Preparation And Study Of NM₂Si₂O₇、N₂MSi₂O₇（N=Ba,Sr;M=Zn,Mg） And Y₂Zr₂O₇ Co-doped Red-violet Pigment

Ion doping is one of the important means to realize the color development of the matrix.According to the crystal field theory,the crystal field splitting energy determines the visible light absorption wavelength of the matrix,and the splitting energy is affected by many factors.The coordination Polyhedrons have different splitting energies with changes in shape,and the distance between the central ion and the ligand ion also affect the splitting energy.For this reason,the zinc silicate and magnesium silicate,which are similar in structure to"Chinese dark blue"Ba Cu₂Si₂O₇ and"Chinese light blue"Ba₂Cu Si₂O₇,are selected as the matrix in this paper.Taking the advantage of multiple polyhedrons with different shapes in the structure,and color the matrix through the doping of Ni,then introduces the second doping element（Ba/Sr）to realize adjustment of the color,and successfully prepared a series of color products through the Sol-Gel method and the NHSG method.In view of the continuous advancement of ceramic decoration methods,especially the increasing popularity of laser printing technology,the requirements for the pigments used in laser printing are becoming more and more stringent,especially the morphology of the pigment,which plays an important role in determining the quality of decoration.Therefore,the microwave hydrothermal method was introduced,and Y₂Zr₂O₇was used as the matrix,taking the advantage of its feature that ions prone to be replaced at A-sites and B-sites.Then colored the matrix by the doping of Fe,and enhanced the doping amount through the introduction of Tb,the monodisperse spherical target product is successfully prepared at final.The main research results are as follows:（1）The precursor gel was prepared via Sol-Gel method under the conditions of a water-alcohol volume ratio of 1:2,volume ratio of glacial acetic acid and mixture of water and alcohol is 2:3,and a Si/Ba or Si/Sr molar ratio of 2.2/1.The gel was dried and milled,then heat treated for 3 hours.Ba M_2-xNi_xSi₂O₇（M=Zn,Mg）,Ba₂Zn_1-xNi_xSi₂O₇and Sr₂Mg_1-xNi_xSi₂O₇single phase products were obtained at1100℃,1200℃ and 1250℃,respectively;The L*a*b*values of red Ba Zn_1.6Ni_0.4Si₂O₇are 55.8,34.02,and 11.89,the L*a*b*values of purple-red Ba Mg_1.65Ni_0.35Si₂O₇ are 52,24.34,and-4.21,respectively,and the L*a*b*of Blue-green Ba₂Zn_0.7Ni_0.3Si₂O₇are 56.15,-10.77,and-21.26,respectively,and the L*a*b*values of the red-violet Sr₂Mg_1-xNi_xSi₂O₇are 59.73,18.71,and-28.6,respectively.（2）Fixing the doping amount of Ni,the second doping element（Sr/Ba）is introduced,with the increase doping amount of（Sr/Ba）,the color of Ba_1-xSr_xZn_1.6Ni_0.4Si₂O₇sample shifted from red to purple-blue hue,the Ba_2-xSr_xZn_0.7Ni_0.3Si₂O₇sample changes from blue-green to pink-violet,the Sr_2-xBa_xMg_0.8Ni_0.2Si₂O₇sample showed a trend that the purple hue weakened and the red hue strengthened.（3）The precursor gel was prepared via the NHSG method under the conditions of ethylene glycol to ethanol volume ratio of 3:1,glacial acetic acid to alcohol solution volume ratio of 1:4,and Si/Sr molar ratio of 2.1:1.The gel was dried and milled,then heat treatment for 3 h,SrZn_2-xNi_xSi₂O₇and Sr₂M_1-xNi_xSi₂O₇（M=Zn,Mg）single crystal phase products were obtained at 1100℃ and 1200℃,respectively.The results shows that though the NHSG did not realize the heterogeneous polymerization of atoms,while it avoided the occurrence of hard agglomeration during the drying process,and helps to reduce the synthesis temperature of Sr₂Mg_1-xNi_xSi₂O₇single crystal phase by about 50℃ compared with Sol-Gel method.（4）The L*a*b*values of the prepared blue SrZn_1.8Ni_0.2Si₂O₇are 52.38,8.61 and-42.1 respectively,as the doping amount of the second doping element Ba increases,the color of the product changes from blue to purple and shift to red finally.The L*a*b*values of the prepared purple Sr₂Zn_0.7Ni_0.3Si₂O₇were 62.15、15.06 and-17.94respectively,and the color of the product changed from pink purple to blue-green with the increase of the Ba doping amount.The Sr_2-xBa_xMg_0.7Ni_0.3Si₂O₇sample also showed a change in color that purple tone weakens and red tone strengthens with the increase of Ba doping amount.（5）The Ba is introduced as the second doping element with a doping amount of0.4 or 0.6,which enhanced the doping amount of Ni in the Sr₂MSi₂O₇（M=Zn,Mg）matrix from 0.3 to 0.5.The color intensity of Sr_2-xBa_xZn_0.5Ni_0.5Si₂O₇is higher than that of 0.3Ni single-doped product,and a*value is greatly enhanced,while the prepared Sr_2-xBa_xMg_0.5Ni_0.5Si₂O₇gets a stronger color intensity than that of 0.3Ni single-doped product only when x is 0.4,but its a*value and b*negative value both decrease.（6）The color of the product is the result of the transition of electrons from low energy d orbitals to high energy d orbitals,which is also closely related to the coordination of Ni.The color difference of Ni in each matrix and the color change during co-doping are essentially result of the combined effects of the differences in the ratio of Ni in different coordination,and the difference of wavenumber related to orbital transitions.Also a number of fitting curves of Ni doping amount and N₂M_1-xNi_xSi₂O₇product color coordinates are established,which is convenient for intuitively obtaining the color performance of corresponding products through calculation.The XRD refinement of part N₂M_1-xNi_xSi₂O₇show that Ni did enter the unit cell and caused the decrease of unit cell volume,but the unit cell volume did not continue to decrease with the increase of Ni doping,indicating that within the range of Ni doping for the preparation of single phase product,multiple structural units of the crystal are spontaneously adjusted.（7）In the study of preparing Fe-Tb co-doped Y₂Zr₂O₇by hydrothermal method,it was found that the urea is introduced as the precipitant,the molar ratio of urea to cations is fixed at 100:1,the volume ratio of n-propanol to water in the composite solvent is determined to be 3:1,the hydrothermal system is determined to be 150℃ for 3 hours,a monodisperse spherical product with a particle size of about 1μm is obtained,and PVP used as a surfactant is more conducive to the dispersion of the particles.The co-doped Tb ions increase the upper limit of Fe doping in the matrix by means of equilibrium valence.