Add　some　K2O　mineralizer　to　SiC　kiln　furniture　bonded　with　fine　silicon　powder　can　help　α-cristobalite　whose　bulk　effect　is　large　convert　to　α-trydymite　whose　bulk　effect　is　small.　Its　mineralizing　ability　is　almost　the　same　as　MnO2[1],　but　its　price　is　cheaper　and　it　can　be　got　more　easier,　then　its　pratical　value　is　higher　than　MnO2.　The　crystal　structure　and　amount　was　investigated　with　XRD　technique.　By　discussing　the　influence　of　crystal　structure　to　the　kiln　furniture　properties,　we　know　the　best　proportion　for　K2O　to　be　added　is　1.5%.