ExportTo-CSV does not work properly in PS - powershell

Question

I'm in the end of creating a simple PS script.
It basically take specific AD user, check which users are directly reports to him and filter these users by prefix EXT then it listing Expiration Date of account and name of these accounts.
I found it difficult to Import these data to CSV file.
Yes, it works but results are more far that what I expect. I should get file filled with Account Names and expiration date of these accounts, instead I got only this:
results
Here is my script
$external_users_data = #{}
$if_ext_user = Get-AdUser -Identity xxxx.xxxx -Properties DirectReports | Select -ExpandProperty DirectReports
ForEach ($user in $if_ext_user)
{
$U = Get-AdUser -identity $user -Property *
if ($U.UserPrincipalName -like 'EXT.*'){
Write-Output $U.UserPrincipalName
Write-Output $U.AccountExpirationDate
<#$user_object = #{
AccountName = $U.UserPrincipalName
ExpirationDate = $U.AccountExpirationDate
}#>
$external_users_data.add($U.UserPrincipalName,$U.AccountExpirationDate)}}
Write-Host $external_users_data
[ExtAccount_expiration_dates]#{AccountName = $U.UserPrincipalName; ExpirationDate = $U.AccountExpirationDate} |Export-Csv -Append -Path 'C:xxxxxxxxx/csv'
for security reasons, I blurred sensitive lines with name of account and file path.
Any ideas are much appreciated.
I'm expecting that final CSV file will be filled with proper data like AccountName and ExpirationDate of that account.

Answer 1

PSCustomObject available from PS V3.0 or newer. You can use it for better results. For more info please refer PSCustomObject Doc
I have no environment to test this code. So, please test it from your end. Hope it works.
$users = Get-AdUser -Identity xxxx.xxxx -Properties DirectReports | Select-Object -ExpandProperty DirectReports
$external_users_data = ForEach ($user in $users) {
$U = Get-AdUser -identity $user -Property *
if ($U.UserPrincipalName -like 'EXT.*') {
[PSCustomObject]#{
"AccountName" = $U.UserPrincipalName
"ExpirationDate" = $U.AccountExpirationDate
}
}
}
$external_users_data | Export-Csv -Append -Path 'C:xxxxxxxxx/csv'