A 
thermal barrier coating (TBC) top coat which is a high entropy 
oxide (HEO) having a high configurational entropy, contains at least 5 different 
oxide-forming metallic cations, is a 
single phase or single crystalline structure, such as tetragonal or cubic over unexpectedly wide temperature ranges up to and beyond top coat operating temperatures of preferably at least 2300 DEG F. The TBC top coats exhibit low 
thermal conductivity, good 
sintering resistance, excellent 
phase stability and good thermal 
cycling performance. At least five of the different 
oxide-forming metallic cations include: a) at least one of the transition metals: Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Ni, Cu, or Zn, and / or at least one of the lanthanides La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb. Dy, Ho, Er, Yb, or Lu. One of the at least five different oxide-forming metallic cations may also comprise at least one of the alkaline-earth metals: Be, Mg, Ca, Sr, or Ba.