HANDBOOK ON THE PHYSICS AND CHEMISTRY OF RARE EARTHS Advisory Editorial Board GIN-YA ADACHI Kobe, Japan WILLIAM J. EVANS Irvine, USA YURI GRIN Dresden, Germany SUZAN M. KAUZLARICH Davis, USA MICHAEL F. REID Canterbury, New Zealand CHUNHUA YAN Beijing, P.R. China Editors Emeritus KARL A. GSCHNEIDNER, JR† Ames, USA LEROY EYRINGw Tempe, USA † Deceased (2016) w Deceased (2005) North-HollandisanimprintofElsevier Radarweg29,POBox211,1000AEAmsterdam,TheNetherlands TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom Copyright©2016ElsevierB.V.Allrightsreserved Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans, electronicormechanical,includingphotocopying,recording,oranyinformationstorageand retrievalsystem,withoutpermissioninwritingfromthepublisher.Detailsonhowtoseek permission,furtherinformationaboutthePublisher’spermissionspoliciesandourarrangements withorganizationssuchastheCopyrightClearanceCenterandtheCopyrightLicensingAgency, canbefoundatourwebsite:www.elsevier.com/permissions. Thisbookandtheindividualcontributionscontainedinitareprotectedundercopyrightbythe Publisher(otherthanasmaybenotedherein). Notices Knowledgeandbestpracticeinthisfieldareconstantlychanging.Asnewresearchand experiencebroadenourunderstanding,changesinresearchmethods,professionalpractices,or medicaltreatmentmaybecomenecessary. Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledgein evaluatingandusinganyinformation,methods,compounds,orexperimentsdescribedherein.In usingsuchinformationormethodstheyshouldbemindfuloftheirownsafetyandthesafetyof others,includingpartiesforwhomtheyhaveaprofessionalresponsibility. Tothefullestextentofthelaw,neitherthePublishernortheauthors,contributors,oreditors, assumeanyliabilityforanyinjuryand/ordamagetopersonsorpropertyasamatterofproducts liability,negligenceorotherwise,orfromanyuseoroperationofanymethods,products, instructions,orideascontainedinthematerialherein. ISBN:978-0-444-63699-7 ISSN:0168-1273 ForinformationonallNorth-Hollandpublications visitourwebsiteathttps://www.elsevier.com/ Publisher:ZoeKruze AcquisitionEditor:PoppyGarraway EditorialProjectManager:ShellieBryant ProductionProjectManager:RadhakrishnanLakshmanan CoverDesigner:MarkRogers TypesetbySPiGlobal,India Contributors NumbersinParenthesesindicatethepagesonwhichtheauthor’scontributionsbegin. G. Adachi(1), FacultyofEngineering,Osaka University,Suita,Osaka,Japan C.D.S. Brites(339),CICECO—Aveiro InstituteofMaterials,UniversityofAveiro, Aveiro, Portugal L.D. Carlos(339),CICECO—Aveiro InstituteofMaterials,UniversityofAveiro, Aveiro, Portugal T. Hasegawa(1),Graduate SchoolofScienceandTechnology, NiigataUniversity, Niigata, Japan M.Hoshino(129),MineralResourceResearchGroup,NationalInstituteofAdvanced IndustrialScience andTechnology,Tsukuba,Japan S.W.Kim(1),Graduate SchoolofScienceandTechnology, NiigataUniversity, Niigata, Japan A.Milla´n(339),ICMA—InstitutodeCienciadeMaterialesdeArago´n,Universityof Zaragoza,Zaragoza,Spain J.A.Mydosh(293),KamerlinghOnnesLaboratoryandInstitute-Lorentz,Leiden University, Leiden,TheNetherlands L.Rademaker(293),KavliInstituteforTheoreticalPhysics,UniversityofCalifornia SantaBarbara,CA,UnitedStates K. Sanematsu(129),Mineral ResourceResearch Group,NationalInstituteof Advanced IndustrialScienceandTechnology, Tsukuba,Japan M.Sato(1), FacultyofEngineering,NiigataUniversity, Niigata,Japan Y.Shimomura(1),MitsubishiChemical Corporation,Odawara, Kanagawa,Japan K.Toda(1),GraduateSchoolofScienceandTechnology,NiigataUniversity,Niigata, Japan Y.Watanabe(129),AkitaUniversity, MiningMuseumofAkitaUniversity, Akita, Japan vii Preface These elements perplex us in our reaches [sic], baffle us in our speculations, and haunt us in our very dreams. They stretch like an unknown sea before us—mocking,mystifying,andmurmuringstrangerevelationsandpossibilities. SirWilliamCrookes(February 16,1887) Volume 49 of the Handbook on the Physics and Chemistry of Rare Earths adds four chapters to the series, covering subjects as diverse as phosphors forwhitelight-emittingdiodes,rare-earthmineralogyandresources,quantum critical matter and phase transitions in rare earths and actinides, and lantha- nide luminescent thermometers. The first chapter (Chapter 278) is