Poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) is an aromatic polyester with molecular structure similar to that of poly(ethylene terephthalate)(PET). In this paper, the space charge storage ability and its stabil...Poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) is an aromatic polyester with molecular structure similar to that of poly(ethylene terephthalate)(PET). In this paper, the space charge storage ability and its stability in corona charged PEN were studied by measurement of surface potential decay under different storage conditions including dif- ferent temperatures and relative humidities, and analysis of open circuit thermally stimu- lated discharge (TSD) current spectra and charge TSD curves. The comparison between the charge stability of PEN and PET was carried out. The results point out that the charge stability of PEN is markedly better than that of PET under different environmental condi- tions. By means of isothermal depolarization program, the space charge lifetimes (effec- tive time constant) τ at room temperature of positively and negatively charged PEN are estimated to be 90 y. The results offer theoretical and technical support for the use of PEN as the chip of high quality electret condenser microphone due to its excellent dielectric, mechanical and thermal properties.展开更多
The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on ...The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3 substrates,has excited an immediate surge of research interest.To explore an alternative physical path instead of chemical reduction to realizing superconductivity in this compound,using pulsed laser deposition,we systematically fabricated 63 Nd0.8Sr0.2NiOx(NSNO)thin films at a wide range of oxygen partial pressures on various oxide substrates.Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples.With the oxygen content reducing in the NSNO films by lowering the deposition oxygen pressure,the NSNO films are getting more resistive and finally become insulating.Furthermore,we tried to cap a 20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a high oxygen pressure of 20 Pa to create oxygen vacancies on its surface and did not succeed in obtaining higher conductivity either.Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd0.8Sr0.2NiO2 crystals suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO3 heterostructures.However,SrTiO3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well,which may thus partially contribute to conductivity.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.50503018)the Volkswagen Foundation(Grant No.I/77365).
文摘Poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) is an aromatic polyester with molecular structure similar to that of poly(ethylene terephthalate)(PET). In this paper, the space charge storage ability and its stability in corona charged PEN were studied by measurement of surface potential decay under different storage conditions including dif- ferent temperatures and relative humidities, and analysis of open circuit thermally stimu- lated discharge (TSD) current spectra and charge TSD curves. The comparison between the charge stability of PEN and PET was carried out. The results point out that the charge stability of PEN is markedly better than that of PET under different environmental condi- tions. By means of isothermal depolarization program, the space charge lifetimes (effec- tive time constant) τ at room temperature of positively and negatively charged PEN are estimated to be 90 y. The results offer theoretical and technical support for the use of PEN as the chip of high quality electret condenser microphone due to its excellent dielectric, mechanical and thermal properties.
基金financially supported from the National Natural Science Foundation of China(Nos.51822101,51861135104,51771009 and 11704018)
文摘The recently reported 9-15 K superconductivity in Nd0.8Sr0.2NiO2/SrTi03 heterostructures that were fabricated by a soft-chemical topotactic reduction approach based on precursor Nd0.8Sr0.2NiO3 thin films deposited on SrTiO3 substrates,has excited an immediate surge of research interest.To explore an alternative physical path instead of chemical reduction to realizing superconductivity in this compound,using pulsed laser deposition,we systematically fabricated 63 Nd0.8Sr0.2NiOx(NSNO)thin films at a wide range of oxygen partial pressures on various oxide substrates.Transport measurements did not find any signature of superconductivity in all the 63 thin-film samples.With the oxygen content reducing in the NSNO films by lowering the deposition oxygen pressure,the NSNO films are getting more resistive and finally become insulating.Furthermore,we tried to cap a 20-nm-thick amorphous LaAlO3 layer on a Nd0.8Sr0.2NiO3 thin film deposited at a high oxygen pressure of 20 Pa to create oxygen vacancies on its surface and did not succeed in obtaining higher conductivity either.Our experimental results together with the recent report on the absence of superconductivity in synthesized bulk Nd0.8Sr0.2NiO2 crystals suggest that the chemical reduction approach could be unique for yielding superconductivity in NSNO/SrTiO3 heterostructures.However,SrTiO3 substrates could be reduced to generate oxygen vacancies during the chemical reduction process as well,which may thus partially contribute to conductivity.
