Effect of Temperature Control Gradient and Time on the Quality of Synthetic Jadeite

Synthetic jadeite is grown from quantitatively proportioned amorphous powder in a high-pressure high-temperature (HPHT) environment. The growing environment greatly impacts the quality of the synthetic jadeite. In this paper, before applying the traditional HPHT growing stage, we added different low-temperature growing stages and investigated the effect of the low-temperature growing stage on the quality of the synthetic jadeite. The pressure of all growing environments was fixed to 4.5 GPa. Using 100 mesh powder prepared by high-temperature solid-state method, we compared the quality of the synthetic jadeites that both grown in high-temcperature(1 100 ℃ and 1 400 ℃) environments with 180 mins preservation time, but have different low-temperature and presenation time (950 ℃, 10 mins and 1 100 ℃, 30 mins). Using 140 mesh powder prepared by high-temperature solid-state method and sol-gel method, we compared the quality of synthetic jadeites that both grown in a high-temperature of 1 100 ℃ with 180 mins preservation time, but have different low-temperature preservation times at a fixed low-temperature of 950 ℃. The results showed that the synthetic jadeite grown in different environments were all polycrystalline and with uniform green colour, and their gemmological properties, UV-Vis absorption spectra and FTIR reflection spectra were consistent with those of natural jadeite. The microslice images of the synthetic jadeite showed that all the synthetic jadeite had a granular-columnar structure. The scanning electron microscope (SEM) images showed that the synthetic jadeite developed long needle-like non-directional crystals and smaller grain gaps with adding low-temperature preservation stages(1 100 ℃, 30 mins), and the longer the low-temperature preservation stage, the smaller the grain gap would be. In conclusion, synthetic jadeite with better quality could be obtained by adding a low-temperature preservation stage in the process of growing synthetic jadeite.