Abstract: Separator materials for secondary lithium batteries comprising as the base material a vinylidene fluoride-hexafluoropropylene (VdF-HFP) copolymer resin, wherein polymer particles having a higher softening point than the copolymer are blended and dispersed in the separator. As the polymer particles, fluorinated polymer particles are preferable. The separator materials for secondary lithium batteries are free from short-circuiting during the step of the heat lamination of the separator on electrode membranes.

Abstract: A Gunn diode in which the conversion efficiency can be improved without lowering the reliability, by reducing the dead zone while maintaining n.sup.+ nn.sup.+ structure. In this Gunn diode, the donor impurity concentration in the n-type active layer is graded along a direction perpendicular to a contact plane between the n-type active layer and the n.sup.+ -type layers, and an average concentration gradient of the donor impurity concentration in the n-type active layer simultaneously satisfies the following two inequalities: G>(A.sub.1 N/L)exp(-NL/S.sub.1) and G<(A.sub.2 N/L)exp(-NL/S.sub.2), where L is a thickness of the n-type active layer, N is an average concentration of the donor impurity, S.sub.1 =0.87.times.10.sup.12 cm.sup.-2 is a constant, S.sub.2 =1.32.times.10.sup.12 cm.sup.-2 is a constant, A.sub.1 =2.0 is a constant, and A.sub.2 =9.0 is a constant.