnelling two-level systems.<ref name="AHV1972">{{Cite journal |last1=Anderson |first1=P.W. |last2=Halperin |first2=B.I. |last3=Varma |first3=C.M |title=Anomalous low-temperature thermal properties of glasses and spin glasses |year=1972 |journal=Philosophical Magazine|volume=25 |issue=1 |pages=1–9|doi=10.1080/14786437208229210|bibcode=1972PMag...25....1A }}</ref><ref name="Phillips1972">{{Cite journal |last1=Phillips |first1=W.A. |title= Tunneling states in amorphous solids |year=1972 |journal=J. Low Temp. Phys., Pp 751 |volume=7 |issue=3–4 |pages=351–360 |doi=10.1007/BF00660072|bibcode=1972JLTP....7..351P | | On the phenomenological level, many of these properties were described by a collection of tunnelling two-level systems.<ref name="AHV1972">{{Cite journal |last1=Anderson |first1=P.W. |last2=Halperin |first2=B.I. |last3=Varma |first3=C.M |title=Anomalous low-temperature thermal properties of glasses and spin glasses |year=1972 |journal=Philosophical Magazine |volume=25 |issue=1 |pages=1–9|doi=10.1080/14786437208229210 |bibcode=1972PMag...25....1A }}</ref><ref name="Phillips1972">{{Cite journal |last1=Phillips |first1=W.A. |title=Tunneling states in amorphous solids |year=1972 |journal=J. Low Temp. Phys., Pp 751 |volume=7 |issue=3–4 |pages=351–360 |doi=10.1007/BF00660072 |bibcode=1972JLTP....7..351P }}{{pn|date=September 2025}}</ref> Nevertheless, the microscopic theory of these properties is still missing after more than 50 years of the research.<ref name="Esquinazi1998">{{Cite book |editor-last1=Esquinazi |editor-first1=Pablo |title=Tunneling Systems in Amorphous and Crystalline Solids |year=1998 |doi=10.1007/978-3-662-03695-2 |isbn=978-3-642-08371-6 }}{{pn|date=September 2025}}</ref> | ||
Remarkably, a '''dimensionless''' quantity of internal friction is nearly universal in these materials.<ref name="Pohl2002">{{Cite journal |last1=Pohl |first1=R.O. |last2=etc |first2=etc |title=Low-temperature thermal conductivity and acoustic attenuation in amorphous solids |year=2002 |journal=Revs. Mod Phys. |volume=74 |issue=1 | | Remarkably, a '''dimensionless''' quantity of internal friction is nearly universal in these materials.<ref name="Pohl2002">{{Cite journal |last1=Pohl |first1=R.O. |last2=etc |first2=etc |title=Low-temperature thermal conductivity and acoustic attenuation in amorphous solids |year=2002 |journal=Revs. Mod Phys. |volume=74 |issue=1 |page=991|doi=10.1080/14786437208229210|bibcode=1972PMag...25....1A }}</ref> This quantity is a dimensionless ratio (up to a numerical constant) of the phonon [[wavelength]] to the phonon [[mean free path]]. Since the theory of tunnelling two-level states (TLSs) does not address the origin of the density of TLSs, this theory cannot explain the universality of internal friction, which in turn is proportional to the density of scattering TLSs. The theoretical significance of this important and unsolved problem was highlighted by [[Anthony Leggett]].<ref name="Leggett1991">{{Cite journal |last1=Leggett |first1=A.J. |title=Amorphous materials at low temperatures: why are they so similar?|year=1991 |journal=Physica B |volume=169 |issue=1–4 |pages=322–327 |doi=10.1016/0921-4526(91)90246-B|bibcode=1991PhyB..169..322L }}</ref> | ||
== Nano-structured materials == | == Nano-structured materials == | ||
Amorphous materials will have some degree of [[short-range order]] at the atomic-length scale due to the nature of intermolecular [[chemical bond]]ing.{{efn|See the [[structure of liquids and glasses]] for more information on non-crystalline material structure.}} Furthermore, in very small [[crystal]]s, short-range order encompasses a large fraction of the [[atom]]s; nevertheless, relaxation at the surface, along with interfacial effects, distorts the atomic positions and decreases structural order. Even the most advanced structural characterization techniques, such as [[X-ray diffraction]] and [[transmission electron microscopy]], can have difficulty distinguishing amorphous and crystalline structures at short-size scales.