Using percolation to design ZnO composites with hBN modified grain boundaries to obtain varistor-like behavior
Michael W. Mervosh,
Sevag Momjian,
Javier Mena-Garcia,
Clive A. Randall
Affiliations
Michael W. Mervosh
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA; Materials Research Institute, Millenium Science Complex, University Park, PA, 16802, USA; Corresponding author at: N-244, Millennium Science Complex, University Park, PA, 16802, USA
Sevag Momjian
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA; Materials Research Institute, Millenium Science Complex, University Park, PA, 16802, USA
Javier Mena-Garcia
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA; Materials Research Institute, Millenium Science Complex, University Park, PA, 16802, USA
Clive A. Randall
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA; Materials Research Institute, Millenium Science Complex, University Park, PA, 16802, USA
Conventional varistors rely on the formation of a Double Schottky Barrier within the intergranular region of ZnO via acceptor doping and a Bi2O3 phase. This work has been able to yield varistor-like behavior via cold sintered ZnO composites by placing 2D hBN flakes on the grain boundaries within the ZnO matrix. Above the percolation threshold, a network of resistive hBN barriers is formed which prevents current from flowing through the more conductive ZnO. However, at a given voltage, electrons can tunnel through the hBN if the layers are kept thin enough. Within this narrow band of hBN content, samples have been fabricated with α values as high as 9.5. The composite system demonstrated Schottky conduction at low fields before switching to Fowler-Nordheim tunneling at high fields. This microstructural design was able to show greater nonlinearity compared to previous attempts at creating varistor materials through the unique cold sintering process (CSP).
