Sinter Of Alumina Ceramic And Preparation Of Y Dopping Cubic HfO₂

The features of Hafnium are high melting point, high dielectric constant and high absorption of high-energy radiation. So the research of preparation of ceramic scintillators containing hafnium compounds or hafnium has been becoming more and more popular. Y2O3 and HfO2 can form cubic phase solid solution. Featured with high density and high atomic number, this solid solution has a strong absorption coefficient of X-ray radiation. According to these advantages, they can be widely used in the scintillation applications. Al2O3 is one of the most important engineering ceramics with high melting point, high chemical stability and high hardness. The mechanical electrical and optical properties of Al2O3 enable a wide range of usage in many fields. However, the strong ionic bond of it leads to a low diffusion coefficient, and high sintering temperature. It is an urgent need for alumina ceramic industry to solve the problem that alumina ceramic must be obtained at a lower sintering temperature.At first, high pure HfClO2, Y(NO3) 3, Eu(NO3) 3 were used as raw material. A.R.grade glycine and urea were used as fuel. The red nanoscale scintillator Y2Hf7O17::Eu powders with pure cubic phase can be successfully prepared via nitrate solution combustion method at 800℃for 2 hours. The red scintillator Y2Hf7O17::Eu nanopowders were also prepared by solid state at high temperature at 1600℃, and the PL intensities with two methods were compared. The emission spectra and excitation spectra were studied to get the optimal Eu3+ content. We found that we can gain the better performance of luminicience by combustion in lower temperature. Depending of the temperature, Hafnia exits in three phases:monoclinic phase, tetragonal phase and cubic phase. Only the monoclinic phase of HfO2 is stable at low temperatures. The cubic phase is the optimal phase as ceramic scinillators. It is found that Y doping in HfO2 would increase the stability of the cubic phase relative to the monoclinic phase by reducing the energy difference and the phase transition pressure. The optimal Y3+ content were determined. Then replace Y3+ by Eu3+, Optimal ration of Y3+ and Eu3+ can be found by measuring the Luminous intensity. The PL intensities with different calcined temperatures were compared.Then, starting from high purityγ-alumina and seed crystal (a-Al2O3) TiO2 was used as impurities to reduce the sintering temperature. The SEM data, sintering cure and density were analyzed, comparing to the result of that starting from a-Al2O3 and TiO2. The effect that the weight content of seed crystal and TiO2 to sintering character and microstructure of alumina ceramics is studied. We found that sintering alumina ceramic was influenced by the size and the quantity of the seed crystal.So we determine that the best sintering process.