The new triphasic potassium−substituted hydroxyapatite (KHAP), β−tricalcium phosphate (β−TCP), and calcium pyrophosphate (CPP) proportions using easy sol−gel method were synthesized. The prepared powders was characterized by X–ray diffraction (XRD), Fourier transform infrared (FTIR), Differential thermal behavior (DTA) analysis, Energy Dispersive X–ray Analysis (EDXA), and Brunauer–Emmett–Teller (BET). In addition, the size of nano particle and micro–strain of the synthesized samples using Williamson–Hall (W–H) plots and transmission electron microscopy (TEM) were measured. The (K+Ca)/(P+C) molar ratio in the KHAP samples was around 1.67. Actually, the incorporation of potassium in the calcium deficient apatites was accompanied by the formation of mentioned triphasic mixture ceramics, upon calcination from 400 to 600 °C. However, increasing of the firing temperature to 700 °C resulted in growth of the HAP content as the dominant phase. The XRD peaks of these prepared nano−structures show same pattern with pure HAP phase with hexagonal structure and P63/m space group. Moreover, the evaluated particle size of synthesized samples by W–H and TEM methods are in good agreement as 25–95 nm. Surface area of calcined KHAP samples at 400 to 700 °C were found as 127.83, 48.39, 12.91, and 5.32 m2 g−1, respectively.