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We report on the softening properties and viscosity of glasses from the system ZnO–Na2O–SO3–P2O5 for low‐temperature sealing applications. Up to a ratio of network‐forming ions PO43−:SO42− of about 2:1, a gradual substitution of P2O5 by SO3 results in decreasing glass transition and softening temperatures. At the same time, decreasing kinetic fragility is observed, noteworthy even for decreasing the total amount of network former from 44 at.% to 39 at.%. Thermomechanical and calorimetric analyses reveal a distinct SO42−‐promoted relaxation phenomenon at temperatures significantly below the macroscopic glass transition temperature, which is interpreted as a result of the formation of an increasingly interconnected assembly of SO42− and PO43− units with increasing SO3 content.

We report on the direct consequences of reversible water adsorption on the optical performance of silica-based nanoporous antireflective (AR) coatings as they are applied on glass in photovoltaic and solar thermal energy conversion systems. In situ UV-VIS transmission spectroscopy and path length measurements through high-resolution interferometric microscopy were conducted on model films during exposure to different levels of humidity and temperature. We show that water adsorption in the pores of the film results in a notable increase of the effective refractive index of the coating. As a consequence, the AR effect is strongly reduced. The temperature regime in which the major part of the water can be driven-out rapidly lies in the range of 55°C and 135°C. Such thermal desorption was found to increase the overall transmission of a coated glass by ~ 1%-point. As the activation energy of isothermal desorption, we find a value of about 18 kJ/mol. Within the experimental range of our data, the sorption and desorption process is fully reversible, resulting in optical breathing of the film. Nanoporous AR films with closed pore structure or high hydrophobicity may be of advantage for maintaining AR performance under air exposure.