灰色框架在按钮点击的背景中 - Ionic2

Question

单击ionic2中的自定义按钮时，会出现一个灰色框，突出显示项目的边距。想要删除这个灰色框架。

HTML -

<ion-col width-33 *ngFor="let department of departments" col-no-padding>
  <ion-item class="department" no-lines text-wrap no-margin>
    <button ion-item (click)="deptSelectHandler($event, department)" detail-none no-padding> 
      <ion-avatar>
        <img  src="{{department.image.url}}" >

      </ion-avatar>
      <span>{{department.name}}</span>
     </button>
  </ion-item>
</ion-col>

CSS -

.department{
 background-color: $colorWhite;
ion-label{
   background-color: $colorWhite;
  text-align: center;
  button{
    img{
        width: 75px;
        height: 75px;
      }
      span{
        font-size: 12px;
        text-transform: capitalize;
        white-space: nowrap;
      }
  }  
}

}