Current Interests

Dr Mark Stewart is a Senior Research Scientist in the Functional Materials Group at NPL. His area of expertise covers the characterization of functional materials in particular piezoelectric materials. Current projects include methods to assess the efficiency of piezoelectric energy harvesters, and using laser heating as a probe for piezoelectric activity.

Biography

Mark received his BEng degree in Metallurgy and Materials Science and a PhD on diffusion in nickel-based superalloys from the University of Liverpool. He joined the Ceramics and Hardmetals Group in the Materials Division at NPL in 1986 and specialised in characterization methods for functional materials. He has worked on the development of many different test methods for characterizing materials including an automated scanning hardness indenter, a method of powder sizing using thermo gravimetric analysis, fracture strength of multilayer capacitors.

More recently in the piezoelectric materials area, he has developed polarisation loop test systems (PE loop) and advised customers on installing these test methods in house, such as at the XMAS beamline at ESRF, and beamline I11 at Diamond.

He also has a wide experience of measuring the strain output of piezoelectric materials, using techniques such as interferometry, laser triangulation, fiber optics, capacitance and strain gauges.

Selected Publications

• Spatial Characterization of Piezoelectric Materials Using the Scanning Laser Intensity Modulation Method (LIMM)
  M. Stewart and M. G. Cain
  Journal of the American Ceramic Society,91 (7), pages 2176–2181 (2008)
• Properties of morphotropic phase boundary Pb(Mg1/3Nb2/3)O3–PbTiO3 films with submicrometre range thickness on Si-based substrates
  M. Algueró, M. Stewart, M. G. Cain, P. Ramos, J. Ricote and M. L. Calzada
  Journal of Physics D: Applied Physics, 43 (20) 205401 (2010)
• Ferroelectric Hysteresis Analysis and Measurement
  M. Stewart, M. Cain and D. Hall
  NPL report CMMT(A152)
• Charge Redistribution in Piezoelectric Energy Harvesters
  M. Stewart, P. M. Weaver and M. G. Cain
  Submitted to Applied Physics Letters

Contact details

E-mail: mark.stewart@npl.co.uk
Tel: 020 8943 8524