Ion Concentration and Stress in a Chemically Tempered Glass

Abstract

samples were also magnetized to saturation with no resultant change in impedance. IV. ConclusionsThe study of the electrical properties of high-density irondeficient nickel-zinc ferrites has led to the conclusions that:(1) The dc resistivity for iron-deficient nickel-zinc ferrites sintered to 99.9% of theoretical density is similar for compositions between Nf.~Zllo.wFel.oo04-and Nio.40Zllo.51Fel.oo04-.(2) For dense Nio.a,Zllo.oaFel.soOa-: (a) Room temperature resistivity varies with sintering temperature from 3 X 10' n-cm at llOO°C to 2x10' n-cm at 1220°C; ( b ) temperature dependence of resistivity is equivalent in air and in oxygen from 25" to 700°C for the test conditions described and is insensitive to changes in grain size between 6 and 15 pm; (c) activation energy for conduction is approximately 0.57 eV; and ( d ) densification proceeds rapidly to 2 99% of the theoretical density for sintering temperatures 2 1170°C; the room temperature resistivity for these specimens increases to an equilibrium value with sintering time by bulk cation diffusion. Samples sintered at lower temperatures require long sintering periods to attain equivalent densification, and the room temperature resistivity is invariant with sintering time and corresponding porosity.( 3 ) The Seebeck coefficient for the ferrites studied is 550 pV/"C from 200" to 700°C.(4) The dielectric constant, E', for the p-type ferrites varies from 17.3 at 0.5 MHz to 16.4 at 15 MHz. AcknowledgmentsThe writers thank M. Schwartz of IBM's Components Division and T. Pohl and A. Mullaly of San Jose Systems Development Division for technical assistance.Diffusion and stress profiles were determined in an Na-for-Li exchanged LiZ0-AI,O,-Si0, glass as a function of the time of reheating in air. Comparison of the two sets of data by a thermal-stress analogy gave a fair correlation, although the depth of the compressive layer was overestimated by about 16%. Stress data alone were used to obtain an interdiffusion coefficient at 400°C which agreed well with the diffusivity obtained directly. The stress and concentration fractions were related graphically; the relation suggests that there is a slight accommodation of the larger ion by the glass structure without stress buildup during the early stages of exchange. These results led to a method of predicting the modulus of rupture of an exchanged glass after it is reheated in air.

Mechanical–Structural Investigation of Chemical Strengthening Aluminosilicate Glass through Introducing Phosphorus Pentoxide

“…The maximum hardness in the studied glass is up to 5.9 GPa. The increment in hardness is mainly attributed to the formation of surface compression through ion exchange, and the hardness decreases afterward is because of the structural relaxation (Garfinkel and King, 1970;Donald, 1989).…”

Prediction of stress profiles in ion exchanged glasses

“…Initially, stress profiles were calculated from the concentration change without considering the stress relaxation effect. Garfinkel and King [6] and Tyagi and Varshneya [7] calculated the stress profile in ion exchanged glass using the analogy with thermal stresses. The calculated stress profile was found to be much higher than the measured profile [7].…”

“…Stress profiles in single-step ion exchanged glasses have been studied by many researchers in the past several decades [6][7][8][9][10][11][12]. Initially, stress profiles were calculated from the concentration change without considering the stress relaxation effect.…”

Gradient scattered light method for non-destructive stress profile determination in chemically strengthened glass

“…The two opposite surfaces of the glass sample that were perpendicular to the light propagation direction were ground and polished off to remove the layers that could influence the measurement result. It is also possible to leave those surfaces un-strengthened by coating them with a thin film of tin oxide-antimony (a method developed by Mochel [18] and used by Garfinkel and King [19]) to block ion exchange process. Applying transmission photoelasticity to measure the stress profile can only be possible if the sample is prepared as described or cut.…”