Si3N4　ceramics　have　shown　promising　application　prospects　as　the　sealing　materials　for　liquid　metal　batteries　(LMBs).　However,　the　joining　of　Si3N4　to　the　metal　shell　of　LMBs　is　rather　difficult　because　of　the　non-wetting　property　and　mismatch　of　their　thermal　expansion　coefficients　(CTEs).　Herein,　to　solve　the　above　issue,　W/Si3N4　functionally　graded　materials　(FGMs)　were　designed　and　fabricated　via　the　spark　plasma　sintering　(SPS)　process.　The　effects　of　layer　numbers　and　layer　components　on　the　phase　composition,　structure,　and　thermal　stress　of　the　FGMs　were　systematically　investigated　using　both　experimental　and　simulation　methods.　W/Si3N4　FGMs,　with　optimal　layer　numbers,　were　then　utilized　for　fabricating　symmetrical　W/Si3N4/W　FGMs.　The　thermal　stress　of　the　products　can　be　effectively　reduced　by　adjusting　the　MgO　content　of　the　central　Si3N4　layer.　As　a　result,　the　optimal　product　displayed　good　interface　bonding　between　two　adjacent　layers　and　also　exhibited　high　flexural　strength　(943.9　MPa)　and　electrical　resistivity　(2.0　×　1012　Ω　cm).　This　route　for　the　fabrication　of　symmetrical　W/Si3N4/W　FGMs　exhibits　the　advantage　of　high　efficiency,　and　the　products　with　excellent　properties　can　be　used　as　sealing　materials　for　LMBs.　©　2021　Elsevier　B.V.