The　work　reported　in　paper　concerns　the　use　of　diatomite　to　form-stabilise　sodium　nitrate,　a　phase　change　material　(PCM)　for　medium　temperature　thermal　energy　storage　applications.　The　composite　was　found　to　be　able　to　retain　up　to　70%　of　the　nitrate　salt.　X-ray　diffraction　(XRD)　analyses　suggested　an　excellent　chemical　compatibility　between　diatomite　and　the　salt.　Scanning　electron　microscope　(SEM)　analyses　demonstrated　an　even　distribution　of　the　salt　within　the　diatomite　structure.　Differential　scanning　calorimetry　(DSC)　measurements　showed　that　melting　temperature　of　the　material　was　approximately　307.8　degrees　C　with　a　latent　heat　of　115.79　kJ/kg.　Mechanical　characterization　of　the　composite　material　showed　a　compressive　strength　of　the　composite　materials　as　high　as　22.17　MPa.　The　composite　materials　were　found　to　have　a　fairly　low　thermal　conductivity　of　similar　to　0.5　W/m　K　and　an　addition　of　graphite　could　give　a　substantial　thermal　conductivity　enhancement　(similar　to　6-fold　with　an　additional　of　10　wt%　graphite).　(C)　2017　Elsevier　Ltd.　All　rights　reserved.