Method for making metal oxide sputtering targets (barrier powder envelope)

A process for making a metal oxide sputtering target, comprising the steps of:

• providing a graphite die assembly having a die cavity with graphite walls;
• providing a first metal oxide material and a second metal oxide material;
• wherein the first metal oxide material comprises a material in powder form which is volatile and thermally unstable at the elevated temperature, and wherein the at least one layer of the second material substantially prevents a reducing gas from penetrating to the first material during the hot-pressing step,
• wherein the die cavity having a bottom, side and top wall, the process including providing a collar ring and a separator ring, depositing a layer of the second material in powder form above the bottom wall, positioning the collar ring within the side wall of the die cavity and the separator ring within the collar ring, loading the first material inside of the separator ring, removing the collar from the die cavity thereby leaving a space, depositing powder of the second material into the space, removing the separator ring from the die cavity, and depositing a top layer of the second material in powder form thereabove, the first material being thereby surrounded by a layer of the second material,
• hot-pressing the materials at an elevated temperature using the graphite die assembly to produce a metal oxide target blank.