title: [Effect of zirconia content on flexural strength and fracture toughness of dental zirconia toughened composite alumina ceramic].
abstract: OBJECTIVE
  To evaluate mechanical properties of zirconia toughened composite alumina (ZTCA) ceramic used for dental application, characterize the effect of different zirconia contents on mechanical properties of ZTCA.
  
  
  METHODS
  Dental alumina ceramic powder was prepared by sol-gel method, and four groups of ZTCA powders with different zirconia contents were prepared via surface-induced precipitation method. All five groups of powders were dry-pressed and then sintered to make standard specimens for mechanical tests. The flexural strength and fracture toughness of these specimens were evaluated, and the fractography was characterized by scanning electronic microscope (SEM). Phases of ZTCA were also determined using X-ray diffraction (XRD).
  
  
  RESULTS
  It was found that the flexural strength of ZTCA ceramics increases with ZrO2 content up to 30%, and decreases thereafter. ZTCA specimens containing 30% ZrO2 show the highest flexural strength, and the corresponding fracture toughness was 1.85 MPa x m(1/2). The XRD results of ZTCA ceramics showed the phase constituents of alpha-Al2O3, t-ZrO2 and a small amount of m-ZrO2.
  
  
  CONCLUSIONS
  The strengthening and toughening mechanisms of ZTCA depend on ZrO2 content. In the range of 15%-30% ZrO2, the stress-induced phase transformation toughening mechanism is dominant, while microcrack and deflection exist as the additional toughening mechanism when ZrO2 addition amount is above 30%.
authors.affiliation: Dept. of Prosthodontics, Guanghua School of Stomatology, Sun Yat-Sen University, Guangzhou 510055, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhao
authors.forename: Xin-Ping
authors.initials: XP
authors.lastname: Zhang
authors.forename: Xiang-Xia
authors.initials: XX
authors.lastname: Li
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Zhu
mesh_terms: D000537:Aluminum Oxide; D002516:Ceramics; D003776:Dental Porcelain; D008422:Materials Testing; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide