Thermal conductivity features of ZnO-based varistors using the laser-pulse method

An efficient and accurate framework for calculating lattice thermal conductivity of solids: AFLOW—AAPL Automatic Anharmonic Phonon Library

“…Wurtzite zinc oxide (ZnO) is another well-characterized system. Olorunyolemi et al 91 and Barrado et al 92 reported κ ' of polycrystalline ZnO with an average particle size of 20 and 1000 nm, respectively. AAPL, performed with average grain size of 500 nm, is in very good agreement with the experimental results capturing the effects of the grain boundaries' scattering (Fig.…”

Importance of the Hubbard correction on the thermal conductivity calculation of strongly correlated materials: a case study of ZnO

“…The calculated thermal conductivity using PBE and PBE+U (calculation with exclusion of isotope scattering in parentheses) are summarized in Table 3 along with a recent LDA calculation9 and experimental data obtained through SThM812 and laser flash method71011 at 300 K. We found that while PBE, which resulted in thermal conductivities of 39 and 60 W/mK, along the a- and c-axes, respectively, agrees well with LDA9, PBE+U resulted in values of 57 and 87 W/mK, and even higher, 63 and 95 W/mK, when not including the effects of isotope scattering. In all cases, however, the calculated thermal conductivity in the c-axis direction was roughly 50% greater than in the a-axis direction.…”

“…Unfortunately, reported measurements of the thermal conductivity of ZnO are widely inconsistent, varying from as low as 38 W/mK7 to as high as 116 W/mK8. A recent calculation9 showed minor agreement with lower experimental data from laser flash measurements on unknown sample conditions71011 leading the authors to thus question other higher experimental values obtained by scanning thermal microscopy (SThM)812 along known crystallographic directions of a perfect single crystal. The utilization of a traditional density functional theory (DFT) exchange-correlation functional in their study is, however, questionable.…”

Non-uniform ageing behavior of individual grain boundaries in ZnO varistor ceramics

“…Tel: +86 10 62775585; fax: +86 10 62784709. individual grain boundaries in microstructure scale, which is the origin of the nonlinear electrical properties for ZnO varistor ceramics. [14][15][16][17][18][19] Up to now, several methods have been adopted to probe the electrical behavior of individual grain boundaries in ZnO varistors. [20][21][22][23][24][25][26][27] Van Kemenade and Eijnthoven measured the breakdown voltages on more than 500 grain boundaries by evaporating Au microelectrodes on the surface of ZnO samples and proposed that the average barrier voltage of single grain boundaries is around 3.6 V as the current through the grain boundary is 1 A.…”