| 主权项 |
1. Process for the preparation of a bulk or thin-film single-crystal formed of a matrix of a cubic sesquioxide of scandium, yttrium and/or rare earth metal, said matrix being doped or not doped with at least one element of the series of the lanthanides, said single-crystal corresponding to the following formula (I):
(R11-xR2x)2O3 (I) in which:
R1 is at least one metal with a valency of III chosen from scandium, yttrium and the elements of the series of the lanthanides;x is such that 0≦x<1;R2 represents at least one element chosen from the series of the lanthanides; said process being carried out in a chemically inert crucible and comprising the following stages: 1) preparing a pulverulent mixture (PM1) comprising at least:
a solute composed of at least one sesquioxide of following formula (IIa): R′12O3 (IIa), in which R′1 represents the same element as R1, and, when said matrix is doped with at least one element of the series of the lanthanides, of at least one sesquioxide of following formula (IIb): R′22O3 (IIb), in which R′2 represents the same element as R2, in a molar percentage (xmp) such that 0<xmp≦25 mol %, it being understood that said sesquioxide of formula (IIa) is then present within said solute in a molar percentage 100-xmp, said solute being present within the mixture PM1 in an amount z such that 0<z≦93 mol %,a primary solvent composed of a mechanical mixture of a compound of following formula (III):
[Li6(R″11-x″R″2x′)(BO3)3] (III)in which R″1 and R″2 respectively represent the same element as R1 and R2 and x′ is such that 0≦x′<1;
2) preparing a pulverulent mixture PM2 comprising said solute and a synthesis solvent of following formula (IV):
[Li6(R″11-x′, R″2x′)(BO3)3]+(Li2O and/or B2O3 and/or LiX) (IV)in which R″1 and R″2 respectively represent the same element as R1 and R2, x′ is such that 0≦x′<1, and X=F, Cl, Br or I, by addition to the mixture PM1 of at least one pulverulent additive chosen from Li2O, B2O3 and LiX with X=F, Cl, Br or I, said mixture PM1 being present within the mixture PM2 in an amount z′ such that 15≦z′<100 mol %, said additive being present within the mixture MP2 in a total molar amount s such that 0<s≦85 mol %, and s=100-z′ in the mixture PM2; the molar amount z″ of the solute within the mixture PM2 being such that z″=z·z′;
3) bringing the pulverulent mixture PM2 obtained above in stage 2) to a temperature TPM2 at least equal to the melting point (TM.p.) of said mixture PM2 and ≦1250° C., in order to bring about the dissolution of the solute in the synthesis solvent of formula (IV) and to obtain a liquid solution of said solute in the synthesis solvent of formula (IV); 4) maintaining the temperature of the liquid solution at the temperature TPM2 for a period of time of at least 6 hours, with stirring by means of a solid support subjected to rotation around a vertical axis; 5) cooling, in controlled fashion, the liquid solution from the temperature TPM2 down to a temperature TExp between the saturation temperature (TSat) of the liquid solution and the critical supersaturation temperature (CTSuper) of the liquid solution or the temperature of solidification of the liquid solution, in order to bring about the controlled crystallization of the expected sesquioxide of formula (I) on said solid support immersed in said liquid solution and subjected to rotation around a vertical axis, said cooling being carried out at a maximum rate of 1° C.·h−1; 6) withdrawing the solid support from the liquid solution and then cooling, in controlled fashion, the sesquioxide of formula (I) crystallized on the solid support from the temperature TExp down to ambient temperature, at a maximum rate of 50° C.·h−1. |