devoted to luminescent materials for white light-emitting diodes. The subject is of importance with respect to energy-saving devices. Indeed, despite a sharp increase in the number of lighting devices worldwide, the share of electricity devoted to it is rather decreasing (about 12% presently). This is because of the prominent role playedbyrareearthphosphorsinimprovingtheefficiencyoflightingdevices, first in compact fluorescent lamps and presently in light-emitting diodes (LEDs).Theelectricity-to-lightconversionefficiencyhasincreasedbyafactor of 8–9 with respect to the traditional incandescent devices. In this chapter, the authorsfocusonLEDsbasedonblueindiumgalliumnitridechipscoatedwith one or several lanthanide-containing phosphors. Both yellow-emitting trivalent ceriummaterialsandpolychromaticphosphorsarediscussedwithrespecttothe choice of the matrix, of the active components, and of the synthetic methods yielding highly effective and both thermally and photo-stable materials. Rare earth resources are the subject of Chapter 279. A growing number ofcriticaltechnologiesarevitallydependentonrareearthelements,making use of their unique chemical, magnetic, and spectroscopic properties. This has resulted in some of the rare earths, such as Nd, Eu, Tb, and Dy, deemed criticalandprompted extensive effortsto find substitutes, whichishardand may not always be possible. Although not that rare in the earth crust, these elements are difficult to produce in the needed quantities because they always occur as intricate mixtures and because the compositions of these mixtures do not match the specific need for given elements. Geopolitical interferencesaddtotheproblem.Thereviewprovidesinsightintorareearth ix x Preface resources according to their various sources and focuses particularly on the more critical heavy lanthanides (Gd–Lu). With Chapter 280, the reader is transported into the select world of the- oretical physics. While we are familiar with first-order phase transitions such as liquid to gas (e.g., water evaporation) or liquid to solid (e.g., water freezing) that are characterized by a discontinuous change in the material’s properties and by the release or absorption of heat, second-order transitions such as ferromagnetic transitions are subtler because they are continuous, but they still feature discontinuity in the second derivative of the free energy. These transitions can be rationalized within the frame of well- established theories. When a second-order transition is thought to occur at zero temperature under the effect of pressure, magnetic field, or particle density, many unconventional properties develop around what is called a quantum critical point. The corresponding theories are challenging, and the authors discuss in detail the concept of quantum criticality in f-electron-based materials as well as successes and failures of existing the- ories such as the Hertz–Millis theory. The final chapter (Chapter 281) deals with temperature measurements. Temperature is an important thermodynamic parameter which is central to many chemical and biochemical processes. In particular, the delicate equilibrium prevailing in living cell critically depends on temperature. Measuring temperature is also vital in totally different fields, such as microelectronics or materials testing, for instance. While macroscopic determination of this parameter seems to be rather simple, for instance with thermistors or thermocouples, movingto microscopic or nanoscopic scale is muchmoreintricate.Thesizeofthe corresponding sensorsmustbereduced to molecular dimensions, and remote detection can no more rely on wire connections. Luminescence intensity is very often temperature dependent so that it offers a welcome possibility of designing noninvasive temperature micro- and nanosensors. The review concentrates on lanthanide sensors and describes how to optimize the thermal response of lanthanide-based luminescent thermometers, in particular the ratiometric single- and dual- center devices. CHAPTER 278: RARE EARTH-DOPED PHOSPHORS FOR WHITE LIGHT-EMITTING DIODES M. Sato*, S.W. Kim†, Y. Shimomura{, T. Hasegawa†, K. Toda†, and § G. Adachi *Faculty of