Anthony Diaz, Ph.D. 

Assistant Professor Inorganic Chemistry

Phone: (509) 963-2818
Fax: (509) 963-1050
Email: diaza@cwu.edu
Office: Science Building 302C

Education

• 1996 - PhD, Oregon State University
• 1993 - MS, Western Washington University
• 1991 - BS, University of Washington

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Research Interests

My research group focuses on developing a fundamental understanding of energy absorption and transfer processes in solid state luminescent materials. We are also interested in what happens structurally and electronically to these materials when they are damaged by high-energy radiation. This kind of work is critical to the development of mercury-free lighting systems, and is also of considerable interest to the plasma display panel industry.

In general a luminescent material (a phosphor) consists of a crystalline host into which a few mole percent of a luminescent atom (the activator) is doped. Zn₂SiO₄:Mn²⁺, for example, is the green phosphor in plasma display panels. This material is just the common mineral Willemite with about 10% of the Zn atoms replaced by Mn. In standard lighting applications like a Hg-based fluorescent lamp, the ultraviolet (UV) photons from the Hg discharge are absorbed directly by the activator atom (the host is transparent to these wavelengths), and the excited activator emits a photon. For technologies based on a Xe discharge, like plasma display and Hg-free lamps, the excitation energy is high enough (vacuum ultraviolet) that it is actually absorbed first by the host lattice. The energy must then be transferred to the activator before emission of a photon can occur. These processes are contrasted here for a hypothetical system in which the activator emits a green photon:

We are particularly interested in the piece labeled Transfer. There are several mechanisms for the transfer of that energy, but little is know about what host conditions are ideal for good transfer. In addition, exposure to vacuum ultraviolet photons tends to damage these phosphors - decreasing the brightness or changing the color - but the details of the damage mechanisms are not well understood. Thus, degredation studies are also of interest. This work is a lot of fun because it brings in knowledge and resources from a variety of fields in chemistry and physics, including crystallography, phase equilibria, solid state synthesis, luminescence, spectroscopy, and band theory. My research group is studying these phenomena using UV and VUV spectroscopy, as well as X-ray diffraction.

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Background

• Principal Engineer, OSRAM SYLVANIA (1996 - 2000) I came to CWU from the phosphor R and D group at OSRAM SYLVANIA, where I did a lot of work on the development of phosphors for plasma display panels. As part of that work we solved an interesting puzzle about the blue phosphor, BaMgAl₁₀O₁₇:Eu²⁺. We used X-ray diffraction and luminescence spectroscopy to show that the phase diagram for the BaO - MgO - Al₂O₃ system needed to be modified.
• Ph.D., Oregon State University (1993 - 1996) I did my PhD work with Professor Douglas Keszler, who's research group is part of the Center for Advanced Materials Research at OSU. We developed a new model to explain the large differences in the optical properties of Eu²⁺ in various borate hosts. The model is unique in that it focuses on the environments of the O atoms in these materials, rather than on the cation coordination environments.
• M.S., Western Washington University (1991 - 1993) I did my MS work with Professor Mark Bussell. We looked at the surface chemistry of alumina-supported catalysts that are used in petroleum reforming: The details of this kind of science are pretty interesting, and you can learn all about it at Dr. Bussell's web site.
• B.S., University of Washington (1990 - 1991) At UW I did undergraduate research with Professor Charles Campbell. This was more surface chemistry stuff, this time looking at the decomposition of cyclic hydrocarbons on a single crystal Pt surface. Dr. Campbell had developed a clever method for using surface Bi to trap reaction intermediates.

