Abstract: A novel planar waveguide structure has been constructed by sintering substantially pure SiO.sub.2 layers in a He.sub.2 /BCl.sub.3 atmosphere. This results in the generation of a liquid phase of substantially lower viscosity than that of the deposited silica by itself. Since viscous sintering is enhanced by the presence of this liquid, consolidation occurs at lower temperature, e.g. 1000.degree.-1100.degree. C., than those used in the prior art, e.g. 1350.degree.-1500.degree. C. Much of the B.sub.2 O.sub.3 remains unreacted with the silica particles it helps to sinter, acting like a flux to bring about consolidation. This remaining B.sub.2 O.sub.3 is removed at the conclusion of the consolidation procedure by steam treatment at temperatures of 900.degree.-1100.degree. C. Some boron is incorporated into the silica layer, changing its CTE without substantially increasing its index.

Abstract: This invention is an acid palladium strike bath which improves adhesion and porosity of subsequent platings of palladium or palladium alloys on metal substrates, especially those susceptible to passivation such as nickel, chromium, bronze and steel. The acid palladium strike bath which is useful for both low-speed and high speed plating operation includes a complexing agent selected from organic diamines and has a pH ranging from 2.0 to 6.0, preferably from 3.7 to 4.1. When used on easily corrodable substrates, such as copper, the palladium strike deposit protects the parts from chemical attack in the subsequent mainplating bath and prevents its contamination.