The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.

A cold storage material having a large thermal capacity in a ultra-low temperature range of 10 K or less and being highly durable against thermal shock and mechanical vibration. The cold storage material contains a rare earth oxysulfide ceramic represented by the general formula R.sub.2O.sub.2S in which R is one or more kinds of rare earth elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, and Al.sub.2O.sub.3 having a specific surface area of 0.3 m.sup.2/g to 11 m.sup.2/g is added to the cold storage material.

A cold storage material having a large thermal capacity in a ultra-low temperature range of 10 K or less and being highly durable against thermal shock and mechanical vibration. The cold storage material contains a rare earth oxysulfide ceramic represented by the general formula R.sub.2O.sub.2S in which R is one or more kinds of rare earth elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, and Al.sub.2O.sub.3 having a specific surface area of 0.3 m.sup.2/g to 11 m.sup.2/g is added to the cold storage material.

A cold storage material of an embodiment includes a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and a first group element of 0.001 atom % or more and 10 atom % or less, in which a maximum value of volume specific heat in a temperature range of 2 K or more and 10 K or less is 0.5 J/(cm.sup.3.Math.K) or more.

A cold storage material of an embodiment includes a rare earth oxysulfide containing at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and a first group element of 0.001 atom % or more and 10 atom % or less, in which a maximum value of volume specific heat in a temperature range of 2 K or more and 10 K or less is 0.5 J/(cm.sup.3.Math.K) or more.

A refrigerator is provided, including rare earth cold accumulating material particles filled in a cold accumulating vessel. The rare earth cold accumulating material particles are a rare earth oxide or a rare earth oxysulfide. The rare earth cold accumulating material particles define a sintered body. An average crystal grain size of the sintered body is 0.5 to 5 μm, a porosity of the sintered body is 10 to 50 vol. %, and an average pore size of the sintered body is 0.3 to 3 μm. In an arbitrary cross-section of the rare earth cold accumulating material particles, a number of pores per a unit area of 10 μm×10 μm is 20 to 70.

A refrigerator is provided, including rare earth cold accumulating material particles filled in a cold accumulating vessel. The rare earth cold accumulating material particles are a rare earth oxide or a rare earth oxysulfide. The rare earth cold accumulating material particles define a sintered body. An average crystal grain size of the sintered body is 0.5 to 5 μm, a porosity of the sintered body is 10 to 50 vol. %, and an average pore size of the sintered body is 0.3 to 3 μm. In an arbitrary cross-section of the rare earth cold accumulating material particles, a number of pores per a unit area of 10 μm×10 μm is 20 to 70.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.