An accepter-doped "hard" PZT is used in a piezoelectric print head instead of the conventional "soft" donor-doped material. The print head preferably is of a chevron side-shooter configuration and is advantageous for high-definition grey-scale printing....http://www.google.com.au/patents/US6619788?utm_source=gb-gplus-sharePatent US6619788 - Droplet deposition apparatus
