We have studied some novel synthesi

We have studied some novel synthesis approach, such as solvothermal synthesis, ionthermal synthesis, synthetic method at low-heating temperatures. So far, three methods have been used to synthesise HEOs, namely solid-state reaction, wet chemical, and epitaxial growth. The wet chemical methods used for synthesizing HEOs include nebulised spray pyrolysis, flame spray pyrolysis and reverse co-precipitation. The third HEC synthesis routine is epitaxial growth of films. So far in the literature only pulsed laser deposition (PLD) has been used to prepare HEOs. However, the cost-effective and large-scale synthesis of high-purity and small-size HEOs is still difficult. Therefore, it is still a challenge for the scientific community to develop an advanced method to prepare HEOs at low temperature.