as a Microwave Dielectric Resonator," J . Am. Ceram. Soc., 58 19-10] 418-20 (1975). 'S. Kawashima, M. Nishida, I. Ueda, and H. Ouchi, "Dielectnc Properties of Ba(Zn,,,Nb2,,)0,-Ba(Zn ,,3Ta,,)0, Ceramics at Microwave Frequency": pp. 293-96 in ,)O, Ceramics with Temperature-Stable High Dielectric Constant and Low Microwave Loss," Jpn. J. Appl. Phys., 21 [lo] L624-26 (1982). Sodium depth profiles were determined in water-leached glass samples with molar composition 20Na20 * lORO *xA1203* (70x)Si02 (RO = CaO, MgO, and ZnO) using secondary ion mass spectrometry. The leaching of sodium ions decreases with increasing Alz03 content in all three glass systems. For x = 0 the leaching is hardly affected by the nature of the divalent cation. For x = 5 and 10 the corrosion resistance is highest for the glass containing ZnO, and for the glasses containing ZnO and MgO, respectively. These glasses correspond to those with the smallest fraction of NBOs. From all these results it is concluded that the nonbridging oxygen atoms play an important role in promoting the leaching of a glass.Presented as part of the Woldemar A. Weyl Award Lecture during the 13th Inter-
