Compounds　with　an　A(2)B(2)O(7)-type　pyrochlore　structure　have　been　identified　as　a　class　of　materials　with　low　thermal　conductivity.　To　ascertain　the　effect　of　the　pyrochlore　structure,　the　thermophysical　properties　of　rare-earth　stannates　which　constitute　the　longest　iso-structural　series　with　this　unique　crystal　structure　were　measured　and　the　thermal　conduction　behavior　was　investigated　by　analyzing　the　variation　in　the　inverse　phonon　mean　free　path　with　temperature　in　terms　of　the　phonon-scattering　theory.　The　results　show　that　the　contraction　of　rare-earth　ions　and　the　accompanying　deviation　from　the　ideal　pyrochlore　structure　result　in　a　simultaneous　increase　in　the　Young＇s　modulus　and　the　thermal　expansion　coefficient.　Scattering　due　to　the　strain　field　fluctuation　caused　by　the　systemic　displacement　of　48f　oxygen　ions　rather　than　scattering　from　the　so-called　8a　site　＂oxygen　vacancies＂　and　thermal　defects　predominates　in　reducing　the　phonon　mean　free　path　and　consequently　the　thermal　conductivity　at　relative　low　temperature.　At　a　certain　critical　temperature,　the　thermal　conduction　behavior　of　the　stannates　undergoes　a　transition　to　a　minimum　phonon　mean　free　path　mechanism,　which　is　responsible　for　the　remarkable　variation　in　temperature　dependence　of　thermal　conductivity　across　the　compositions.　(C)　2012　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.