A study is made of fracture from cyclic loading of WC spheres on the top surfaces of thick (1 mm) brittle layers on polymeric substrates, as representative of repetitive occlusal contact on dental crown structures. The advantage of glass layers is that internal cracks can be followed in situ during the entire cyclic loading process. The glass surfaces are first given a surface-abrasion treatment to control the flaw state, such that the strengths match those of dental porcelains. Cyclic contact tests are carried out at prescribed maximum loads and frequencies, in water. In addition to conventional cone cracks that form outside the contact circle, additional, inner cone cracks form within the contact in the water environment. These inner cones are observed only in cyclic loading in water and are accelerated at higher frequencies, indicating a strong mechanical driving force. They tend to initiate after the outer cones, but subsequently catch up and penetrate much more rapidly and deeply, ultimately intersecting the underlying coating/substrate interface. Comparative tests on glass/polymer bilayers versus monolithic glass, in cyclic versus static loading, in water versus air environment, on abraded versus etched surfaces, and with glass instead of WC indenters, confirm the existence of a dominant mechanical element in the inner-cone crack evolution. It is suggested that the source of the mechanical driving force is hydraulic pressure from intrusion and entrapment of liquid in surface fissures at the closing contact interface. This new type of cone cracking may limit dental crown veneer lifetimes under occlusal fatigue conditions, especially in thicker layers, where competing modes-such as undersurface radial cracks-are suppressed.

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High dielectric constant (k) CaCu3Ti4O12 (CCTO) has been studied as a potential filler for low‐temperature cofired ceramics (LTCC) based on typical calcium aluminoborosilicate glass. CCTO does not appear to be chemically reactive with the glass regardless of the firing temperature over the compositional range of 30–90 wt% CCTO. Dielectric constant and dielectric loss turned out to depend strongly on the relative content of CCTO and firing temperature. As an optimal composition, the glass with 60 wt% CCTO exhibited a k∼32 and tan δ∼0.01 as a result of firing at 850°C, which is preferably applicable for the medium k LTCC applications. The higher content of 90 wt% CCTO needed to be densified at 900°C for better densification with a higher dielectric constant of ∼150. However, the 900°C firing was not acceptable for the 30 and 60 wt% CCTO‐containing samples due to the unexpected expansion of samples leading to significantly enlarged pores.

BaTiO 3 -based dielectrics containing the selective additive combinations from Pb-free glasses and fluoride compounds such as AlF 3 , BaF 2 , CaF 2 , LiF and ZnF 2 were studied mainly for a potential N 2 -fireable embedded capacitor in printed circuit board with Cu metallization. The physical and dielectric properties, such as dielectric constant (k), loss tangent (tanδ) and T c , strongly depended on the choice of additive combination. A bismuth borosilicate glass was most promising in terms of the degree of densification and dielectric constant. The samples containing LiF and ZnF 2 and sintered at 950°C looked most beneficial in that these additives produced high k of >1,200 and low tanδ of < 0.022 at room temperature regardless of sintering atmosphere. As an example, the 95BaTiO 3 -2LiF-3(Bi borosilicate) sample exhibited k~1,340 and tanδ0.022 at room temperature when fired at 950°C in N 2 .