Barium, strontium, and calcium as getters in electron tubes

Abstract

Strontium and calcium getters have possible use replacing barium as gas sorbers in color picture tubes and other electron tubes. Stable getters were made of a calcium–aluminum or strontium–aluminum alloy, which was powdered, mixed with nickel powder, and pressed into a ring‐shaped channel of stainless steel. After exhaust pumping and tip‐off of the picture tube, the getter was heated to form a gas‐sorbing film of strontium or calcium, which was deposited by evaporation onto the internal surfaces of the picture tube. Strontium and calcium getters were evaluated and compared to barium getters in color picture tubes by the oxygen sorbtion test, which determined the maximum oxygen quantity that can be absorbed by the film without damage to the tube’s oxide cathode. When flashed in 25‐in. color tubes, barium and strontium showed the same oxygen capacity, both initially and after 11 and 25 weeks of life test. When flashed in tubes of smaller size and surface area, strontium showed lower oxygen capacity than barium, a result indicating slower bulk diffusion of oxygen through thick films of strontium oxide than through barium oxide. Calcium showed satisfactory gettering speed allowing normal tube operation out to 25 weeks of life test; however its gettering capacity was lower, being about 1/4 that of barium and indicating even slower diffusion of oxygen in calcium oxide than in strontium oxide.