Advances in Electroluminescent Devices with Barium Titanate Particles By Antoine Dumont, Sylvie morin CAP Congress 2017, Queen’s University

Objectives Synthesis of BaTiO3 nanoparticles of a controlled size and structure for an electric permittivity study in an electroluminescent device (ELD). (Professor Sylvie Morin, collaboration with W. J. Pietro, York University) Analysis of the effect of lanthanum doping in barium titanate and optimization of the concentration for our application.

Presentation Overview Barium titanate particles - Synthesis - Characterization Electroluminescent devices - Experimental techniques - Permittivity and Luminescence results

Barium Titanate BaTiO3 has applications in multilayer ceramic capacitors, infrared detectors and thermistors Lattice structure 1 Ba (apex of lattice) 1 Ti (center of lattice) 3 O (face-centered) High dielectric materials are of great interest for developments in nanotechnology.

Barium Titanate c c a c a a Proposed core-shell structure for particles of around 100nm a c Tetragonal Cubic a c a c Smaller Particles Bigger Particles Aoyagi S. et al, JTAC, 81 (2005) Wada S. et al, Journal of App. Physics, 42 (2003)

Particles Synthesis : Sol-Gel Method Process : - Bonding of metal with organic precursor M(OR)n - Hydrolysis by adding water solution M(OH)n - Condensation by adding base MOn - Thermal treatment Advantages : control of size & low temperature Strong bonds M-O-M-O-(...), only break above 1000°C Samples created with 0.0, 0.3, 0.5 and 0.7mol% lanthanum concentration

Characterization of Particles SEM images Experimental particles Commercial powder 100 nm 400 nm 1 μm

Characterization of Particles X-ray diffraction Identification of BaTiO3 crystal structure Rietveld analysis: Peaks between tetragonal and cubic Possible core-shell structure suggested in literature

Characterization of Particles Induced coupled Plasma Atomic Emission Spectroscopy 0.3%La 0.5%La 0.7%La http://www.chemiasoft.com/chemd/node/52

Electroluminescent Device Design 19mm Bottom view 20mm 19mm ZnS BaTiO3 Ag Top view Silver Silver Silver BaTiO3 2mm ZnS ITO coated Plastic Conductive Non-conductive

Electroluminescent Device Support

Electroluminescent Device Whole device 0.3 mm thick, including plastic. All layers are inks (epoxy, particles, solidifier)

Impedance Analysis Impedance Spectroscopy Studying the system’s behaviour (Leaking Resistance, Capacitance) with a varying current Nyquist Plot : Imaginary part of impedance Z as a function of the real part. Equivalent circuit for our devices : And the circuit’s impedance :

Impedance Analysis Impedance measured from 500Hz to 10 000Hz Blue : Exp. Data Red : Sim. Data

Electroluminescent Device Result 0.5% La doped BaTiO3 material showed a minimum of 20% superior permittivity compared to all our other samples, expected behavior* BatiO3 Sample with 0.5% La doping showed extraordinary emission of light - Anomaly among other samples but is a real result - Leaking resistance 32% lower than similar devices! Com 0.0% La 0.3%La 0.5%La 0.7%La * Vijatovic Petrovic M.M. et al, Mat. Char., 62 (2011) Beltran H. et al, J. Am. Ceram. Soc., 87 (2005)

Electroluminescent Device Result New BaTiO3 synthesis to try to reproduce the result… without success (14 new samples) Confirmation of 0.5% La concentration superiority over the next best (0.7%) 0.5% La 0.7% La

Electroluminescence Efficiency Trend among samples : ELD’s efficiency seems to have a reverse proportionality with the leaking resistance of the dielectric, after a threshold limit. I∝ 1 𝑅 ??? Not a typical focus for advances in this field but could introduce a new way to improve the energy efficiency.

Conclusion Significant improvement of luminescence for BaTiO3 based electroluminescent devices Possible colossal increase of luminescence under the right leaking resistance conditions Upcoming work : Collaboration for use of industrial printer for precise thickness and resistance-controlled device fabrication

Acknowledgment Support and collaboration with colleagues in Sylvie Morin’s group Funding :

Screen-printing apparatus