Electron irradiation induced vitrification at dislocations in quartz
Recent observations using the ‘weak beam’ electron microscopy technique of split images of dislocations in quartz have been interpreted as arising either from dissociation of the dislocations into partials1, or from a glassy (metamict) phase at the core2, resulting from irradiation damage. In this letter we describe observations of lattice images of near end-on dislocations in quartz, which enable us to distinguish between these two models.
Transmission Electron Microscope Study of the Dislocations in Plastically Deformed Synthetic Quartz
Transmission electron microscopy has been used to study the dislocations associated with the plastic deformation and recovery of single crystals of synthetic quartz. The crystals were deformed in compression at a constant strain rate under confining pressure over the temperature range 300 to 900°C. At 300°C rapid work-hardening occurs due to the development of a high uniform density of tangled dislocations. The dislocation substructures which are produced during deformation at higher temperatures correspond closely to the substructures which develop on annealing a work-hardened crystal. There is evidence that the rate of this recovery is strongly dependent upon the concentration of hydrogen present due to the influence of this impurity on dislocation climb. It is suggested, therefore, that the well-established hydrolytic weakening of quartz occurs when the rate of recovery exceeds the rate of work-hardening. This hypothesis predicts the observed variation of the hydrolytic weakening temperature with hydrogen concentration, strain rate, and crystal orientation. 
 
 
 
In Einkristallen von synthetischem Quarz wurden die Versetzungen, die mit der plastischen Deformation und Erholung verknupft sind, mittels Durchstrahlungselektronenmikroskopie untersucht. Die Kristalle wurden in Kompression bei einer konstanten Verformungsgeschwindigkeit unter beschranktem Druck im Temperaturbereich von 300 bis 900°C deformiert. Bei 300°C tritt eine schnelle Verfestigung auf, die durch die Entwicklung einer auserst gleichmasigen Dichte verwirrter Versetzungen hervorgerufen wird. Die Substrukturen der Versetzungen, die wahrend der Deformation bei hoheren Temperaturen erzeugt werden, stimmen weitgehend mit den Substrukturen uberein, die bei der Temperung eines verfestigten Kristalls entwickelt werden. Es gibt Hinweise dafur, das die Geschwindigkeit dieser Erholung stark von der Konzentration des anwesenden Wasserstoffs abhangt, was durch den Einflus dieser Verunreinigungen auf das Klettern der Versetzungen hervorgerufen wird. Es wird deshalb vorgeschlagen, das die gut bekannte hydrolytische Entfestigung von Quarz dann auftritt, wenn die Erholungsrate die Verfestigungsrate ubersteigt. Diese Hypothese sagt die beobachtete Anderung der hydrolytischen Entfestigungstemperatur mit der Wasserstoffkonzentration, Verformungsgeschwindigkeit und Kristallorientierung voraus.
Physical Processes in Inorganic Scintillators
BASIC PRINCIPLES AND PROCESSES Physical Mechanism of Scintillation Creation of Electron Hole Pairs Excitation and Emission of Luminescence Centers Scintillation Materials Halides Oxides and Oxide Systems Chalcogenides Glasses Interaction of Ionizing Radiation with Scintillators High Energy Photons Charged Particles Neutral Particles General Characteristics of Inorganic Scintillators Light Yield Duration of Scintillation Pulse Afterglow Temperature Response Optical Properties Radiation Hardness Density Emission Spectra Mechanical and Chemical Properties Physical Parameters Cost Consideration Scintillator Requirements in Various Applications High Energy Physics Intermediate Energy Physics Positron Emission Tomography Gamma Spectroscopy Energy Resolution Intrinsic Scintillator Resolution Nonproportional Response Time Resolution Low Energy Quanta and Electrons CONVERSION OF ELECTRONIC EXCITATIONS IN SOLIDS Charge Carrier Behaviors Delta Rays Secondaries Excitation of Luminescence Centers Effect of Ionization Density Energy Losses Simple Phenomenological Model Plasmon Model Polaron Model Scintillation Yield Spectra Vacuum Ultraviolet Region Ultrasoft X-Rays X-Rays Gamma Rays Heavy Ionizing Particles INTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Excitonic Luminescence Alkali Halide Crystals Alkaline-Earth Fluorides Ternary Halide Compounds Excitonic-Like Luminescence Cesium Iodide Tungstate and Molybdate Phosphors Core-to-Valence Transitions First Evidence for Radiative Core-to-Valence Transitions Excitation Spectra Emission Spectra Experiment Theory Luminescence Kinetics Experimental Theoretical Investigations Temperature Dependence of Luminescence Parameters Conditions of Detection Prospects for Research EXTRINSIC LUMINESCENCE OF INORGANIC SCINTILLATORS Thallium-Activated Halide Scintillators Crystals with NaCl-Type Structure Crystals with CsCl-Type Structure Other Thallium-Based and Thallium-Doped Crystals Crystals Containing Other ns2 Ions Bismuth Germanate (BGO) Sodium-Activated Cesium Iodide Rare-Earth-Activated Crystals General Considerations Europium-Activated Crystals Cerium-Activated Compounds Preliminary Comments LaF3-CeF3 Systems Cerium Chloride Barium Fluoride Gadolinium-Containing Crystals Lu- and Y-Containing Crystals Nd- and Pr-Activated Crystals DEFECT FORMATION BY IONIZING RADIATION Effect on Scintillator Characteristics Mechanisms of Defect Formation Efficiency of Defect Production Geometrical Factor Separation between F and H Centers Temperature Dependence of Production Efficiency Role of Halogen Ion Impurities Effect of Cation Impurities Formation Time of F-H Pairs Closing Comments References Index