DURABILITY IMPROVEMENT OF AG-BASED LOW-EMISSIVITY COATINGS

The durability of magnetron sputtered low-emissivity (Low-E) coatings composed of a silver (Ag) layer sandwiched between two layers of zinc oxide was investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The degradation after a humidity test at 50 degrees C, 95% relative humidity for 144 h was caused by the destruction of the top ZnO layer. It was found that sputtered ZnO films had a large internal stress and the stress was greatly reduced by the addition of a small amount of aluminium to a ZnO target or by sputtering at higher pressures. The durability of Ag-based Low-E coatings was greatly improved by reducing the internal stress of the top oxide layers.