METHOD OF ETCHING LITHIUM METANIOBATE MONOCRYSTALS Russian patent published in 1995 - IPC

FIELD: hydrothermal etching. SUBSTANCE: method involves treatment of lithium metaniobate monocrystals at hydrothermal conditions at 150-300 C and pressure 50 atm (not less). Etching liquids are aqueous solutions of acid H₃PO₄, HNO₃ and salts MeNO₃, MeF, MeHF₂, MeHPO₄, MeH₂PO₄ where Me alkaline metal, or aqueous salt solutions MeH₂PO₄, Me₂HPO₄, MeHF₂ where Me alkaline metal, or aqueous solutions of alkali mixture MeOH and salt MeNO₃ where Me alkaline metal, or in pairs mixed aqueous solutions of salts MeNO₃,MeH₂PO₄,MeHF₂, MeF. Method ensures to etch large monocrystals with size above 2 x 10 x 10 mm (no cracking at etching), no requirement for expensive nonactive temperature-resistant materials as platinum, iridium. EFFECT: increased etching rate, decreased cost of process.