dart – Flutter transition on border

I’ve a TextField and when i focus to enter border is altering straight. However i need make it smoother. How am i able to make it ?

Container(ornament: isFocused ? focusedBorder : blurBorder) //isFocused triggers when i focus to enter.

and my borders :

 remaining focusedBorder = BoxDecoration(
      borderRadius: BorderRadius.round(8),
      gradient: LinearGradient(
          start: Alignment.centerLeft,
          finish: Alignment.centerRight,
          colours: [
            Color.fromARGB(255, 141, 56, 211),
            Color.fromARGB(255, 156, 90, 209),
            Color.fromARGB(255, 93, 53, 213),
          ],
          stops: [
            0.0,
            0.5,
            0.7
          ]));
  remaining blurBorder = BoxDecoration(
      borderRadius: BorderRadius.round(8),
      border:
          Border.all(width: 1.5, colour: Colour.fromARGB(255, 238, 241, 246)));