Sintered material, connection structure, composite particle, joining composition, and method for manufacturing sintered material

A sintered material comprising

• 1) a base portion, the base portion being a metal sintered body,
• 2) one or more buffer portions, and
• 3) one or more filling portions,
• wherein the one or more buffer portions and the one or more filling portions are dispersed in the base portion,
• wherein each of the one or more buffer portions is formed from at least one of a pore and a material that is not the same as that of the metal sintered body,
• wherein each of the one or more filling portions is formed from at least one of particles and fibers,
• wherein the sintered material has a value of A that is 0.2 or more,
• wherein A is a kurtosis of volume distribution of the base portion in a three-dimensional image of an entirety of the sintered material,
• wherein each of the one or more filling portions is formed from a composite having a structure in which a colloid catalyst or a sintering accelerator is placed on base particles,
• wherein the base particles are resin particles or organic-inorganic hybrid particles,
• wherein the base particles have a 10% K value of 10 N/mm2 or more and 3000 N/mm2 or less, and
• wherein the base particles have a coefficient of variation (CV value) of the particle diameter of 40% or less, and
• wherein each of the one or more filing portions is present so that a part or all of the surface thereof is in contact with the base portion through chemical bonding.