Engineering, Niigata University, Niigata, Japan. E-mail: [email protected] †Graduate School of Science and Technology, Niigata University, Niigata, Japan { Mitsubishi Chemical Corporation, Odawara, Kanagawa, Japan § Faculty of Engineering, Osaka University, Suita, Osaka, Japan Preface xi In 1996, a new lighting device was proposed by Nichia Chemical Co., based on a blue InGaN LED chip coated with a yellow-emitting phosphor, cerium-doped yttrium aluminum garnet (Y Ce Al O , YAG:Ce3+). The 2.9 0.1 5 12 lighting device proved to have numerous advantages over traditional incan- descent and fluorescent lamps, such as small size, long lifetime, robustness, fast switching, and high efficiency. Phosphor materials such YAG:Ce3+ play an unquestionable role for achieving high color-quality white emission in LED technology. However, conventional phosphors used in fluorescent lighting or displays are not good candidates for LED lighting because they are optimized for excitation at the wavelength of a mercury discharge tube at 254nm, while InGaN chips emit in the blue. The aim of this review is to provide clues for the design of efficient lanthanide-based LED phosphors. After a description oftheprinciples ofLED lighting and phosphorrequire- ments, the structures and luminescence properties of LED phosphors are pre- sented. The classification of phosphors is primarily based on the chemical composition such as oxide, nitride, and sulfide; on the emission color such as yellow, green, and red; and, finally, on the actual chemical formula. This is becauseitisconvenienttounderstandthephosphorcharacteristicsonthebasis ofthenatureofchemicalbonding,whichcontrolstheenergyofelectronictran- sitions,inthesolid state.Inpracticalapplicationsfor white lightLED devices, powdertechnologyisimportantsothatthechapterdescribessynthesismethods of phosphor particles including morphology control. Implementation of phos- phorsinLEDlightingdevicesisdealtwithinthelastsection,aswellasrecent progresses in remote phosphors and wafer-level packaging. CHAPTER 279: REE MINERALOGY AND RESOURCES M. Hoshino*, K. Sanematsu*, and Y. Watanabe† *MineralResourceResearchGroup,NationalInstituteofAdvancedIndustrial ScienceandTechnology,Tsukuba,Japan.E-mail:[email protected] †Akita University, Mining Museum of Akita University, Akita, Japan xii Preface Preface xiii Recent increase of the demand for rare earth elements (REEs), especially dysprosiumandterbiumusedinthepermanentmagnetindustry,ismodifying theindustrialapproachtoREEmineralogyandresources.Thisisamplifiedby the REE supply restrictions outside of China and by the fact that rare earths are never mined individually but always as mixtures with various composi- tions. These compositions however do not necessarily correspond to the demand for individual rare earths. Some elements are in surplus (La, Ce), while other ones are in tight supply (or more utilized) and are classified as “critical” (yttrium, neodymium,europium, terbium, dysprosium). Exploration has now been extended worldwide to secure the supply of REEs, especially the heavier ones (HREEs, Gd–Lu) that are globally three times less abundant than the lighter rare earths. In recent years, various attempts have been made to produce HREEs from unconventional sources, such as peralkaline igneous rocks, which have traditionally not been regarded as a REE source, or deep- sea muds (see Vol. 46, Chapter 268). ThechapterreviewsthepotentialsourcesofREEs,withafocusonHREEs, which areregardedasthemostcriticalgroupofelementsforthefuturegreen technologies. It starts with a description of the geochemistry and mineralogy of rare earth elements before focusing on rare earth deposits. In this section, theirclassificationintocarbonatite,peralkalinerocks,ironoxideapatite,hydro- thermal vein, ion-adsorption clays, and placer deposits is presented. More detailedpropertiesofionadsorption andapatitedepositsaredepictedinview oftheimportanceofheavierrareearthelements.Theauthorsconcludethatin thefuturethemostpromisingsourceofrareearthswillbeapatiteores. CHAPTER 280: QUANTUM CRITICAL MATTER AND PHASE TRANSITIONS IN RARE EARTHS AND ACTINIDES L. Rademaker* and J.A. Mydosh† *Kavli Institute for Theoretical