Cryogenic ceramic and apparatus

Ceramic material:

• (a) Characterized by
• (1) being a dielectric insulator and
• (2) having values of specific heat at selected temperatures below 15.degree. K. that are greater than or at least equal to the values of specific heat of pure Pb at those same temperatures, and
• (b) consisting essentially of a crystalline phase with a composition defined by the molar formula AB.sub.2 O.sub.4 wherein
• A is Cd ion alone or in combination with one or more of other divalent metal ions where at least about 90 mole % of A is Cd ion, and
• B is Cr ion plus other trivalent metal ion or ions where at least about 90 mole % of B is Cr ion.

Ceramic material:

• (a) characterized by
• (1) being a dielectric insulator and
• (2) having values of specific heat at selected temperatures below 15.degree. K. that are greater than or at least equal to the values of specific heat of pure Pb at those same temperatures, and
• (b) consisting essentially of
• (1) a crystalline phase with a composition defined by the molar formula AB.sub.2 O.sub.4 where
• A is selected from one or more of Group 2b metal ions alone or in combination with one or more of other divalent metal ions where at least about 90 mole % of A is Group 2b metal ion or ions, and
• B is either Cr ion or Cr ion plus one or more of other trivalent metal ions where at least about 90 mole % of B is Cr ion, and
• (2) a mineralizer crystalline phase that is of the niobite type.

In cryogenic refrigeration apparatus comprising a load to be refrigerated,

• a refrigerant adapted to refrigerate the load at temperatures below 15.degree. K.,
• thermal energy absorbing elements associated with the refrigerant and adapted to function at temperatures below 15.degree. K.,
• wherein the improvement comprises at least one of the thermal energy absorbing elements being composed of ceramic material:
• (a) characterized by
• (1) being a dielectric insulator and
• (2) having values of specific heat at selected temperatures below 15.degree. K. that are greater than or at least equal to the values of specific heat of pure Pb at those sampe temperatures, and p2 (b) consisting essentially of a crystalline phase with a composition defined by the molar formula AB.sub.2 O.sub.4 where
• A is selected from one or more of Group 2b metal ions alone or in combination with one or more of other divalent metal ions where at least about 90 mole % of A is Group 2b metal ion or ions, and
• B is either Cr ion or Cr ion plus one or more of other trivalent metal ions where at least about 90 mole % of B is Cr ion.