lookup field

Hi all,

I have lookup field as shown below

Phase pipeline is my entity. I have to default Phase pipeline field. I write below code for achieving this defaulting but it is not working. 

function paymentMethodRequired_onchange() {

var lookup = new Array();
lookup[0] = new Object();
lookup[0].value = "10";
Xrm.Page.getAttribute("aw_pipelinephase").setValue(lookup);

}

It is giving me undefined value instead of 10 as shown below

This lookup contain these values

What can I do to achieve this task?

Thank you