Conductive target material

Abstract

The present invention relates to a conductive target material comprising essentially one lithium compound, preferably lithium phosphate, and carbon, and also typical impurities. The invention further relates to a process for producing a conductive target material and to the use thereof.

Claims

1. A conductive target material, consisting of: lithium phosphate (Li.sub.3PO.sub.4), wherein said lithium phosphate (Li.sub.3PO.sub.4) assumes a proportion of greater than or equal to 80% by area on a cut surface of total area of a single conductive target material; carbon occurring predominantly with a proportion of greater than 99% of the carbon being graphite and has a proportion of said carbon between 3 and 20 at %; and lithium carbonate (Li.sub.2CO.sub.3); wherein the lithium phosphate (Li.sub.3PO.sub.4) and the carbon form a biphasic microstructure, with the lithium carbonate (Li.sub.2CO.sub.3) being present in a small proportion that is not regarded as a further phase in relation to the biphasic microstructure; and typical impurities to form said single conductive target material for the deposition of a lithium ion electrolyte layer by a DC or pulsed DC sputtering process, wherein said single conductive target material has a relative density of at least 95%.

2. The conductive target material according to claim 1, wherein said single conductive target material comprises said carbon occurring predominantly with a proportion of greater than 90% being at least one carbon cluster that percolates from one side of said single conductive target material to an opposite side of said single conductive target material.

3. The conductive target material according to claim 1, wherein said single conductive target material has an electrical conductivity of at least 0.01 S/mm.

4. The conductive target material according to claim 1, wherein said single conductive target material has a thermal diffusivity of at least 2.5 mm.sup.2/s.

5. The conductive target material according to claim 1, wherein said single conductive target material has a coefficient of thermal expansion of between 10 and 20 ppm/K.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 Microstructure of an inventive conductive target material, light microscope image. This shows: regions rich in essentially one lithium compound, in this case lithium phosphate-rich regions 1, regions of elemental carbon 2, and a portion of a percolating carbon cluster 3 corresponding to the image section

(2) FIG. 2 Phase determination by means of x-ray diffraction (XRD) of an inventive conductive target material (JCPDS cards used: Li.sub.3PO.sub.4: 00-015-0760; carbon (graphite) 00-023-0064; Li.sub.2CO.sub.3: 00-022-1141)

(3) FIG. 3 Conductivity [S/mm] vs. content of carbon introduced [at %] in an inventive target material

(4) FIG. 4 Comparison of deposition rate and power input for the inventive conductive target material with the prior art

DESCRIPTION OF THE INVENTION

Working Examples

Example 1

(5) Lithium phosphate powder having a volume-weighted average particle size of 3.64 μm (D50=3.09 μm, D90=6.81 μm) was mixed with 5 at % of carbon powder having a volume flow weighted average particle size of 3.88 μm (D50=3.49 μm, D90=6.81 μm) in a Turbula mixer for 30 minutes. The powder mixture thus obtained was introduced into the graphite mould of a hot press and compacted therein at a temperature of 875° C. and a pressing force of about 3 MPa under an Ar atmosphere for 2 h to give a target material having the dimensions 261×241 mm and thickness 10 mm. The target material thus obtained was cleaned by means of sandblasting and subsequently processed under dry conditions to the final geometry. By means of a step of bonding to a copper backplate, a finished target was produced.

Example 2

(6) Lithium phosphate powder having a volume-weighted average particle size of 3.64 μm (D50=3.09 μm, D90=6.81 μm) was mixed with 10 at % of carbon powder having a volume flow weighted average particle size of 3.88 μm (D50=3.49 μm, D90=6.81 μm) in a Turbula mixer for 30 minutes. The powder mixture thus obtained was introduced into the graphite mould of a spark plasma sintering (SPS) system and compacted therein under a pressure of 20 bar and at a temperature of 875° C., which was maintained over the course of 1 h, to give a disc-shaped target material having a diameter of 73.5 mm and a thickness of 5 mm. The target material thus obtained was subsequently ground to a finish by means of a dry processing step and processed by means of a step of bonding to a copper backplate to give a finished target.

Example 3

(7) A target composed of an inventive conductive target material, produced analogously to Ex. 1 and 2, comprising lithium phosphate and carbon (10 at %), was used to ascertain the deposition rate by conducting a DC sputtering experiment under an Ar atmosphere (pressure 7.5*10.sup.−3 mbar) at a power input of 10 W/cm.sup.2 of target material. Within a period of 990 s, a layer thickness of 1.5 μm was achieved. A measurement of the electrical conductivity of this layer by means of four-point measurement did not give a measurable conductivity.