title: [Effect of three kinds of rare earth oxides on chromaticity and mechanical properties of zirconia ceramic].
abstract: OBJECTIVE
  To evaluate the colouration of zirconia ceramic by adding three kinds of rare earth oxides. The influence of the pigments concentration on the mechanical properties and the microstructure was also analyzed.
  
  
  METHODS
  Added different concentrations of CeO(2), Er(2)O(3) and Pr(6)O(11) in tetragonal zirconia poly crystals stabilized with 3 mol% yttria (3Y-T2P) powder, compacted at 200 MPa using cold isostatic pressure, and sintered to 1 400 degrees C. The heating rate was 150 degrees C/h and the dwelling time was 2 hours. The chromaticity of sintered bodies was measured with chroma meter. The relative density, hardness, flexure strength and fracture toughness were investigated as well. The phase stability of the colorized and pure zirconia was evaluated by X-ray diffraction (XRD) using an automated diffractometer. The microstructures of the specimens were evaluated by scanning electron microscope (SEM).
  
  
  RESULTS
  Several kinds of color achieved by the different pigments praseodym oxide, cerium oxide and erbium oxide were presented in the CIELab system. The a* value increased with the added amount of Er(2)O(3), while b* value rose with the increasing amount of CeO(2) and Pr(6)O(11). However, three pigments failed to decrease L* value and the sintered body appeared too bright. Adding three pigments influenced flexure strength of zirconia ceramic significantly, but had little influence on the hardness and fracture toughness. Microscopy revealed the relationship between the porosity and shapes of grains was correlated to strength of the diphase ceramics. No additional phase could be detected by XRD, except t-ZrO(2) in all colorized samples after sintering at 1 400 degrees C for 120 min.
  
  
  CONCLUSIONS
  Zirconia ceramic can be colorized by CeO(2), Er(2)O(3), and Pr(6)O(11). Pigments even in a small amount influence the mechanical properties of the colorized zirconia material, which necessitates further investigation.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200011, China. fredzc@online.sh.cn
authors.forename: Hui
authors.initials: H
authors.lastname: Huang
authors.forename: Fu-qiang
authors.initials: FQ
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Lian
authors.initials: L
authors.lastname: Gao
mesh_terms: D004396:Coloring Agents / Q000494:pharmacology*; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis; D008674:Metals, Rare Earth / Q000494:pharmacology; D010087:Oxides / Q000494:pharmacology; D017797:Prosthesis Coloring; D015040:Zirconium / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D008674:Metals, Rare Earth; D010087:Oxides; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide