Skip to main content
Article thumbnail
Location of Repository

Microstructure and properties of (rare earth) doped oxide ceramics

By James M. Perkins


A study of alumina (AI203 ) and magnesium aluminate spinel (MgAb04) was undertaken\ud with the aim of investigating the changes in properties and microstructural characteristics\ud upon doping with specific rare earth elements.\ud Microscopic imaging and analysis of RE doped polycrystalline oxide ceramics has shown\ud convincing evidence for monolayer segregation of RE cations to grain boundaries. State\ud of the art aberration corrected scanning transmission electron microscopy (SuperSTEM I\ud Daresbury Laboratories) has shown monolayer segregation to grain boundaries, and\ud atomic resolution parallel electron energy loss spectroscopy has confirmed the presence\ud of the RE cation at the grain boundary position. The region affected by segregation\ud has been shown to extend no further than one monolayer from the centre of the grain\ud boundary with RE cations occupying matrix cation boundary sites.\ud The effect of RE dopants on the powder processing and sintering of high purity commercial\ud grade precursor powders was investigated. Differences were found between doped\ud alumina and spinel in the sintering whereby the alumina grain growth was restricted\ud by grain boundary mobility such that the grain size was reduced for a given sintering\ud temperature. The grain size of spinel was unaffected by sintering temperature.\ud Differences in the fracture behaviour between doped alumina and spinel was found.\ud The alumina samples manifested a change from trans-granular fracture to inter-granular\ud fracture due to the addition of RE dopants. Spinel did not show such an effect. Alumina\ud was shown to posess an approximate Hall-Petch relationship between hardness and\ud grain size for both doped and undoped samples, such that sub-micron grain size samples\ud posessed high hardness.\ud Optical characterisation has shown the potential for the use of fine grained RE doped\ud alumina and spinel samples for hard window applications. A reduction in the grain size\ud of alumina to below 1 μm leads to a change in the scattering mechanism, thus reducing\ud low angle scatter and birefringence due to the refractive index mismatch. The benefits\ud to optical properties are in addition to the benefits in mechanical properties of a submicron\ud grain structure

Topics: QD
OAI identifier:

