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.
- 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
|01/07||Durham||PCG Rietveld Workshop|
||Piezoelectricity for end users III
||Workshop also attended|
||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|
|09/06||ISIS, UK||HRPD/GEM|| Phase diagram mapping of KNN
||D2B||Low temperature scans and MPB analysis of KNN
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