ELECTROCHEMICAL REACTION SINGLE CELL AND ELECTROCHEMICAL REACTION CELL STACK

To suppress concentration of stress at a specific location in an interface between an electrolyte layer and an adjacent layer (e.g., an air electrode and an intermediate layer).SOLUTION: An electrochemical reaction single cell includes an electrolyte layer and an air electrode and a fuel electrode opposed to each other in a first direction across the electrolyte layer. In the electrochemical reaction single cell, when viewed in a specific section of at least one section along the first direction, a surface of particles located between two adjacent grain boundary points at an interface on an air electrode side of the electrolyte layer is located within a range of ±0.2 μm or less in a direction orthogonal to a virtual straight line with respect to the virtual straight line connecting the two adjacent grain boundary points.SELECTED DRAWING: Figure 6 【課題】電解質層と、それに隣接する層（例えば空気極や中間層）との界面において特定箇所に応力が集中することを抑制すること。【解決手段】電気化学反応単セルは、電解質層と、電解質層を挟んで第１の方向に互いに対向する空気極および燃料極と、を備える。電気化学反応単セルにおいて、第１の方向に沿った少なくとも１つの断面である特定断面で見たときに、電解質層のうち、空気極側の界面において、互いに隣り合う２つの粒界点の間に位置する粒子の表面は、隣り合う２つの粒界点を結ぶ仮想直線に対して当該仮想直線と直交する方向に±０．２μｍ以下の範囲内に位置する。【選択図】図６