<ref>{{cite book | last1=Goldstein |first1=Joseph I. |last2=Newbury |first2=Dale E. |last3=Michael |first3=Joseph R. |last4=Ritchie |first4=Nicholas W. M. |last5=Scott |first5=John Henry J. |last6=Joy |first6=David C. |title=Scanning Electron Microscopy and X-ray Microanalysis |date=2018 |location=New York, NY |isbn=978- | Amorphous materials will have some degree of [[short-range order]] at the atomic-length scale due to the nature of intermolecular [[chemical bond]]ing.{{efn|See the [[structure of liquids and glasses]] for more information on non-crystalline material structure.}} Furthermore, in very small [[crystal]]s, short-range order encompasses a large fraction of the [[atom]]s; nevertheless, relaxation at the surface, along with interfacial effects, distorts the atomic positions and decreases structural order. Even the most advanced structural characterization techniques, such as [[X-ray diffraction]] and [[transmission electron microscopy]], can have difficulty distinguishing amorphous and crystalline structures at short-size scales.<ref>{{cite book | last1=Goldstein |first1=Joseph I. |last2=Newbury |first2=Dale E. |last3=Michael |first3=Joseph R. |last4=Ritchie |first4=Nicholas W. M. |last5=Scott |first5=John Henry J. |last6=Joy |first6=David C. |title=Scanning Electron Microscopy and X-ray Microanalysis |date=2018 |location=New York, NY |isbn=978-1-4939-6674-5 |edition=Fourth}}</ref> | ||
== Characterization of amorphous solids == | == Characterization of amorphous solids == | ||
Due to the lack of long-range order, standard crystallographic techniques are often inadequate in determining the structure of amorphous solids.<ref name=":1">{{ | Due to the lack of long-range order, standard crystallographic techniques are often inadequate in determining the structure of amorphous solids.<ref name=":1">{{cite journal |last1=Yang |first1=Yao |last2=Zhou |first2=Jihan |last3=Zhu |first3=Fan |last4=Yuan |first4=Yakun |last5=Chang |first5=Dillan J. |last6=Kim |first6=Dennis S. |last7=Pham |first7=Minh |last8=Rana |first8=Arjun |last9=Tian |first9=Xuezeng |last10=Yao |first10=Yonggang |last11=Osher |first11=Stanley J. |last12=Schmid |first12=Andreas K. |last13=Hu |first13=Liangbing |last14=Ercius |first14=Peter |last15=Miao |first15=Jianwei |title=Determining the three-dimensional atomic structure of an amorphous solid |journal=Nature |date=April 2021 |volume=592 |issue=7852 |pages=60–64 |doi=10.1038/s41586-021-03354-0 |pmid=33790443 |arxiv=2004.02266 |bibcode=2021Natur.592...60Y }}</ref> A variety of electron, X-ray, and computation-based techniques have been used to characterize amorphous materials. Multi-modal analysis is very common for amorphous materials.{{fact|date=September 2025}} | ||
=== X-ray and neutron diffraction === | === X-ray and neutron diffraction === | ||
Unlike crystalline materials, which exhibit strong [[Bragg's law|Bragg]] diffraction, the diffraction patterns of amorphous materials are characterized by broad and diffuse peaks.<ref name=":2">{{Cite journal |last=Billinge |first=Simon J. L. |date=2019-06-17 |title=The rise of the X-ray atomic pair distribution function method: a series of fortunate events |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |volume=377 |issue=2147 | | Unlike crystalline materials, which exhibit strong [[Bragg's law|Bragg]] diffraction, the diffraction patterns of amorphous materials are characterized by broad and diffuse peaks.<ref name=":2">{{Cite journal |last=Billinge |first=Simon J. L. |date=2019-06-17 |title=The rise of the X-ray atomic pair distribution function method: a series of fortunate events |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |volume=377 |issue=2147 |article-number=20180413 |doi=10.1098/rsta.2018.0413 |pmc=6501893 |pmid=31030657 |bibcode=2019RSPTA.37780413B }}</ref> As a result, detailed analysis and complementary techniques are required to extract real space structural information from the diffraction patterns of amorphous materials. It is useful to obtain diffraction data from both X-ray and neutron sources as they have different scattering properties and provide complementary data.<ref>{{Cite journal |last1=Ren |first1=Yang |last2=Zuo |first2=Xiaobing |date=2018-06-13 |title=Synchrotron X-Ray and Neutron Diffraction, Total Scattering, and Small-Angle Scattering Techniques for Rechargeable Battery Research |journal=Small Methods |volume=2 |issue=8 |article-number=1800064 |doi=10.1002/smtd.201800064 |osti=1558997 |doi-access=free }}</ref> [[Pair distribution function]] analysis can be performed on diffraction data to determine the probability of finding a pair of atoms separated by a certain distance.