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Publications

• B. Dawson and A. L. Diaz, "Crystal Chemistry, Defect Chemistry, and Degradation Processes in BaMgAl₁₀O₁₇:Eu²⁺," Proceedings of the 12th International Display Workshops, 1, 509 - 512 (2005).
• B. Dawson, M. Ferguson and A. L. Diaz, "Mechanisms of VUV Damage in BaMgAl₁₀O₁₇:Eu²⁺," Chemistry of Materials, 16, 5311 - 5317 (2004).
• A. L. Diaz, "Semiconductors," Chemistry: Foundations and Applications J. J. Lagowski, ed. Macmillan Reference USA (2004) pp. 117 - 123.
• B. Howe and A. L. Diaz, "Characterization of Host Lattice Emission and Energy Transfer in BaMgAl₁₀O ₁₇:Eu²⁺," Journal of Luminescence, 109, 51 - 59 (2004).
• V. Pike, S. Patraw, A. L. Diaz and B. G. DeBoer, "Defect Chemistry and VUV Optical Properties of the BaMgAl₁₀O ₁₇:Eu²⁺- Ba_0.75Al ₁₁O_17.25:Eu²⁺ Solid Solution," Journal of Solid State Chemistry, 173, 359- 366 (2003).
• D. B. Bolstad and A. L. Diaz, "Synthesis and Characterization of Nanocrystalline Y₂O₃:Eu³⁺ Phosphor:An Upper-Division Inorganic Chemistry Laboratory," Journal of Chemical Education, 79, 1101 - 1104 (2002).
• A. L. Diaz, B. G. DeBoer and C. F. Chenot, "Effects of Stoichiometry on the Luminescence and Thermal Stability of BaMgAl₁₀O₁₇:Eu²⁺, " 19th International Display Research Conference Proceedings, 65 - 68 (1999). 
• D. A. Keszler and A. L. Diaz, "Eu²⁺ Luminescence Color: A Structure - Property Relationship, "Materials Research Society Symposium Proceedings, 453, 247 - 252 (1997).
• A. L. Diaz and D. A. Keszler, "Eu²⁺Luminescence in the Borates X₂Z(BO₃)₂ (X = Ba, Sr; Z = Mg, Ca)," Chemistry of Materials, 9, 2071 - 2077 (1997).
• A. L. Diaz and D. A. Keszler, "Red, Green and Blue Eu²⁺Luminescence in Solid State Borates: A Structure - Property Relationship," Materials Research Bulletin, 31, 147 - 151 (1996).
• A. L. Diaz, C. Radzewich and M. Wicholas, "Synthesis and ¹H VT-NMR Conformational Analysis of Bis (π cyclopentadienyl) Titanium Pentasulfide: An Experiment for an Integrated, Advanced Laboratory Course," Journal of Chemical Education,72, 937 - 938 (1995).
• A. L. Diaz, W. W. C. Quigley, H. D. Yamamoto and M. E. Bussell, "Infrared Spectroscopy and Temperature Programmed Desorption Study of CO on Rh/Al₂O₃Catalysts: Probing Overlayer and Support Sites," Langmuir, 10, 1461 - 1471 (1994).
• A. L. Diaz and M. E. Bussell, "An Infrared Spectroscopy and Temperature Programmed Desorption Study of CO on MoO₃/Al₂O₃ Catalysts: Quantitation of the Molybdena Overlayer," Journal of Physical Chemistry, 97, 470 - 477 (1993).
• M. B. Hugenschmidt, A. L. Diaz and C. T. Campbell, "Interaction of Cyclohexadiene with Pt(111) Studied by BPTDS and HREELS," Journal of Physical Chemistry, 96, 5974 - 5978 (1992).
• F. C. Henn, A. L. Diaz, M. E. Bussell, M. E. Domagala, M. B. Hugenschmidt and C. T. Campbell, "The Decomposition of Cyclohexene on Pt(111): A BPTDS, HREELS Study," Journal of Physical Chemistry, 96, 5965 - 5974 (1992).

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U.S. Patents 

• #6,303,051 A. L. Diaz and C. F. Chenot, "Phosphate Treated Silicate Phosphor", Oct. 16, 2001. 
• #6,149,839 A. L. Diaz and J. A. Yurchisin, "Cation-treated Silicate Phosphor", Nov. 21 2000. 
• #5,976,413 A. L. Diaz, C. F. Chenot and S. A. Sonner, "Method of Preparing a Lead and Manganese Co-activated Calcium Metasilicate Phosphor", Nov. 2 1999.

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