CAPAD processing of Rare Earth Doped Zirconia for High Temperature Light Emission Applications

Doctor of Philosophy, Graduate Program in Mechanical Engineering
University of California, Riverside, December 2014
Dr. Javier Garay, Chairperson

The high fracture toughness of stabilized zirconia makes it one of the most widely applicable high  temperature  structural  materials.  However,  it  is  not  typicality  considered  for  optical applications  since  the  microstructure  achieved  by  traditional  processing  makes  it  opaque. The aim of this dissertation is to develop processing methods for the introducing new functionalities  of  light  transparency  and  light  emission  (photoluminescence)  and  to  understand the  nanostructure-property  relationships  that  make  these  functionalities  possible. A processing  study  of  rare-earth  (RE)  doped  Zirconium  Oxide  (ZrO2,  zirconia)  via  Current Activated  Pressure  Assisted  Densification  (CAPAD)  is  presented.  The  role  of  processing temperature and dopant concentration on the crystal structure, microstructure and properties of the RE: ZrO2 is studied. Microstructural shows sub-100 nm grain size and homogeneous dopant  distribution. X-ray  diffraction and Raman analysis show that with  increased dopant concentration the material changes from monoclinic to tetragonal. Structural analysis shows the material shows high hardness and toughness values 30% greater than similarly processed
yttria-stabilized   zirconia.   Despite   birefringence   in   the   tetragonal   phase,   optical characterization  is  presented  showing  the  samples  are  both  highly  transparent  and photo-luminescent.  Special  attention  is  paid  to  analyzing  structural  and  photoluminescence development  during  densification,  as  well  as  the  role  of  oxygen  vacancies  on  the  optical properties of the densified material. This material is shown to be a promising candidate for a number  of  applications  including  luminescence  thermometry  and  high  temperature  light emission.