<ref name=":2" /> Another type of analysis that is done with diffraction data of amorphous materials is radial distribution function analysis, which measures the number of atoms found at varying radial distances away from an arbitrary reference atom.<ref>{{Cite journal |last1=Senjaya |first1=Deriyan |last2=Supardi |first2=Adri |last3=Zaidan |first3=Andi |date=2020-12-09 |title=Theoretical formulation of amorphous radial distribution function based on wavelet transformation |journal=AIP Conference Proceedings |volume=2314 |issue=1 |page=020001 |doi=10.1063/5.0034410 |bibcode=2020AIPC.2314b0001S |doi-access=free }}</ref> From these techniques, the local order of an amorphous material can be elucidated. | ||
=== X-ray absorption fine-structure spectroscopy === | === X-ray absorption fine-structure spectroscopy === | ||
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=== Atomic electron tomography === | === Atomic electron tomography === | ||
The atomic electron [[tomography]] technique is performed in transmission electron microscopes capable of reaching sub-Angstrom resolution. A collection of 2D images taken at numerous different tilt angles is acquired from the sample in question and then used to reconstruct a 3D image.<ref name=":3">{{ | The atomic electron [[tomography]] technique is performed in transmission electron microscopes capable of reaching sub-[[Angstrom]] resolution. A collection of 2D images taken at numerous different tilt angles is acquired from the sample in question and then used to reconstruct a 3D image.<ref name=":3">{{cite journal |last1=Zhou |first1=Jihan |last2=Yang |first2=Yongsoo |last3=Ercius |first3=Peter |last4=Miao |first4=Jianwei |title=Atomic electron tomography in three and four dimensions |journal=MRS Bulletin |date=April 2020 |volume=45 |issue=4 |pages=290–297 |doi=10.1557/mrs.2020.88 |bibcode=2020MRSBu..45..290Z }}</ref> After image acquisition, a significant amount of processing must be done to correct for issues such as drift, noise, and scan distortion.<ref name=":3" /> High-quality analysis and processing using atomic electron tomography results in a 3D reconstruction of an amorphous material detailing the atomic positions of the different species that are present. | ||
=== Fluctuation electron microscopy === | === Fluctuation electron microscopy === | ||
[[Fluctuation electron microscopy]] is another transmission electron microscopy-based technique that is sensitive to the medium-range order of amorphous materials. Structural fluctuations arising from different forms of medium-range order can be detected with this method.<ref name=":4">{{ | [[Fluctuation electron microscopy]] is another transmission electron microscopy-based technique that is sensitive to the medium-range order of amorphous materials. Structural fluctuations arising from different forms of medium-range order can be detected with this method.<ref name=":4">{{cite book |last1=Voyles |first1=Paul |last2=Hwang |first2=Jinwoo |title=Characterization of Materials |chapter=Fluctuation Electron Microscopy |date=2012 |pages=1–7 |doi=10.1002/0471266965.com138 |isbn=978-0-471-26882-6 }}</ref> Fluctuation electron microscopy experiments can be done in conventional or [[scanning transmission electron microscopy|scanning transmission electron microscope]] mode.<ref name=":4" /> | ||
=== Computational techniques === | === Computational techniques === | ||
Simulation and modeling techniques are often combined with experimental methods to characterize structures of amorphous materials. Commonly used computational techniques include [[density functional theory]], [[molecular dynamics]], and [[ | Simulation and modeling techniques are often combined with experimental methods to characterize structures of amorphous materials. Commonly used computational techniques include [[density functional theory]], [[molecular dynamics]], and [[reverse Monte Carlo]].<ref name=":1" /> | ||
== Uses and observations == | == Uses and observations == | ||
=== Amorphous thin films === | === Amorphous thin films === | ||
Amorphous phases are important constituents of [[thin film]]s. Thin films are solid layers of a few [[nanometre]]s to tens of [[micrometre]]s thickness that are deposited onto a substrate. So-called structure zone models were developed to describe the microstructure of thin films as a function of the [[homologous temperature]] (''T<sub>h</sub>''), which is the ratio of deposition temperature to melting temperature.<ref name="MoDe1969">{{cite | Amorphous phases are important constituents of [[thin film]]s. Thin films are solid layers of a few [[nanometre]]s to tens of [[micrometre]]s thickness that are deposited onto a substrate. So-called structure zone models were developed to describe the microstructure of thin films as a function of the [[homologous temperature]] (''T<sub>h</sub>''), which is the ratio of deposition temperature to melting temperature.<ref name="MoDe1969">{{cite report |first1=А.В. |last1=Демчишин |first2=Л.Д. |last2=Кулак |first3=В.А. |last3=Явор |title=Структура и механические свойства толстых металлических конденсатов, упрочненных дисперсными частицами различного типа |trans-title=Structure and mechanical properties of thick metal condensates reinforced with dispersed particles of various types |url=https://www.researchgate.net/publication/313053359 }}{{rs|date=September 2025}}</ref><ref name="Thor1974">{{citation | first = John A.| last = Thornton| title = Influence of Apparatus Geometry and Deposition Conditions on the Structure and Topography of Thick Sputtered Coatings| journal = [[Journal of Vacuum Science and Technology]]| volume = 11| issue = 4| pages = 666–670| year = 1974| doi = 10.1116/1.1312732| bibcode = 1974JVST...11..666T}}</ref> According to these models, a necessary condition for the occurrence of amorphous phases is that (''T<sub>h</sub>'') has to be smaller than 0.3. The deposition temperature must be below 30% of the melting temperature.{{efn|For higher values, the surface diffusion of deposited atomic species would allow for the formation of crystallites with long-range atomic order.}}{{Citation needed|date=September 2022}} | ||
=== Superconductivity === | === Superconductivity === | ||
[[File:Bulk Metallic Glass Sample.jpg|thumb|upright|[[Amorphous metal]]s have low [[toughness]], but high strength]] | [[File:Bulk Metallic Glass Sample.jpg|thumb|upright|[[Amorphous metal]]s have low [[toughness]], but high strength]] | ||
Regarding their applications, amorphous metallic layers played an important role in the discovery of [[superconductivity]] in [[amorphous metal]]s made by Buckel and Hilsch.<ref name="Buck1956">{{cite journal | first1 = W.| | Regarding their applications, amorphous metallic layers played an important role in the discovery of [[superconductivity]] in [[amorphous metal]]s made by Buckel and Hilsch.<ref name="Buck1956">{{cite journal |last1=Buckel |first1=W. |last2=Hilsch |first2=R. |title=Supraleitung und elektrischer Widerstand neuartiger Zinn-Wismut-Legierungen |journal=Zeitschrift für Physik |date=February 1956 |volume=146 |issue=1 |pages=27–38 |doi=10.1007/BF01326000 |bibcode=1956ZPhy..146...27B }}</ref><ref name="Buck1961">{{cite conference|last=Buckel|first=W.|title=The influence of crystal bonds on film growth|book-title=Elektrische en Magnetische Eigenschappen van dunne Metallaagies|place=Leuven, Belgium|date=1961}}</ref> The superconductivity of amorphous metals, including amorphous metallic thin films, is now understood to be due to [[phonon]]-mediated [[Cooper pair]]ing. The role of [[structural disorder]] can be rationalized based on the strong-coupling [[Eliashberg theory]] of superconductivity.<ref name="Baggioli">{{cite journal |last1=Baggioli |first1=Matteo |last2=Setty |first2=Chandan |last3=Zaccone |first3=Alessio |title=Effective theory of superconductivity in strongly coupled amorphous materials |journal=Physical Review B |date=3 June 2020 |volume=101 |issue=21 |article-number=214502 |doi=10.1103/PhysRevB.101.214502 |arxiv=2001.00404 |bibcode=2020PhRvB.101u4502B |hdl=10486/703598 }}</ref> | ||
=== Thermal protection === | === Thermal protection === | ||
Amorphous solids typically exhibit higher localization of heat carriers compared to crystalline, giving rise to low thermal conductivity.<ref name=":5">{{ | Amorphous solids typically exhibit higher localization of heat carriers compared to crystalline, giving rise to low thermal conductivity.<ref name=":5">{{cite journal |last1=Zhou |first1=Wu-Xing |last2=Cheng |first2=Yuan |last3=Chen |first3=Ke-Qiu |last4=Xie |first4=Guofeng |last5=Wang |first5=Tian |last6=Zhang |first6=Gang |title=Thermal Conductivity of Amorphous Materials |journal=Advanced Functional Materials |date=2020 |volume=30 |issue=8 |article-number=1903829 |doi=10.1002/adfm.201903829 }}</ref> Products for thermal protection, such as [[thermal barrier]] coatings and insulation, rely on materials with ultralow thermal conductivity.<ref name=":5" /> | ||
=== Technological uses === | === Technological uses === | ||
Today, [[optical coating]]s made from [[Titanium dioxide|TiO<sub>2</sub>]], [[Silicon dioxide|SiO<sub>2</sub>]], [[Tantalum pentoxide|Ta<sub>2</sub>O<sub>5</sub>]] etc. (and combinations of these) in most cases consist of amorphous phases of these compounds. Much research is carried out into thin amorphous films as a gas-separating [[Biological membrane|membrane]] layer.<ref name="Vos1998">{{cite journal|first1 = Renate M.|last1 = de Vos|first2 = Henk|last2 = Verweij|title = High-Selectivity, High-Flux Silica Membranes for Gas Separation|journal = [[Science (journal)|Science]]|volume = 279|issue = 5357|pages = 1710–1711|year = 1998|pmid = 9497287|doi = 10.1126/science.279.5357.1710|bibcode = 1998Sci...279.1710D}}</ref> The technologically most important thin amorphous film is probably represented by a few nm thin SiO<sub>2</sub> layers serving as isolator above the conducting channel of a [[MOSFET|metal-oxide semiconductor field-effect transistor]] (MOSFET). Also, [[amorphous silicon|hydrogenated amorphous silicon]] (Si:H) is of technical significance for [[thin-film solar cells]].{{efn|In the case of hydrogenated amorphous silicon, the missing long-range order between silicon atoms is partly induced by the presence of hydrogen in the per cent range.}} | Today, [[optical coating]]s made from [[Titanium dioxide|TiO<sub>2</sub>]], [[Silicon dioxide|SiO<sub>2</sub>]], [[Tantalum pentoxide|Ta<sub>2</sub>O<sub>5</sub>]] etc. (and combinations of these) in most cases consist of amorphous phases of these compounds. Much research is carried out into thin amorphous films as a gas-separating [[Biological membrane|membrane]] layer.<ref name="Vos1998">{{cite journal|first1 = Renate M.|last1 = de Vos|first2 = Henk|last2 = Verweij|title = High-Selectivity, High-Flux Silica Membranes for Gas Separation|journal = [[Science (journal)|Science]]|volume = 279|issue = 5357|pages = 1710–1711|year = 1998|pmid = 9497287|doi = 10.1126/science.279.5357.1710|bibcode = 1998Sci...279.1710D}}</ref> The technologically most important thin amorphous film is probably represented by a few nm thin SiO<sub>2</sub> layers serving as isolator above the conducting channel of a [[MOSFET|metal-oxide semiconductor field-effect transistor]] (MOSFET). Also, [[amorphous silicon|hydrogenated amorphous silicon]] (Si:H) is of technical significance for [[thin-film solar cells]].{{efn|In the case of hydrogenated amorphous silicon, the missing long-range order between silicon atoms is partly induced by the presence of hydrogen in the per cent range.}}{{fact|date=September 2025}} | ||
=== Pharmaceutical use === | === Pharmaceutical use === | ||
In the [[pharmaceutical industry]], some amorphous drugs have been shown to offer higher [[bioavailability]] than their crystalline counterparts as a result of the higher [[solubility]] of the amorphous phase. However, certain compounds can undergo [[Precipitation (chemistry)| precipitation]] in their amorphous form ''[[In vivo supersaturation|in vivo]]'' and can then decrease mutual bioavailability if administered together.<ref>{{ | In the [[pharmaceutical industry]], some amorphous drugs have been shown to offer higher [[Bioavailability (medicine)|bioavailability]] than their crystalline counterparts as a result of the higher [[solubility]] of the amorphous phase. However, certain compounds can undergo [[Precipitation (chemistry)| precipitation]] in their amorphous form ''[[In vivo supersaturation|in vivo]]'' and can then decrease mutual bioavailability if administered together.