NOVELTY - A solid electrolyte material comprises gadolinium doped-lanthanum silicate hydroxyapatite compound (I).    USE - Solid electrolyte material.    ADVANTAGE - The solid electrolyte material can be prepared simply, and consumes low energy, and has uniform quality, high purity and high electrical conductivity at low temperature of 450-750 degrees C.    DETAILED DESCRIPTION - A solid electrolyte material comprises gadolinium doped-lanthanum silicate hydroxyapatite compound (La10-xGdxSi6O27), where x is 0-6. An INDEPENDENT CLAIM is also included for a method for preparing the gadolinium doped P-type silicon hydroxyapatite acid lanthanum solid electrolyte material, which involves weighing lanthanum nitrate hexahydrate, gadolinium nitrate and tetraethyl orthosilicate in molar ratio of 10-x:x:6, adding lanthanum nitrate hexahydrate and gadolinium nitrate to anhydrous alcohol, distilled water and acetic acid to obtain mixed solution, stirring the mixture till the mixture becomes transparent, regulating pH value at 1-4 with concentrated nitric acid and ammonium hydroxide, transferring the mixture to 1-4 bottles, placing the bottles in water bath at 70-85 degrees C, stirring the mixture uniformly, adding tetraethyl orthosilicate to the mixture slowly to obtain gel precursor, placing the gel precursor in drying box to dry at 100-150 degrees C for 2-3 hours to obtain dried gel, baking the dried gel at 550-650 degrees C for 2-4 hours, cooling the gel, placing the gel in muffle furnace, controlling heating rate at 10 degrees C/minute, increasing temperature to 950-1100 degrees C, sintering the gel for 4-6 hours to obtain powder, grinding the powder to 100-200 meshes, adding proper amount of adhesive to the powder, pressing the powder for 3-6 minutes to obtain product, placing the product in muffle furnace, controlling heating rate at 2.5-3.5 degrees C/minute, increasing temperature to 1450-1600 degrees C, and sintering the product at 200-300 MPa for 4-5 hours to obtain the finished product.