Physics, University of California Santa Barbara, CA, United States. E-mail: [email protected] †Kamerlingh Onnes Laboratory and Institute-Lorentz, Leiden University, Leiden, The Netherlands. E-mail: [email protected] → |g – g|uz c T Quantum critical Ordered phase Quantum disordered g c QCP g → xiv Preface Many intermetallic compounds based on rare earth and actinide ele- ments display unusual electronic and magnetic properties in that standard Fermi liquid theory is not applicable. However, theoretical developments have shown that these properties can be rationalized within the frame of the “quantum-phase transition” (QPT) concept. In this chapter the authors discuss quantum criticality, the notion that properties of a material are governed by the existence of a phase transition at zero temperature. The point where a second-order (continuous) phase transition takes place is known as a quantum critical point (QCP). Materials that exhibit quantum critical points can be tuned through their QPT by, for example, pressure, chemical doping or disorder, frustration, and magnetic field. The study of QPTs was initially theoretically driven, showing that high-temperature properties of a material with a QPT are directly influenced by the proper- ties of the QCP itself. The chapter starts by discussing the predictions of quantum critical and Hertz–Millis (H–M) theories. Experimentally, the authors mainly limit themselves to f-electron-based materials: the rare earths Li(Ho,Y)F , 4 Ce(Cu,Au) , and YbRh Si , the cerium series Ce(Co,Rh,Ir)In , and one 6 2 2 5 actinide-based material, URu Si . These heavy fermion 4f or 5f metals rep- 2 2 resent prototype materials of quantum critical matter, and their experimen- tal signatures are critically reviewed as well as their evolving theoretical descriptions. The authors then elaborate on the shortcomings of H–M the- ory and list attempts toward better theories. Difficulties arising in hidden QCPsevidencethechallengesandopportunitiesassociatedwiththeconcept of QPT. The review concludes with the description of other manifestations of QPTs beyond the rare earths and actinides. CHAPTER 281: LANTHANIDES IN LUMINESCENT THERMOMETRY C.D.S. Brites*, A. Milla´n†, and L.D. Carlos* *CICECO—Aveiro Institute of Materials, University of Aveiro, Aveiro, Portugal. E-mail: [email protected] †ICMA—Instituto de Ciencia de Materiales de Arago´n, University of Zaragoza, Zaragoza, Spain Preface xv Luminescent ratiometric thermometers combining high spatial and tem- poral resolution at the micro- and nanoscale, where the conventional meth- ods are ineffective, have emerged over the last decade as an effervescent field of research, essentially motivated by potential applications in nanotech- nology, photonics, and biosciences. Applications of nanothermometry are developing in microelectronics, microoptics, photonics, micro- and nanoflui- dics, nanomedicine, and in many other conceivable fields, such as thermally induced drug release, phonon-, plasmonic-, magnetic-induced hyperthermia, and wherever exothermal chemical or enzymatic reactions occur at submi- cron scale. Among suitable luminescent thermal probes, trivalent lanthanide-based materials play a central role due to their unique thermo- metric response and intriguing emission features such as high quantum yield, narrow bandwidth, long-lived emission, large ligand-induced Stokes shifts, and ligand-dependent luminescence sensitization. The chapter offers a general overview of recent examples of single- and dual-center lanthanide-based thermometers, emphasizing those working at nanometric scale. Important focus is given to how to quantify their perfor- manceaccordingtotherelevantparameters:relative sensitivity,experimental uncertainty on temperature, spatial and temporal resolution, repeatability (or test–retest reliability), and reproducibility. The emission mechanisms supporting single- and dual-center emissions are reviewed, together with the advantages and limitations of each approach. Illustrative examples of the rich variety of systems designed and developed to sense temperature are provided and explored: crystals of ionic complexes, molecular thermometers,