The Study On Preparation And Color Development Mechanism Of Rare Earth Oxide Doped Zirconia Ceramics

Colored ceramics have been widely used in the fields of restorative dental restoration materials,decoration industry and mobile smart phone terminals based on its good biocompatibility,excellent metallic luster,and good mechanical properties.Since modern times,with the concept of energy conservation and environmental protection gaining popularity,people's requirements for colored ceramics colorants have gradually increased,and raw materials must have the characteristics of non-toxic,pollution-free and low energy consumption.For further research,inorganic colorants gradually replaced organic and sulfide colorants.In addition to traditional white and yellow color ceramics,domestic and foreign scholars have gradually developed various color materials such as black,blue,red,pink and green,which have greatly enriched the color ceramic color system.Secondly,research on dyeing of color ceramics has gradually turned to internal coloring,and related optical properties and color rendering mechanisms,electrical properties,magnetic properties,and mechanical properties have also been studied.This article mainly researched red,black and blue zirconia ceramics,and received a series of environmentally friendly,low energy consumption and excellent performance colored zirconia ceramics.Traditional Fe-doped red zirconia ceramics have poor color saturation.The redness values?a*?below 20,yellow-blueness values?b*is about 20?,and poor fracture toughness(5.0-6.0 MPa·m^1/2).Secondly,CdS_1-xSe_x-doped red zirconia ceramics have poor color stability,colorants are toxic,and their redness value can reach 50.However,their thermal stability is poor and carcinogenic,and the preparation process is complicated and difficult?cladding method?.In this paper,a new type of colorant was selected,the nontoxic and harmless rare earth oxide CeO₂ was used as the red colorant.The high temperature reduction method was used to prepare red zirconia ceramics,and a new type of red zirconia ceramics with good color saturation was obtained.The redness value?a*?exceeded 30 and the yellow and blueness values?b*?approached 0.Secondly,the thermal stability was improved,and toughness exceeded 9.0 MPa·m^1/2.The composition of traditional colorants of black zirconia ceramics is usually complex oxides,and these oxides contain Co.During the sintering process of black zirconia ceramics,these composite Co-spinels interact with each other,resulting in poor phase stability of black zirconia ceramics.It is difficult to present a single phase of t-ZrO₂,and further volume expansion and contraction occur,which causes the matrix to be easily cracked and difficult to form.In addition,the use of Co-doped colorants increases costs greatly and is not conducive to large-scale mechanized production.Secondly,the preparation process is a dyeing method,which has a negative impact on the mechanical properties of the black zirconia ceramics,and the obtained black zirconia ceramics are uneven in color and easy to fade.In this study,titanium oxide?TiO₂?was used as the black colorant,which greatly reduced the cost of raw materials.The high temperature reduction method was used to prepare a new type of bright black zirconia ceramic.The brightness?L*?of the Ti-doped black zirconia ceramics is about 40,and the a*and b*values are about 0,which indicates that the ceramic is bright black.CoAl₂O₄ spinel was widely used in the pigment and ceramics colorant for its brilliant color and good color stability.Cobalt-aluminum spinel doped zirconia ceramics has a long history of application.Scholars have conducted a series of in-depth studies on blue zirconia ceramic colorants and preparation processes.The generous use of Co-doped pigments has brought huge energy consumption and costs,and research has gradually turned to the development of blue zirconia ceramics with low cobalt content.However,as the cobalt content decreased,the color of the blue zirconia ceramic changed from dark blue to light blue.Therefore,it is imminent to develop a blue zirconia ceramic with low cobalt content,excellent mechanical properties,and high color saturation.This experiment represents an improvement over traditional blue zirconia ceramics.A series of blue zirconia ceramics with continuously adjustable colors and excellent mechanical properties have been prepared by changing the Co/Al content and the amount of additive in the colorant.Compared with the existing blue zirconia ceramics on the market,the amount of pigment added has been reduced from 30.0%to 2.5%,the blueness values are similar,both are about 30,and the fracture toughness is increased from 6.0-7.0 MPa·m^1/2 to 7.5-10.5 MPa·m^1/2.The color development mechanism of color zirconia ceramics has always been a hot topic in the industry.The main theories include color center theory,ionic color theory,and multiphase color theory.Based on the analysis of the results of this experiment,the color development of Ce-doped YSZ red zirconia ceramics and Ti-doped YSZ black zirconia ceramics can be attributed to color center theory,and the color development of blue zirconia ceramics can be attributed to multiphase color theory.