A process for the preparation of a ceramic made of an inorganic base material doped by an element J, said inorganic base material having a having a melting point higher than 300°C, said dopant consisting of a single inorganic material or by a mixture of at least two inorganic materials having a doping effect on the inorganic base material, said ceramic being represented by the formula E α-x' k J x' m O β-x'(k-m)/2 2- □ x'(k-m)/2 wherein: - E α k O β 2- denotes the inorganic base material; - E denotes at least one metal from groups I to VIII of the Periodic Table of the Elements, and k denotes the average degree of oxidation of E in the formula I; - J represents at least one metal from groups I to VIII of the Periodic Table, and m denotes the average degree of oxidation of the element J which is partially substituted to E, m is a positive integer such that m < k; - α, k and β are positive numbers being between 1 and 20, such that αk - 2β = 0; - x' denotes the degree of substitution and is a positive number such that x' < α; - □ represents an anionic vacancy; or by one of the formulae M x-x' q J x' m T y n O z-x'(q-m)/2 2- □ x'(q-m)/2 or M x q T y-x' n J x' m O z-x'(n-m)/2 2- □ x'(n-m)/2 wherein: - M x q T y n O z 2- denotes the inorganic base material; - M and T each denote at least one metal from groups I to VIII of the Periodic Table of the Elements, M and T are different; - J represents at least one metal from groups I to VIII of the Periodic Table, - x, y, q, n and z are positive integers such that qx + ny = 2z; - q is the degree of oxidation of M, n is the average degree of oxidation of T, and m is the average degree of oxidation of J; - in formula, 0<x'<x, m<q; - in formula, m<n, 0<x'<y; said process comprising: - a step of mixing the inorganic base material in powder form with an inorganic dopant material in powder form; and - a sintering step carried our at a temperature above 800°C; said process being characterised in that: - the sintering is carried out without prior compaction or by low prior compaction by exerting a pressure of less than or equal to 5 kg/cm 2 on the mixture of inorganic base material and inorganic dopant material powders. - E α k O β 2- denotes the inorganic base material; - E denotes at least one metal from groups I to VIII of the Periodic Table of the Elements, and k denotes the average degree of oxidation of E in the formula I; - J represents at least one metal from groups I to VIII of the Periodic Table, and m denotes the average degree of oxidation of the element J which is partially substituted to E, m is a positive integer such that m < k; - α, k and β are positive numbers being between 1 and 20, such that αk - 2β = 0; - x' denotes the degree of substitution and is a positive number such that x' < α; - □ represents an anionic vacancy; - M x q T y n O z 2- denotes the inorganic base material; - M and T each denote at least one metal from groups I to VIII of the Periodic Table of the Elements, M and T are different; - J represents at least one metal from groups I to VIII of the Periodic Table, - x, y, q, n and z are positive integers such that qx + ny = 2z; - q is the degree of oxidation of M, n is the average degree of oxidation of T, and m is the average degree of oxidation of J; - in formula, 0<x'<x, m<q; - in formula, m<n, 0<x'<y; - a step of mixing the inorganic base material in powder form with an inorganic dopant material in powder form; and - a sintering step carried our at a temperature above 800°C; said process being characterised in that: - the sintering is carried out without prior compaction or by low prior compaction by exerting a pressure of less than or equal to 5 kg/cm 2 on the mixture of inorganic base material and inorganic dopant material powders.