Ceramic capacitors and dielectric compositions

Claim 2

A dielectric composition comprising non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate.

Claim 3

A composition as claimed in claim 1 comprising between 50 and 80 wt % non-stoichiometric lead magnesium niobate, between 10 and 35 wt % non-stoichiometric lead zinc niobate and between 5 and 30 wt % non-stoichiometric lead iron niobate.

Claim 4

A composition as claimed in claim 2 further including up to 10 wt % lead oxide (PbO).

Claim 5

A composition as claimed in claim 3 comprising 60 wt % lead magnesium niobate, 35 wt % lead zinc niobate, 5 wt % lead iron niobate and 4 wt % lead oxide.

Claim 6

A dielectric composition as claimed in claim 1 and whose constituents are in the proportions indicated in one of the mix examples quoted in Table 1.

Claim 7

A ceramic capacitor including dielectric fired at a temperature between 900° and 1040° C. and comprising non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate.

Claim 8

A ceramic capacitor including dielectric fired at a temperature between 900° and 1040° C. and comprising non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate.

Claim 9

A ceramic capacitor as claimed in claim 6, the dielectric including up to 10 wt % lead oxide.

Claim 10

A ceramic capacitor as claimed in claim 6 and including high silver content internal electrodes fired with the dielectric.

Claim 13

A method as claimed in claim 9 and including the step of calcining the mixture at approximately 650° C. prior to firing.

Claim 14

A dielectric composition made by a method as claimed in claim 10 and in accordance with one of the possibilities quoted in Table 3.

Claim 17

A method as claimed in claim 12 and including the step of further calcining the mixture following addition of the PbO.

Claim 18

A dielectric composition made by a method as claimed in claim 12 and in accordance with one of the possibilities quoted in Table 4.

Claim 19

A multilayer ceramic capacitor including a dielectric composition comprising 65 wt % non-stoichiometric lead magnesium niobate, 27.5 wt % non-stoichiometric lead zinc niobate and 7.5 wt % non-stoichiometric lead iron niobate, manufactured by a method comprising preparing each of said three complex niobates separately, mixing the separately prepared niobates, calcining the mixture, forming a plurality of dielectric sheets from the calcined mixture, screen-printing a plurality of electrodes onto each of a plurality of dielectric sheets, assembling a stack of the resultant screen-printed sheets, pressing the stack together, dividing the stack into individual capacitor components and firing the individual components at the conditions specified in Table 2.

Claim 20

A multilayer ceramic capacitor including a dielectric composition comprising 65 wt % non-stoichiometric lead magnesium niobate, 27.5 wt % non-stoichiometric lead zinc niobate and 7.5 wt % non-stoichiometric lead iron niobate, manufactured by a method comprising preparing each of said three complex niobates separately, mixing the separately prepared niobates, calcining the mixture, forming a plurality of dielectric sheets from the calcined mixture, screen-printing a plurality of electrodes onto each of a plurality of dielectric sheets, assembling a stack of the resultant screen-printed sheets, pressing the stack together, dividing the stack into individual capacitor components and firing the individual components at the conditions specified in Table 2.