Glass ceramic materials having controllable temperature coefficients of dielectric constant
OwnerWilliam N. Lawlessinventor
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Abstract
Glass ceramic materials having controllable temperature coefficients of dielectric constant or capacitance (TCC) are provided. The ceramic component of the composition possesses paraelectric properties at least over the temperature range of -55.degree. C. to 125.degree. C. and can be controllably crystallized from the glassy matrix initially formed. Heat treatment of the glass produces crystallization of the ceramic component and results in glass ceramic materials with controlled TCC values which are useful as capacitors, resonators, microwave substrates, and the like because of their low dielectric loss characteristics and temperature stability.
Claims11
A glass-ceramic composition having a controllable temperature coefficient of capacitance and which exhibits low dielectric losses at very high frequencies, wherein the crystal content thereof is 50% or more by weight of a compound having paraelectric properties at least over the temperature range of -55.degree. to 125.degree. C., selected from the group consisting of SrTiO.sub.3 and KTaO.sub.3 and wherein the change in dielectric constant of said glass-ceramic material over the temperature range of -55.degree. to 125.degree. is less than .+-.2%.
A process of forming a glass-ceramic composition having a predetermined value of temperature coefficient of capacitance in the range of from 200 ppm/.degree.C. to -400 ppm/.degree.C. over the temperature range of -55 to 125.degree. C. comprising the steps of, mixing together 50% or more by weight of (1) a ceramic compound having paraelectric properties at least over the temperature range of -55.degree.to 125.degree. C., selected from the group consisting of SrTiO.sub.3 and KTaO.sub.3 and which can be controllably crystallized from a glassy matrix and (2) one or more glass-forming compounds, heating the mixture until a glass is formed, quenching the glass melt to solidify it, then reheating the glass to a temperature at which crystallization of the ceramic compound in the glass occurs, and maintaining said temperature for a time sufficient for said predetermined value of temperature coefficient of capacitance to be attained.
In an electrical device which includes a dielectric material, the improvement comprising, as the dielectric material a glass-ceramic compositions having a temperature coefficient of capacitance in the range of from 200 ppm/.degree.C. to -400 ppm/.degree.C. over the temperature range of -55 to 125.degree. C. and which exhibits low dielectric losses at very high frequencies, wherein the crystal content thereof is 50% or more by weight of a compound having paraelectric properties at least over the temperature range of -55.degree. to 125.degree. C. and selected from the group consisting of SrTiO.sub.3 and KTaO.sub.3.
Dependencies are inferred from the claim text.