In-situ High Temperature Ferroelastic Phase Transformations in Oxide Ceramics

Waltraud M. Kriven, University of Illinois at Urbana-Champaign, DMR 0211139

Accomplishments:•Significant instrumental improvements in conducting rapid high temperature XRD experiments:

•The CIP detector is a one-dimensional detector which

•simultaneously records XRD pattern for 2θ range of 0° to 38°

•has intrinsic resolution ~ 0.007º.

•can acquire entire XRD pattern in ≤ 30 seconds.

•In-situ high temperature phase transformation investigations on powder oxide ceramics including Ta2O5, HfO2 – x Ta2O5 (for x = 0 to 6 mol%) compounds, RNbO4 (where R = Y, Dy, or La), DyVO4, and CePO4 analysis is underway.

IntroductionHigh temperature phase transformations in oxide ceramics are being studied in-situ, in air, using a thermal-image quadrupole lamp furnace (QLF) in conjunction with synchrotron radiation. The emphasis is on oxide materials exhibiting polymorphic phase transformations of ferroelastic nature, at elevated temperatures (up to 2000ºC). Potential applications include tough ceramic composites, actuators and shape memory ceramics.

Figure 1. The curved image plate (CIP) detector system at the XOR/UNI 33-BM-C beam line at APS in ANL, IL, is used in conjunction with the quadrupole lamp furnace for rapid in situ high temperature XRD (HTXRD) measurements, up to 2000° C in air. This set up was used to study phase transformations in oxide ceramics including Ta2O5, RNbO4 (where R = Y, Dy, or La), etc. The CIP detector was designed and built under an AFOSR DURIP award number FA9550-04-1-0345.

Figure 2. Selected 2 ranges of diffraction data collected on cooling high temperature form of Ta2O5 indicated peak splitting. The temperature dependence of (0 1 7), (0 1 11) and (1 1 6) peaks is shown. Ta2O5 underwent abrupt and apparently displacive phase transformations at ~1273 and ~613 K during heating/cooling. This work was done in collaboration with Geoffrey Brennecka (Ph.D. May'06) an NSF Fellow working with Prof. David A. Payne at UIUC.

Education:Ms Bo Moon Yee, a graduate student, completed her MS in Materials Science and Engineering, and has started her work with a federal agency. Melissa Smith, an African-American undergraduate who has been an REU student for 4 years has graduated and is starting Ph.D. studies at MIT this Fall 2006. Mike Mulholland, an REU student for 2 years has started his graduate studies at Northwestern University in Fall 2005. Several students, both undergraduate and graduate, as well as postdoctoral research fellows had the opportunity to learn, develop and design instrumentation, as well as become trained in conducting in situ, high temperature XRD experiments at synchrotron facilities. Ryan Haggerty, a graduate student, was one of the 60 students across the country who were selected to attend the National School on Neutron and X-ray Scattering at Argonne National Laboratory, Argonne IL.

In-situ High Temperature Ferroelastic Phase Transformations in Oxide Ceramics

Waltraud M. Kriven, University of Illinois at Urbana-Champaign, DMR 0211139

Outreach:Students and PI together have presented their findings at more than 40 international conferences, as contributed talks, and invited and plenary lectures over the last two years. The CIP detector developed by the PI’s research group was featured as a Novel X-ray Technique and Instrumentation in the APS Annual Report, May 2005. Besides being an advisor and mentor to students, the PI has served as Chair of the Engineering Ceramics Division of the American Ceramic Society; was elected Academician in the World Academy of Ceramics; has co-edited 14 books; was an NSF panel reviewer; and served as a review instructor for the Illinois Society of Professional Engineers. The PI has also started a series of lectures on Special Topics in Science and Engineering at the local High School, to encourage high school students to learn more about materials science and engineering. The PI also serves on the National Screening Committee for the US International Fulbright Science and Technology Award, to select international Ph.D. students.

Figure 3. The PI with her students, scientists at beam line 33BM-C at APS. Dr. Brian Toby and Dr. Robert B. Von Dreele were visiting to learn about the PIs experiments and the new CIP detector. Shown in picture are (L to R) Dr. Brian Toby and Dr. Robert B. Von Dreele, Ryan P. Haggerty, Jonathan L. Bell, Dr. Paul Zschack, Dr. Pankaj Sarin, Prof. Waltraud M. Kriven, and Evgenia Karapetrova.