UTF-8 will be supported from TC10.1
When your database was created with an older TC Version it is not so easy to switch the database to UTF-8.
As far as I know is the offical way to setup a new Teamcenter environment with UTF-8 and transfer the existing data by a Multi-Site.
You're using Windows or Unix/Linux?
Starting with Teamcenter 11.2 supports the Unicode UTF-8 character set on Windows.