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Dr Dan Baker

PhD Research

Investigation of the structures and physical properties of novel lead-free niobates for piezoelectric applications. The main focus of the PhD is on potassium sodium niobate (KxNa1-xNbO3), both as a stand-alone material and in solid solutions with other perovskite structures, such as LiTaO3, LiSbO3 and BaTiO3. KNN is of particular interest because of its high piezoelectric response and the proposed presence of several morphotropic phase boundaries.

Techniques

  • X-ray Diffraction: used to determine the crystal structure and lattice parameters of the materials. Data taken on the group's Panalytical X'Pert Pro MPD with Anton Paar furnace attachment.
  • Neutron Scattering: also used to determine crystal structure, particularly oxygen positions. Powder diffraction as a function of temperature will be carried out for selected compositions at ISIS, UK, and ILL, Grenoble.
  • Impedance Analyser: for measurements of the dielectric susceptibility of samples at various temperatures.
  • NMR : examines the local environments of atoms in the samples. This technique will compliment the X-ray/neutron scattering of general structure, to examine the local structure, and how it changes in the presence of a morphotropic phase boundary. The active nuclei that will be studied include 23Na, 39K, 93Nb and 17O (enriched samples). All measurements will be performed on the solid-state NMR spectrometers at Warwick, with magnetic fields ranging from 4.7 - 14.1 T.
  • Rietveld Refinement: Topas Academic is used to perform Pawley and rietveld refinement to determine structure, composition and thermal parameters of materials. Charge flipping will also be implemented when single crystals are available.
  • Single Crystal Growth: Attempts are underway to produce single crystal specimens of KNN at the various morphotropic phase boundaries using the flux method. Currently small single crystals have been grown with compositions from x = 0.1 to x = 0.4.
  • Single Crystal diffraction: Scans of single crystals taken with Oxford diffraction Gemini CCD diffractometer, with data analysed using Crysalis Pro and Shelx software.

 

Conferences and Workshops

 10/06
 Edinburgh  PCG meeting  
 01/07  Durham  PCG Rietveld Workshop  
 02/07  Liberec
Piezoelectricity for end users III
 Workshop also attended
 04/07   Leicester
 Condensed Matter and Materials Physics  Talk given on KNN phase diagram
 08/07  Marrakech  European Crystallography Meeting  Poster presented on KNN tilt system and new high temperature phase
 09/07  Oxford  10th Oxford School on Neutron Scattering

 

 08/08  Osaka  IUCr conference 2008  Poster presented on single crystal and powder work of KNN
09/10 Warsaw E-MRS Fall meeting 2010 Oral presentation on MPBs in lead-free piezoelectrics

        

 Experiments

 09/06 ISIS, UK  HRPD/GEM   Phase diagram mapping of KNN
 10/07 ILL, France
D2B  Low temperature scans and MPB analysis of KNN


Published Papers

Structural study of KxNa1-xNbO3 (KNN) for compositions in the range x = 0.24 - 0.36, D. W. Baker, P. A. Thomas, N. Zhang & A. M. Glazer, Acta Cryst. (2009). B65, 22-28

A comprehensive study of the phase diagram of KxNa1-xNbO3, D. W. Baker, P. A. Thomas, N. Zhang & A. M. Glazer, Appl. Phys. Lett. (2009). 95, 091903

Structures of K0.05Na0.95NbO3 (50-300 K) and K0.30Na0.70NbO3 (100-200 K), N. Zhang, A. M. Glazer, D. Baker & P. A. Thomas, Acta Cryst. (2009). B65, 291-299

 

Supervisors

My supervisors for the PhD are Prof. Pam Thomas (Crystallography) and Prof. Mark Smith (NMR). 

Dan Baker

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