Suggested articles


  1. (2005). [13] Ceramic industry magazie, online content. industry news,
  2. (2005). [138] Transparent polycrystalline sintered ceramic of cubic crystal structure,
  3. (1962). [2] Transparent alumina and method of preparation,
  4. (1968). [43] Alumina ceramic,
  5. (1973). [57] Transparent articles of aluminium oxide and methods of manufacturing said articles,
  6. (2002). [7] Engineering our future through ceramics, Report of the Advanced Ceramics Task Force,
  7. (1997). [90] [91] Image j, Java image processing software.
  8. 8.14: ' "i'ible light scatter images captured on a CCD of various grain size Ttti doped alumina ample : (a) Unobstructed beam) (b) 0.74 J-Lm) (c) 1.12 J-L) (d) 2.08 J1 and (e) 4·61 urn. 250 - - Unobstructed beam
  9. (1981). A critical evaluation of indentation techniques for measuring fracture toughness: I, Direct crack measurements. doi
  10. (2002). A study of grain-boundary structure in rare-earth doped aluminas using an EBSD technique.
  11. (2000). Advanced ceramics: At the cutting edge, ceramics in the cutting tool market,
  12. (1991). An introduction to grain boundary fracture in metals. The institute of metals, doi
  13. (2005). Analysis and spectroscopy of rare earth doped magnesuim aluminate spinel" doi
  14. (2004). Atomic structure of a (2 x 1) Reconstructed NiSi2jSi (001) Interface. Physical Review Letters, doi
  15. (2001). Benefits of microscopy with super resolution.
  16. (2002). Cation segregation in Nb16WlS094 using high angle annular dark field scanning transmission electron microscopy and image processing. doi
  17. (2001). Ceramic Cutting Tools. Industrial ceramics, doi
  18. (2004). Characterisation of fine-grained oxide ceramics." doi
  19. (2001). Characterization of structural alumina ceramics used in ballistic amour and wear applications.
  20. (2005). Codoping and Grain-Boundary Cosegregation of Substitutional Cations in alpha-alumina: A Density-Functional-Theory Study. doi
  21. (2000). Colloidal Processing of Ceramics. doi
  22. (2000). Colour and the optical properties ofmaterials.
  23. Compaction and Sintering Behaviour of Bimodal Alumina Powder Suspensions by Pressure Filtration. doi
  24. (2002). Comparison between SEM and TEM Imaging Techniques to Determine Grain-Boundary Wetting in Ceramic Polycrystals. doi
  25. (1994). Creep of Duplex Microstructures. doi
  26. (2005). Degradation of magnesium aluminum spinel by lithium fluoride sintering aid. doi
  27. (1997). Dopant Distributions in Rare-Earth-Doped Alumina. doi
  28. EDS spectra from (a) grain centre and (b) grain boundary of Yb doped
  29. (1995). Effect of grain boundary dopants and mean grain size on tribochemical behaviour og highly purified alpha-alumina in the mild wear regime. doi
  30. (2003). Effect of Grain Boundary Microcracking on the light transmittance of sintered transparent mga1204. doi
  31. (2004). Effect of nd203 Doping on the Densification and Abnormal Grain Growth behaviour of High-Purity Alumina. doi
  32. (1998). Effectiveness of hip prostheses in primary total hip replacement: A critical review of evidence and an economical model. Health technology assessment,
  33. (1999). Effects of Yttrium Doping alpha-Alumina: I, Microstructure and Microchemistry. doi
  34. (1986). Electron Energy Loss Spectroscopy in the Electron Microscope. doi
  35. (1991). Electron radiation damage of alpha-alumina[2].
  36. (1991). Engineered Materials Handbook volume 4 -Ceramics and Glasses: Engineering properties ofsingle oxides,
  37. (2005). Evaluation of Hot Isostatic Pressing Parameters on the optical properties of spinel. doi
  38. (2000). Fabrication of Translucent Magnesium Aluminate Spinel Ceramics. doi
  39. (2004). Finnis. Bismuth embrittblement of copper is an atomic size effect. nature, doi
  40. (2003). First-principles analysis of cation segregation at grain boundaries in alpha-alumina. doi
  41. (1984). Fracture of tranlucent alumina - Temperature dependance and influence of CaO dope.
  42. (1984). Fracture of translucent alumina: temperature dependance and influence of CaO dope. doi
  43. (1957). Grain Boundaries in Metals. doi
  44. (1999). Grain boundary bonding state and 206fracture energy in small amount of oxide-doped fine-grained A1203.
  45. (2006). Grain Boundary Strengthening in Alumina by Rare Earth Impurities. doi
  46. (1972). Grain-Boundary Segregation in A1203.
  47. (1978). Grain-Boundary Segregation in MgO-Doped A1203.
  48. (1985). Grain-growth kinetics for alumina in the absence of a liquid phase. doi
  49. (1998). High-temperature creep resistance in rare-earth-doped fine-grained alumina. doi
  50. (2004). Imaging at the picoscale. doi
  51. (2001). Impurity effects on grain boundary strength in structural ceramics. doi
  52. (1998). Indentation fracture toughness of high purity submicron alumina. doi
  53. (1973). Influence of Additives on the Microstructure of Sintered A1203. doi
  54. (2000). Influence of grain size on the indentation-fatigue behavior of alumina. doi
  55. (1997). Influence of stoichiometry on fracture behaviour of magnesium aluminate spinels at 1200C. doi
  56. (1998). Influence of Yttrium Doping on Grain Misorientation in Aluminium Oxide. doi
  57. (1975). Interface adsorption, embrittlement and fracture in metallurgy, volume 53. Surface Science, doi
  58. (1975). Interface adsorption, embrittlement and fracture in metallurgy. doi
  59. (1977). Interfacial Segregation.
  60. IR transmission spectra are plotted in figure 8.9. There are no obvious absorption peaks and all samples showed good IR transparency with the cutoff at '"'-'1500 -
  61. (1974). Light scattering by pores in polycrystalline materials: Transmission properties of alumina. doi
  62. (1982). Light scattering by small particles. doi
  63. (1973). Microstructural changes during heat treatment of sintered alumina. doi
  64. (2004). Microstructure-property relations in fine-grained oxide ceramics. doi
  65. (1992). Modern Ceramic Engineering. Marcel Dekkar inc.,
  66. (2002). Multiscale aspects of the influence of Yttrium on microstructure, sintering and creep of alumina. doi
  67. (2002). New Processing Techniques for Advanced Ceramics.
  68. (2000). Novel Powder Processing Methods for Advanced Ceramics. doi
  69. o 200 400 600 800 Wavelength / nm 1000 1200 Figure 8.17: Plot of wavelength against RIT for a set of Tm doped alumiruis, with model data shown as a solid line and experimental results shown as individual points.
  70. (2004). Observation of rare-earth segregation in silicon nitride ceramics at subnanometre dimensions. doi
  71. (2003). of ECerS.,
  72. (2002). of the West Indies, Chemistry homepage.,
  73. (2000). Optical Materials. Academic press, doi
  74. (1998). Optical properties of ALON (aluminium oxynitride). Infra-red Phys. and Tech., doi
  75. (1994). Principles ofelectron microscopy.
  76. (1963). Reactions between refractory oxides and graphite. doi
  77. (1976). Revised Effective Ionic Radii and doi
  78. (2002). Role of segregating dopants on the improved creep resistance of aluminium oxide.
  79. (1964). Role of Solute Segregation at Grain Boundaries During Final-Stage Sintering of Alumina. doi
  80. (1999). Scanning Transmission Electron Microscopy Analysis of Grain Boundaries in Creep-Resistant Yttrium and Lanthanum-Doped Alumina Microstructures. doi
  81. (2003). Setti. Role of magnesia and silica in alumina microstructure evolution. doi
  82. Silica and Magnesia Dopant Distribution in Alumina by High-Resolution Scanning Secondary Ion Mass Spectrometry. doi
  83. (1961). Sintering Crystalline Solids. I. Intermediate and Final State Diffusion Models. doi
  84. (1961). Sintering Crystalline Solids. II. Experimental Test of Diffusion Models in Powder Compacts. doi
  85. (1968). Solubilities of Magnesia, Titania and Magnesium Titanate in Aluminium Oxide. doi
  86. (2000). Structural Features of Y-Saturated and Supersaturated Grain Boundaries in Alumina. doi
  87. (2004). Sub-Angstrom Resolution with Aberration-Corrected TEM: 211Present and Future. doi
  88. (1972). Subsolidus phase equilibriums in aluminium oxidechromium (III) oxide. nature,
  89. (1999). Superfast densification of oxide/oxide ceramic composites. doi
  90. (2000). The amptiac newsletter. doi
  91. (1906). The Collected works, vol 1. Longmans,
  92. (2005). The effect of rare earth dopants on grain boundary cohesion in alumina. in press, doi
  93. The fracture behaviour of the two oxides has been studied using two methods. Firstly 15918.5 18.0 • undoped spinel 17.5 • Tm doped spinel • 17.0 ro 16.5
  94. (1961). The nature of the chemical bond. doi
  95. (1975). The quantitative analysis of thin specimens. doi
  96. (1949). The theoretical resolution limit of the electron microscope. doi
  97. (1999). Towards sub-angstrom electron beams. doi
  98. (2004). Translucent (alpha)-sialon ceramics by hot pressing. doi
  99. (1996). Transmission Electron Microscopy, A Textbook for Materials Science. doi
  100. (1991). Transmission optical properties of polycrystalline alumina with submicron grains. doi
  101. (2002). Transparent Alumina with Submicrometer Grains by Float Packing and Sintering. doi
  102. (2003). Transparent Alumina: A LightScattering Model. doi
  103. (2005). Transparent ceramic lamp envelope materials. doi
  104. (2004). Transparent Fine-Grained Oxide Ceramics. doi
  105. (2004). Transparent fine-grained oxide ceramics." ,Key Engineering Materials., doi
  106. (1979). Transparent hot-pressed alumina, II: Transparent versus Translucent alumina. doi
  107. (2000). Transparent Spinel Development. doi
  108. (2001). Transparent YAG from powder prepared by homogeneous precipitation reaction -
  109. (1996). Transport properties of titanium-doped alpha-alumina: experimental results. doi
  110. (2002). Wear performance of fine grained alumina produced during the sparkciba project. unpublished,
  111. (2002). X-Ray Absorption Near-Edge Structure of Grain-Boundary-Segregated Y and Zr in Creep-Resistant Alumina. doi
  112. (1986). Yttrium Segregation and YAG Precipitation at doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.