Abstract: A bead string of tin oxide crystallite or a bead string of complex oxide crystallite of tin oxide and titanium oxide contains tantalum and has specific hue as well as a crystallite size on the order of nanometer, and exhibits excellent conductivity and improves the catalytic activity. A bead string includes a tin oxide crystal particle aggregate or a crystal particle aggregate of a complex oxide of tin oxide and titanium oxide, in which the crystal particle aggregate contains at least one particle having a crystallite size of 5 to 50 nm, and when the crystal particle aggregate is pressed under a pressure of 0.1 MPa to have a thickness of 1 cm, in the color of the resultant particle aggregate represented by Lab color space, a lightness L* value is 80 or less, a chromaticity a* value is ?4 or less, and a chromaticity b* is ?3 or less.

Abstract: A support powder can improve cell performance under high humidity environment. A support and metal catalyst, including: a support powder; and metal fine particles supported on the support powder; wherein: the support powder is an aggregate of support fine particles; the support fine particles are fine particles of oxide compound and has a chained portion structured by a plurality of crystallites being fusion bonded to form a chain; the crystallites have a size of 10 to 30 nm; the support powder has a void; the void includes a secondary pore having a pore diameter of more than 25 nm and 80 nm or less determined by BJH method; and a volume of the secondary pore per unit volume of the support fine particles structuring the support powder is 0.313 cm3/cm3 or more, is provided.

Abstract: A support and metal catalyst with improved electric conductivity is provided. A support and metal catalyst, including: a support powder; and metal fine particles supported on the support powder; wherein: the support powder is an aggregate of support fine particles; the support fine particles have a chained portion structured by a plurality of crystallites being fusion bonded to form a chain; the support fine particles are structured with metal oxide; and the metal oxide is doped with a dopant element, and an atomic ratio of titanium with respect to total of titanium and tin is 0.30 to 0.80, is provided.

Abstract: A support powder can improve cell performance under high humidity environment. A support and metal catalyst, including: a support powder; and metal fine particles supported on the support powder; wherein: the support powder is an aggregate of support fine particles; the support fine particles are fine particles of oxide compound and has a chained portion structured by a plurality of crystallites being fusion bonded to form a chain; the crystallites have a size of 10 to 30 nm; the support powder has a void; the void includes a secondary pore having a pore diameter of more than 25 nm and 80 nm or less determined by BJH method; and a volume of the secondary pore per unit volume of the support fine particles structuring the support powder is 0.313 cm3/cm3 or more, is provided.