Conductive sintered oxide, thermistor element including the same, and temperature sensor including the same

A conductive sintered oxide which comprises:

• a conductive crystal phase having a perovskite structure represented by (RE1-cSrc)MdO3, in which
• RE is a group of elements consisting of Yb and/or Lu and at least one element selected from Group IIIA excluding Yb, Lu and La and
• M is a group of elements consisting of Al and at least one element Selected from Groups IVA, VA, VIA, VITA and VIII,
• a first insulating crystal phase represented by RE2O3, in which RE is as defined above, and
• a second insulating crystal phase represented by SrAl2O4, wherein
• the conductive crystal phase has a coefficient c which satisfies 0.18<c<0.50,
• the conductive crystal phase has a coefficient d satisfying 0.67≦d≦0.93, the coefficient d indicating a ratio between an amount of the element group (RE1-cSrc) constituting A sites and the amount of the element group M constituting B sites of the conductive crystal phase, and
• a content of a third insulating crystal phase represented by RE4Al2O9, the content of the third insulating crystal phase represented by RE4Al2O9 not including zero, is smaller than the content of the first insulating crystal phase and is smaller than the content of the second insulating crystal phase.