to center a button in an ionic application, you simply use this code
<ion-buttons text-center>
<button ion-button
type="submit">Submit</button>
</ion-buttons>
if you only use the <button> tag alone, , it will not work. you have to wrap it in a <ion-buttons>
tag, for example, the following examples will not center a button
<button ion-button
text-center
type="submit">Submit</button>
https://www.webune.com/forums/how-to-ionic-2-how-to-center-form-button-in-the-middle.html