<ref>{{cite journal |last1=Hsieh |first1=Yi-Ling |last2=Ilevbare |first2=Grace A. |last3=Van Eerdenbrugh |first3=Bernard |last4=Box |first4=Karl J. |last5=Sanchez-Felix |first5=Manuel Vincente |last6=Taylor |first6=Lynne S. |title=pH-Induced Precipitation Behavior of Weakly Basic Compounds: Determination of Extent and Duration of Supersaturation Using Potentiometric Titration and Correlation to Solid State Properties |journal=Pharmaceutical Research |date=October 2012 |volume=29 |issue=10 |pages=2738–2753 |doi=10.1007/s11095-012-0759-8 |pmid=22580905 }}</ref><ref>{{Cite journal |last1=Dengale |first1=Swapnil Jayant |last2=Grohganz |first2=Holger |last3=Rades |first3=Thomas |last4=Löbmann |first4=Korbinian |date=May 2016 |title=Recent Advances in Co-amorphous Drug Formulations |journal=Advanced Drug Delivery Reviews |volume=100 |pages=116–125 |doi=10.1016/j.addr.2015.12.009 |pmid=26805787 }}</ref> Studies of GDC-0810 ASDs show a strong interrelationship between microstructure, physical properties and dissolution performance.<ref>{{cite journal |last1=Jia |first1=Wei |last2=Yawman |first2=Phillip D. |last3=Pandya |first3=Keyur M. |last4=Sluga |first4=Kellie |last5=Ng |first5=Tania |last6=Kou |first6=Dawen |last7=Nagapudi |first7=Karthik |last8=Luner |first8=Paul E. |last9=Zhu |first9=Aiden |last10=Zhang |first10=Shawn |last11=Hou |first11=Hao Helen |title=Assessing the Interrelationship of Microstructure, Properties, Drug Release Performance, and Preparation Process for Amorphous Solid Dispersions Via Noninvasive Imaging Analytics and Material Characterization |journal=Pharmaceutical Research |date=December 2022 |volume=39 |issue=12 |pages=3137–3154 |doi=10.1007/s11095-022-03308-9 |pmid=35661085 }}</ref> | ||
=== In soils === | === In soils === | ||
| Line 70: | Line 70: | ||
== Phase == | == Phase == | ||
Amorphous phases were a phenomenon of particular interest for the study of thin-film growth.<ref>{{cite journal | | Amorphous phases were a phenomenon of particular interest for the study of thin-film growth.<ref>{{cite journal |last1=Magnuson |first1=Martin |last2=Andersson |first2=Matilda |last3=Lu |first3=Jun |last4=Hultman |first4=Lars |last5=Jansson |first5=Ulf |title=Electronic structure and chemical bonding of amorphous chromium carbide thin films |journal=Journal of Physics: Condensed Matter |date=2012 |volume=24 |issue=22 |doi=10.1088/0953-8984/24/22/225004 |pmid=22553115 |arxiv=1205.0678 |bibcode=2012JPCM...24v5004M }}</ref> The growth of polycrystalline films is often used and preceded by an initial amorphous layer, the thickness of which may amount to only a few nm. The most investigated example is represented by the unoriented molecules of thin polycrystalline silicon films.{{efn|An initial amorphous layer was observed in many studies of thin polycrystalline silicon films.}}<ref name=Birk2001>{{cite journal |last1=Birkholz |first1=M. |last2=Selle |first2=B. |last3=Fuhs |first3=W. |last4=Christiansen |first4=S. |last5=Strunk |first5=H. P. |last6=Reich |first6=R. |title=Amorphous-crystalline phase transition during the growth of thin films: The case of microcrystalline silicon |journal=Physical Review B |date=2001 |volume=64 |issue=8 |article-number=085402 |doi=10.1103/PhysRevB.64.085402 |bibcode=2001PhRvB..64h5402B }}</ref> Wedge-shaped polycrystals were identified by [[transmission electron microscopy]] to grow out of the amorphous phase only after the latter has exceeded a certain thickness, the precise value of which depends on deposition temperature, background pressure, and various other process parameters. The phenomenon has been interpreted in the framework of [[Ostwald's rule]] of stages<ref name=Ostw1897>{{cite journal |last1=Ostwald |first1=W. |title=Studien über die Bildung und Umwandlung fester Körper |journal=Zeitschrift für Physikalische Chemie |date=1897 |volume=22U |pages=289–330 |doi=10.1515/zpch-1897-2233 }}</ref> that predicts the formation of phases to proceed with increasing condensation time towards increasing stability.<ref name="Buck1961"/><ref name="Birk2001"/>{{efn|Experimental studies of the phenomenon require a clearly defined state of the substrate surface—and its contaminant density, etc.—upon which the thin film is deposited.}} | ||
== Notes == | == Notes == | ||