<v-icon> vuetify材质图标（mdi）在vuetify和nuxt应用程序中显示问题？

我正在使用nuxt和vuetify。所有标签都工作正常。但是当我使用时<v-icon>，该图标没有显示..

<v-flex xs12 mb-3>
<v-btn outline fab small color="blue-grey lighten-4">
    <v-icon color="grey darken-4">mdi-facebook</v-icon>
</v-btn>

<v-btn outline fab small color="blue-grey lighten-4">
    <v-icon color="grey darken-4">mdi-google-plus</v-icon>
</v-btn>

<v-btn outline fab small color="blue-grey lighten-4">
   <v-icon color="grey darken-4">mdi-linkedin</v-icon>
</v-btn>
</v-flex>